Next Generation Science Level 6 - Textbook A by Blue Ring Media Pty Ltd

Science for the Next Generation

Science Gra d e Si x

Textbook

The 5E Model – Guided Inquiry The Next Generation Science series is based on the Biological Sciences Curriculum Study (BSCS) 5E teaching and learning instructional model. The 5E model is centered on the idea that students understand science concepts best by using prior knowledge to pose questions and find answers through guided inquiry. This hands-on approach, integrated with engineering and design skills, has students learn science by doing science. Teachers guide the learning process and are able to assess student performance by evaluating student explanations and the application of newly acquired knowledge and skills.

Engage

The Engage phase of the 5E model provides students with the opportunity to demonstrate their prior knowledge and understanding of the topic or concept. Students are presented with an activity or question which serves to motivate and engage students as they begin the lesson. Teachers identify and correct any misconceptions and gather data from students which will guide informed teaching and learning. Essential to stimulating and engaging students is the use of mixed media such as colorful photos, illustrations and diagrams found throughout the textbooks and activity books. Next Generation Science also includes extensive digital resources such as narrated videos, interactive lessons, virtual labs, slideshows and more.

Explore

This phase encourages exploration of concepts and skills through handson activities and investigations. Students are encouraged to work together and apply various process skills while gaining concrete, shared learning experiences. These experiences provide a foundation for which students can refer to while building their knowledge of new concepts. This studentcentered phase comes before formal explanations and definitions of the concept are presented by the teacher.

Explain

This phase follows the exploration phase and is more teacher-directed. Students are initially encouraged to draw on their learning experiences and demonstrate their understanding of the concept through explanations and discussion. After the students have had the opportunity to demonstrate their understanding of the concept, the teacher then introduces formal definitions and scientific explanations. The teacher also clarifies any misconceptions that may have emerged during the Explore phase.

Elaborate

In the Elaborate phase, students refine and consolidate their acquired knowledge and skills. Opportunities are provided for students to further apply their knowledge and skills to new situations in order to broaden and deepen their understanding of the concept. Students may conduct additional investigations, share information and ideas, or apply their knowledge and skills to other disciplines.

Evaluate

This final phase includes both formal and informal assessments. These can include concept maps, physical models, journals as well as more traditional forms of summative assessment such as quizzes or writing assessments. Students are encouraged to review and reflect on their own learning, and on their newly acquired knowledge, understanding and skills.

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Next Generation Science Next Generation Science is based on the United States Next Generation Science Standards (NGSS). The series consists of full-color textbooks and full-color activity books for Grades K to 6.

Contact Fo

There are many di on the objects arou when objects are t contact forces. Ap examples of conta

Applied Forc

An applied force object applies forc contact with it. You open and close a twist the lid off a ja

Next Generation Science engages students with a highly visual presentation of the disciplinary core ideas in the textbooks and places an emphasis on applying scientific knowledge using NGSS practices through numerous scientific investigations. Next Generation Science sees engineering as an essential element of science education and as such is tightly integrated into both the textbooks and activity books.

You use applied forces when you press the keys on a keyboard as you type.

Try This! In small groups, discuss examples where applied forces are used to make an object: • • • • • •

The Next Generation Science textbooks include the following features:

Think Deeply

In the Field

Taxonomists Accurately classifying organisms and sharing information on newly discovered species is essential to our understanding of biodiversity. This important job is done by a taxonomist. A taxonomist often works in the field, searching for new organisms and collecting samples that are then taken to a laboratory for closer analysis.

Topic-related questions for group discussion aimed at deepening students’ understanding of the topic.

Goes beyond inquiry by encouraging students to design, model and build to engineer solutions to defined problems.

In the Field Inspirational sciencerelated professions to stir interest in sciencerelated careers.

What are applied fo How do th they are a

start moving change direction speed up slow down stop moving change shape

The girl uses applied forces when she pulls on the string of the kite.

To ensure that organisms all over the world are classified in the same way, taxonomists name, describe and classify organisms according to the International Code of Nomenclature.

Taxonomists often specialize in the search for and classification of certain types of organisms. Some taxonomists specialize in the classification of microorganisms. Others specialize in the classification of specific types of fungi, plants or animals. If you were a taxonomist, what type of organisms would you specialize in? If you found a new species, what would you name it?

A taxonomist determines which family, genus or species an organism belongs to. If it has characteristics different from all known organisms, then that’s where the fun starts! If it belongs to a known genus, then a taxonomist can give a newly discovered species its own species name. If it does not belong to an existing genus, the new organism gets its own two-part scientific name.

Engineer It!

A Closer Look Colonization of Mars

Humans have long been interested in visiting and colonizing another planet. Although we have successfully landed and walked on our moon’s surface, no human has yet to land on another planet. Many scientists believe that this may soon chang29 e. Landing on and coloni zing another planet in our solar system presents a number of problems. Such problems includ e the distance from Earth, composition of the atmos phere, temperature and gravity. In order to find a planet suitable to coloni ze, it would need to be similar to Earth.

The outer planets are not suitable for coloni zation due to their gaseous comp osition and distance from Earth. The two rocky planets closest to the Sun, Mercu ry and Venus, may have some suitable features, but the extremes in tempe rature make them largely unsuitable. That leaves just one potentially suitab le planet – Mars.

A Closer Look Invokes enthusiasm in science by presenting interesting topics beyond the syllabus.

The girl is using a and fly the kite. Th which acts again

Amazing Fact! Interesting facts to build interest and enthusiasm.

orces

ifferent types of forces acting und you. Some forces occur touching. They are called pplied forces and friction are act forces.

Did You Know?

occurs when a person or an ce to another object when in u use applied forces when you door, push a bike up a hill or am jar.

applied forces to pull on the string he wind applies a force to the kite nst the force of gravity.

e some ways you use orces in daily activities? he forces affect the objects applied to?

Try This! Optional hands-on activities to be conducted in groups or at home.

Activity 8.4

Science Words

12.

An organism with a body made up of more than one cell is called a .

13.

An organism with a body made up of just one cell is called a .

Use the words to comp taxonomy species photosynthesis vascular tissue vertebrate

Extra information to build students’ knowledge base of the current topic.

An ice hockey player’s stick is in contact with the puck. The player uses an applied push force on the stick to shoot for goal. The puck accelerates and slides on the ice towards the goal. The goalkeeper uses an applied force in the opposite direction of the motion of the puck. This causes the puck to stop moving. The goalkeeper then strikes the puck with his stick. The applied force sets the puck back in motion in the direction of the applied force.

lete the sentences.

invertebrate unicellular organism multicellular organism organelles

cellular respiration tissue organ organ system

A group of tissues that works together to perfor m a specific function forms an .

During , oxygen interacts with glucose which causes chemical changes that give off energy.

The parts of a cell are

are internal tube-like structures in the roots, leaves of vascular plants stem and .

called

Copy and complete the

table.

Classification of Organ

isms

Kingdom

Characteristics

Archaea

is an animal without a

Example

Eubacteria

backbone.

Protists

is an animal with a backb one.

Fungi Plants Animals

is the process by which light, water and carbo used to produce stored n dioxide are chemical energy in the form of glucose. 8. The process of namin g and classifying organ isms is called . 9. A is a group of similar organ isms that are able to reproduce Althou ghof young Mars is the most the same kind. suitable planet for colonization, many challe nges still exist. These include: 10. A group of similar cells that works function forms • distance from Earth. together to perform the same Using current technology, . it will take about seven month s for a spacecraft to travel 11. Organs thatfrom workEarth toer togeth Mars. to perform a specific function form an . • surface gravity is just 38 percent of that of the Earth’s. 26 • atmosphere consis ts mostly of carbon dioxid e and very little oxygen.

List two unicellular protist s.

How do fungi get the

List two functions of the

In which cell organelle

energy they need to carry out vascular tissue in the

Discussion

life processes?

stem of plants.

does cellular respiration

take place?

Name two organelles that can be found in plant cells but not in animal cells.

Why is a virus not classif ied as a living organism?

• very little liquid water. • toxic soil which is not

Links students to the Next Generation Science Activity Book at the appropriate juncture.

Review 1.

suitable for growing plants

• cold temperatures that are comparable to those at the Earth’s poles. The successful coloni zation of Mars would likely require the establishment of a permanent habitat on the planet’s surface. Get together with your friends and discuss how such a habitat could overcome the challenges of living on Mars.

Review 17

AB Activity

Topical questions at the end of each chapter for formative assessment.

Topic-related questions and situations for class discussion to build a deeper understanding of topics.

Science Words Lists the essential science vocabulary covered in each chapter.

Contents

Unit 1 - Life on Earth Classification Kingdoms Cells Review

Unit 2 - Plants Plant Classification Plant Structures Plant Life Cycles Review

Unit 3 - Animals Animal Classification Vertebrates Invertebrates Animal Systems Review

2 4 8 18 27

30 32 32 40 46 55

56 58 59 65 78 86

Unit 4 - Plant and Animal Adaptations

What Are Adaptations Environmental Adaptations Behavioral Adaptations Adapting to Change Review

90 92 100 104 107

Unit 5 - Ecosystem Interactions Systems and Ecosystems Abiotic Factors Biotic Factors Energy Flow in Ecosystems Review

110 112 116 122 126 139

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Science Skills Scientists ask questions about the world around them. To find the answer to these questions, scientists use special skills to collect, analyze and interpret data. They communicate the things they find out. Let’s look at how you can use these skills so you can be a scientist too.

Observing You make observations when you gather information about something using your senses. You can observe how something looks, feels, sounds, smells or tastes. Scientists often use tools and instruments that allow them to observe things closely. Such tools include hand lenses, microscopes and telescopes. It is important to accurately record your observations in a way that can be easily understood by others. You can make notes, and create charts and tables. You can also draw and label diagrams.

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Comparing and Classifying Scientists compare the things they observe. To compare means to observe the properties or characteristics of two or more things and identify their similarities and differences. Classification is the process of placing things into groups based on similarities in their properties or characteristics. Objects around us can be classified by the properties of the materials they are made of. Organisms can be classified by their features, such as the presence or absence of a backbone.

Measure Measuring is an important science skill. It allows you to quantify your observations. Distance, time, volume, mass and temperature are some quantities that can be measured. To measure accurately, you often need to use tools such as rulers, beakers, thermometers and stopwatches.

Make a Model Scientists often construct models to predict, test and observe real-life phenomena. Models can be physical objects, such a model of a miniature wind turbine to simulate electricity generation or a model of the Earth’s surface to simulate weathering and erosion. Models can also be in the form of diagrams. A food web diagram is a model that shows the flow of energy in an ecosystem. A map is a diagrammatic model of an area of land or water.

Infer You infer when you make a guess about something based on what you know or what you observe. If you see footprints in the snow, you can infer that an animal has passed by after the last snowfall. If you discover an animal jaw bone with large canine teeth, you can infer that the animal likely ate other animals.

Communicate You communicate when you show or tell other people what you find out. Communication can be in the form of a written report, visual displays or an oral presentation.

Scientific Method Scientists ask questions based on observations of the world around them. To find the answers to their questions, they carry out tests and investigations following the scientific method. Why is it useful for scientists to follow the same scientific method?

The scientific method is a logical set of steps that is followed to help guide an investigation. It also helps to ensure the investigation is carried out fairly and in a manner that can be understood and repeated by other scientists.

Make Observations The scientific method begins by making observations about the world around you. You may observe that plants in one area grow faster and taller than plants in other areas. You may notice that you feel hotter in a darker-colored shirt than a lighter-colored shirt. You may observe that ice melts faster in a cup made of one material than a cup made of another material. Such observations lead you to ask questions about why these things occur.

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Ask Questions Before a science investigation begins, it’s important to ask questions about what you would like to find out. Asking questions helps you to define the investigation. Your investigation should be designed to find the answer to your questions. You can also use prior knowledge and experiences to provide possible answers to your questions.

Why does warm water cool faster in a metal cup than in a foam cup? Do plants grow taller when fertilizer is added to soil?

Why do amphibians live near water?

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Make a Prediction Once you have asked questions based on your observations, it’s time to make a prediction and form a hypothesis. A hypothesis is a statement about what you think your investigation will show. A hypothesis is more than just a guess. It is a statement based on knowledge you already have or things you have observed in the past. Based on past gardening experience, you may predict that plants will grow faster and taller in humus-rich potting soil than in sandy soil. Based on a previous investigation, you may already know that metal is a better conductor of heat compared to wood or plastic. These past experiences can help you predict the results of an investigation. Why is it important to write a procedure that can be easily followed by others?

Plan and Carry Out an Investigation Once you have stated your hypothesis, it’s time to plan and conduct an investigation that will test your prediction. In planning your investigation, you should include all the materials you will need and a procedure that clearly shows the steps you will take to conduct the investigation. Your materials and procedure should be written in a way that allows the investigation to be easily followed and repeated by others. In your procedure, include the data you will collect and the way it will be recorded.

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Variables An important part in a science investigation are variables. A variable is any factor that can be controlled or changed during the investigation. There are three main variables – the independent variable, the dependent variables and the controlled variables. The independent variable is the one condition in the investigation that you can change. Usually it is the thing that is being tested. If you were investigating which materials are good conductors of heat, the independent variable would be the type of material. The dependent variable is the factor that you measure or observe. The dependent variable should change due to changes in the independent variable. In an investigation on materials that are good conductors of heat, the dependent variable could be temperature of water in a cup. You would expect the temperature of the water to change as you change the independent variable – the type of material the cup is made of.

Imagine conducting an investigation about the growth rates of different seedlings. What would be the independent variable? What would be the dependent variable?

Imagine you were carrying out an investigation into the effect of temperature on plant growth. What would be your controlled variables?

The controlled variables are variables that do not change during the investigation. Controlled variables could include the type and size of a container, the source and temperature of water and the types of instruments used to take measurements. The purpose of the controlled variables is to ensure that the only influence on changes in your observations is due to the independent variable.

Collecting and Recording Data Make observations and collect data as stated in your procedure. The data should be recorded in an organized way that can be read and understood by others. Often, data is recorded in a visual manner, such as charts, graphs and diagrams. Data can also be entered into computer software which can make it easier to analyze and present the data.

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Analyze and Interpret Data Once your observations have been accurately recorded, it’s time to analyze and interpret the data to see if your hypothesis is supported. You analyze when you look closely at recorded data. You look for patterns to help explain your results. A pattern is when data repeats in a predictable way. You interpret when you understand and explain what the data means. In interpreting data, you use your prior knowledge, experience, and skills to explain patterns and trends identified in the analysis of the data. An important part of analyzing and interpreting is to check the accuracy of the data collected. If there are inaccuracies or inconsistencies in the data, you may need to adjust your procedure and repeat the investigation.

Draw a Conclusion By analyzing and interpreting your data, you reach a conclusion. Your conclusion is a summary of the data collected. Your conclusion should indicate the accuracy of your prediction. Your conclusion should state whether your hypothesis was supported or not supported. If your hypothesis was not supported, you may decide to form a new hypothesis and plan and conduct a new investigation. If your hypothesis was supported, you may wish to do further investigations to confirm the results or improve the accuracy of the data collected.

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Communicate The final step in a science investigation is to communicate your findings to others. This allows you to share what you have discovered and also allows others to assess the accuracy of your investigation. The people you communicate your results with may wish to conduct a similar investigation and compare results. They may also wish to conduct further investigations to find out more. If they do, they’ll also communicate their results so others can learn from their investigations too.

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Scientific Method Flowchart Make Observations

Ask Questions

Construct Hypothesis Plan and Conduct Investigation Analyze and Interpret Data Form a Conclusion Hypothesis Not Supported

Hypothesis Supported

Communicate Results

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Science Safety In the Laboratory

Follow these safety rules when in your science laboratory or when carrying out any science investigation. o not enter the laboratory without D a teacher. ollow your teacher’s instructions. F If you have any questions or are unsure of what to do, raise your hand and ask your teacher. o not eat, drink, play or run in D the laboratory. ash your hands with soap when W entering and before leaving the laboratory. Dry your hands properly, especially if you will be working with electrical equipment. If any chemical or hazardous material gets on your hands, inform your teacher immediately. ear appropriate safety gear when W carrying out scientific investigations. Safety gear includes a lab coat, safety goggles and gloves. Tie long hair back and do not wear open-toed shoes. e careful when handling sharp tools B or working with burners and hot substances.

o not panic if an accident occurs. D Be aware of eyewash stations, fire extinguishers, exit doors and other safety equipment and procedures in case of an emergency. eep your workspace clean and K organized. Report any spills or breakages to your teacher. Clean up any spills straight away and dispose of the cleaning products safely. hen cleaning up, ensure all W materials and substances go into the correct bin or container. Do not pour any liquid down the sink unless your teacher has instructed you to do so. ook after the equipment you use and L return it to its proper location in the same condition you received it. Wipe your workstation down after use.

In the Field ake sure you are accompanied by an M adult when on field trips or doing other activities outside of the schoolyard. n long trips, make sure you take O enough water and food. Bring insect repellent if necessary. n sunny days, take Sun protection such O as a long-sleeved shirt, hat and sunscreen.

Try This! Create a poster of the rules to be followed in your science laboratory or classroom. Display the poster in a place for everyone to see.

o not touch plants, animals or other D organisms unless instructed to do so by your teacher.

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Life on Earth

In this chapter you will ... • describe the ways in which organisms can be classified. • briefly describe the characteristics of the organisms in each kingdom. • list the organelles that make up cells and identify differences in animal and plant cells. • describe the process of cellular respiration. • describe how cells are organized within multicellular organisms.

Why is it important to name, describe and classify organisms into groups?

Go Online! Access interactive content relating to this topic on the NGScience website. ngscience.com

What are the parts and functions of cells?

Think Deeply Scientists classify organisms by their chances of becoming extinct. If an animal is likely to become extinct, it is classified as endangered. Gorillas are classified as critically endangered. Threats to their survival include hunting, habitat destruction and disease. Why is it important to protect endangered animals? What things can people do to reduce their chances of becoming extinct?

Classification To organize and gain a better understanding of organisms, scientists classify them into groups based on shared characteristics. The process of naming and classifying organisms is called taxonomy. Carl Linnaeus was a Swedish scientist and university professor who spent much of his time collecting and studying organisms of all kinds. In 1735, he published a book, called Systema Naturae, that proposed a system for classifying and naming organisms. This system of classification, called binomial nomenclature, is still used by scientists around the world today. Using the same system of classification allows scientists to describe organisms in a precise way. This enables them to easily share their knowledge and discoveries. The broadest and most general group of organisms are called kingdoms. There are six kingdoms recognized by scientists: • • • • • •

archaea eubacteria protists fungi plants animals

The Six Kingdoms of Life Archaea • unicellular • no nucleus • decomposers • can move from place to place

Fungi • unicellular and multicellular • nucleus • decomposers • cannot move from place to place

Eubacteria • unicellular • no nucleus • decomposers • can move from place to place

Plants • multicellular • nucleus • producers • cannot move from place to place

Protists • unicellular and multicellular • nucleus • producers and consumers • some can move from place to place

Animals • multicellular • nucleus • consumers • can move from place to place

Did You Know? Rotifers are amongst the smallest animals on Earth. Most cannot be seen using only your eyes. They form part of zooplankton in aquatic environments. They are able to reproduce rapidly and are an important component in aquatic ecosystem food chains.

By looking closely at the characteristics of organisms, scientists are able to classify them into smaller and smaller groups. Let’s take a look at this classification system by looking at how a lion is classified. Lions belong to the kingdom Animalia which includes all animals – from microscopic invertebrate zooplankton to giant vertebrates such as elephants and whales. At the next classification level for lions is the phylum Chordata. All of the animals in this phylum have a backbone – they’re all vertebrates.

Think Deeply Look at the animals on pages 6 and 7. Identify the animals that belong to the same: • kingdom • class • family • genus

Below a phylum is the class Mammalia. All animals in the class Mammalia are mammals. Mammals are warm-blooded animals with a body covered with hair or fur. Females give birth and feed milk to their young.

Mammals that get their energy by eating mostly other animals are carnivores. They are classified together in the order Carnivora. Within the order Carnivora is the family Felidae. All members of this family are cats – tigers, lions, lynx and domestic cats too. Within the cat family are the big cats – tigers, lions and leopards. These animals belong to the genus Panthera. The smallest unit of classification is a species. A species is a group of similar organisms that are able to reproduce young of the same kind. All species are given a two-part scientific name. The first part of the name is the organism’s genus. The second part of the name is called the specific name. The two-part scientific name for lions is Panthera leo.

Try This! Conduct research to find out the scientific names of some of your favorite animals. Find out what other animals belong to the same order, family or genus.

Go Online! Learn more about binomial nomenclature on the NGScience website. QuickCode: Z3Z6

Activity 1.1

Kingdoms Bacteria Did You Know? An organism that can survive in extreme conditions is called an extremophile. Extremophiles, like archaea, are able to thrive in conditions that most other organisms cannot.

Archaea live in extreme environments including hot springs.

Bacteria (singular bacterium) are amongst the simplest and oldest organisms on Earth. All bacteria were once classified into the same kingdom. However, after a closer look at their genetic makeup scientists agreed they should be divided into two kingdoms – archaea and eubacteria. All bacteria are unicellular microorganisms and most can only be seen using powerful microscopes. Bacteria are unique from other microorganisms in that they do not have a nucleus. Archaea live in extreme environments and are often classified by where they can be found. Such extreme environments include the deep ocean floor, volcanic vents, hot springs and in the intestines of animals.

The bright colors of the Grand Prismatic Spring in Yellowstone National Park, USA is caused by archaea.

Eubacteria are called true bacteria. They can be found in all natural environments – in the air, in water and soil. They also live and reproduce in the bodies of other organisms, including humans. Bacteria reproduce asexually whereby an individual bacterium divides to form two identical daughter bacteria. Reproducing in this way allows bacteria to reproduce rapidly. Bacteria can cause diseases and infections in plants, animals and people. Salmonella and E. coli are bacteria that can cause food poisoning in people and some animals. Bacteria can also be helpful. Many organisms need bacteria to help them get the nutrients they need. Bacteria in your stomach help you to get nutrients from the food you eat.

Trillions of bacteria can be found inside the human body.

Bacteria are often classified by the shape of their unicellular bodies, such as rods, spirals and spheres. Coccus are spherical.

Bacillus are rod-shaped.

Spirillus are spiral-shaped.

Paramecium and many other unicellular protists reproduce by dividing.

amoebas

Protists Giardia duodenalis is a microscopic protist that colonizes the small intestine of humans and can cause diarrhea.

Protists are organisms that belong to the kingdom Protista. Protists are not classified based on the characteristics they share; instead they are classified together because they do not clearly fit into the other kingdoms of life. Protists come in a diverse range of shapes and sizes. Most protists, like plasmodiums, euglenas and parameciums, are unicellular. There are also multicellular protists, such as the giant kelp and slime molds. Unlike bacteria, the cells that make up protists contain a nucleus. Protists live in a diverse range of habitats. They can be found in freshwater and saltwater aquatic environments. They can be found on land, underground and as parasites inside the bodies of other organisms. Why are protists classified into the same kingdom?

kelp

Some protists are plant-like, such as diatoms and euglenas, and are able to photosynthesize. Others are animal-like and obtain energy by feeding on other organisms or by absorbing nutrients from their environment. Amoebas are unicellular protists that engulf and feed on other organisms such as algae and bacteria. Most protists reproduce asexually. But some multicellular protists have more complex life cycles.

slime mold

red algae

mold decomposing bread

Fungi Fungi (singular fungus) include organisms such as mushrooms, puffballs and molds. Most fungi are multicellular and reproduce by releasing microscopic spores into the air. New fungi grow from the spores. Yeasts are unicellular and reproduce asexually by budding whereby a small bud forms and splits off to form a new daughter cell. Bread mold as seen under a microscope.

Go Online! Discover more about fungi in a video on the NGScience website. QuickCode: B7M1

Fungi are decomposers – they get the energy they need by breaking down the remains of other organisms and absorbing the organic matter. You can see this when mold forms on spoiled food.

In nature, fungi break down the remains of plants and animals. In doing so, they play an important role in ecosystems by returning nutrients to the soil. Some fungi can cause diseases in plants, animals and people. Mildews are fungi that decompose the leaves of plants which can limit their ability to photosynthesize. Ringworm and candida are fungal infections that can affect people and other animals. Fungi can also be helpful to people in many ways. Many mushrooms are important food sources. Yeast is used in the preparation of bread and cheese. The medicine penicillin, an important antibiotic, is obtained from the fungus Penicillium notatum.

Activities 1.2 – 1.3

honey fungi in a hollowed log

Try This! If there is a forest in your area, plan a trip with your family or friends to go on a fungi hunt. Take a pencil and notebook and sketch the fungi you spot.

What are the characteristics of fungi?

orchid

Plants Think Deeply Plants are a very diverse group of organisms. What are two characteristics that all members of the plant kingdom share?

Plants are multicellular organisms that get the energy they need by photosynthesizing. Photosynthesis is the process by which light energy, water and carbon dioxide are used to produce stored chemical energy in the form of a sugar called glucose. The glucose is stored by the plant and used to carry out life processes. As primary producers in all ecosystems, plants are important food sources for many other organisms. Most plants are terrestrial, meaning they grow on land. They are usually anchored to the ground by roots. Some plants can grow by attaching themselves to other plants, such as the trunks of trees. Plants can also be found floating or submerged in freshwater aquatic environments. Only a few plants, such as seagrasses and mangroves, can survive in the ocean’s salt water.

underwater seagrass

Plants are a very diverse group of organisms. So far, almost 400,000 different species have been named and classified. Plants can be classified in different ways. They can be classified by how they reproduce, the structures they possess or whether they have vascular tissue. Vascular tissue are internal tube-like structures in the roots, stem and leaves that transport water, nutrients and food around the plant. Plants with vascular tissue are called vascular plants. Angiosperms (flowering plants), gymnosperms (conifers and cycads) and ferns are vascular plants. Plants without vascular tissue are called non-vascular plants. Without structures to transport water, nutrients and food, non-vascular plants are usually smaller in size than vascular plants. Bryophytes, which include mosses, liverworts and hornworts, are non-vascular plants.

Amazing Fact! The Rafflesia is a parasitic plant that in some species produces the largest flowers in the world. Being parasitic, the plant has no roots, stem or leaves. Rafflesia flowers produce a strong odor of rotting meat. This attracts flies and other insects which help in pollination as they fly from flower to flower.

Rafflesia

Activity 1.4 bird of paradise

hawksbill sea turtle

Animals

leafy sea dragon

Animals are a diverse group of multicellular organisms that live in all parts of the Earth. They have a large range of adaptations that allow them to live in a great variety of habitats – from lush tropical forests, the freezing North and South Poles to the dark and deep ocean. So far, about 1.5 million animals have been named and described by scientists and many more are discovered every year. Unlike plants, which get the energy they need through photosynthesis, animals are consumers. They feed on other organisms to get the energy they need. Most animals have body parts that enable them to move from place to place. Many animals also have sense organs to take in information about the world around them. Their sense organs allow them to move in response to changes around them. Animals also move about in search of food, to escape from danger or to find a mate. Animals take in oxygen from the air or water and most reproduce sexually. common toad

rabbit

honeybees

Within the animal kingdom, scientists divide animals into two main groups based on the presence or absence of a backbone. Animals that have a backbone are classified as vertebrates. Many of the animals we are most familiar with, like mammals, birds, reptiles, amphibians and fish are vertebrates. Animals without a backbone are classified as invertebrates. They account for about 95 percent of the animals on Earth. Some invertebrates, like worms and jellyfish, have soft bodies. Others, like insects and crustaceans, have a hard outer covering called an exoskeleton. The exoskeleton provides protection and often helps to prevent water loss.

earthworms

Try This! With a classmate, list some of your favorite animals. Discuss what makes the animals different from other animals.

Without a backbone or internal skeleton of bones, invertebrates are generally smaller in size than vertebrates. What are some characteristics most animals share?

barn owl eyelash viper

Cells There is a great variety of organisms on Earth. From microscopic bacteria and protists to the millions of different plants and animals that inhabit all areas of our planet. Organisms show great diversity in shape, size and the places they live, but all organisms have at least one thing in common – they are made of one or more cells. Cells are the smallest units within an organism that can carry out life processes. They are often referred to as the ‘building blocks of life’.

Acetabularia is a type of unicellular green algae. Each umbrella-like structure is an organism made up of just one cell.

Some organisms are made up of only a single cell. They are unicellular organisms. Others, like most fungi, plants and animals are made up of many cells. They are called multicellular organisms. Humans are multicellular organisms. Scientists estimate that our bodies are made up of trillions of different cells that all play a role in helping our bodies function.

Various cells in the esophagus of a cat as seen under a light microscope.

Most plant and animal cells have the same internal parts, called organelles. Each organelle has a specific role in helping the cell to function as a whole system. Let’s take a look at the parts of an animal cell.

Try This!

Animal Cells Surrounding an animal cell is a cell membrane – a thin layer that surrounds the cell. Its main function is to regulate the interactions that occur between the cell and its external environment. It allows only certain substances to pass in and out of the cell. nucleus

Take a chicken egg and place it carefully into a beaker of vinegar and let it sit for two days. Observe the egg once the shell has dissolved. Discuss which part of the egg cell you are observing. Discuss its properties.

nucleolus cell membrane vacuole Golgi apparatus

animal cell

endoplasmic reticulum (with ribosomes)

mitochondrion

cytoplasm

Inside the cell is the cytoplasm. The cytoplasm is a watery gel-like substance that holds and supports the cell organelles except for the cell nucleus. It helps to protect the organelles and also gives the cell its shape.

nucleus

mitochondrion

The nucleus is often referred to as the control center of the cell. It is a large, round organelle that controls all of the internal cell activities and processes such as growth and metabolism. At the center of the nucleus is the nucleolus which is where ribosomes are made. Mitochondria (singular mitochondrion) are often referred to as the powerhouses of the cell. They break down digested food and release the energy needed to power the cell. The Golgi apparatus is the organelle that packages and transports proteins for delivery to different destinations within the cell.

golgi apparatus

The endoplasmic reticulum (ER) is an organelle attached to the nucleus. Its main function is to produce proteins for the rest of the cell. The protein is made in ribosomes, which are small, round organelles on the surface of the ER. Vacuoles are storage spaces for water, wastes and other cellular material. What are the main functions of the organelles in an animal cell?

endoplasmic reticulum

Plant Cells Like animal cells, plant cells have a cell membrane, nucleus, mitochondria, ER and ribosomes. Plant cells also have vacuoles, but they are usually larger than the vacuoles in animal cells. Like animal cells, the organelles in plant cells float in the cytoplasm. Plant cells are different from animal cells in that they have a cell wall – a rigid structure that surrounds the cell membrane. The main function of the cell wall is to provide support and protection. Many plant cells also contain chloroplasts. Photosynthesis takes place in the chloroplasts. Chloroplasts contain chlorophyll which is a green pigment that captures the energy from sunlight.

Plant cells as seen under a light microscope.

chloroplast

Activity 1.5

Why do plant cells generally have a more regular shape than animal cells?

vacuole

nucleolus

cell wall

nucleus cell membrane

chloroplast

mitochondrion

plant cell

cytoplasm

Golgi apparatus

endoplasmic reticulum (with ribosomes)

Cellular Respiration Like animal cells, plant cells have a cell membrane, nucleus, mitochondria, ER and CellularPlant Respiration ribosomes. cells also have vacuoles, but they areand usually larger in in Plants animals getthan the the foodvacuoles they need animal cells. LikePlants animal cells, organelles different ways. use thethe energy in sunlight intoplant cells float in the cytoplasm. produce food in the form of glucose. Animals eat other organisms for food. To Plant cellsthe areenergy different fromthe animal in release in food, cellscells in plants that haveneed a celltowall – adown rigid structure andthey animals break the glucose that surrounds the cell membrane. The main through a process called cellular respiration. function of the cell wall is to provide support and protection. Cellular respiration takes place in the mitchondria of cells. During cellular respiration, Many plant cells also chloroplasts. oxygen interacts withcontain glucose which causes Photosynthesis takes place in the chemical changes that give off energy. The chloroplasts. Chloroplasts contain chlorophyll energy is used to power the cell. Carbon which is a green pigment that captures the dioxide and water are produced as waste energy from sunlight. products. Plants can use the waste products for photosynthesis. Animals release the waste products into the air when they exhale. What interaction occurs during cellular respiration? What is produced as a result?

Activity 1.6

Cell Organization In unicellular organisms, the single cell itself carries out all of the life processes needed for survival. The many cells that make up multicellular organisms are organized in a way that allows them to work together to perform specific functions. muscle cell

A group of similar cells that work together to perform the same function forms tissue. Muscle is an example of tissue. Muscle is made up of groups of muscle cells. A group of tissues that work together to perform a specific function forms an organ. The heart is an organ made up of different tissues. Its primary function is to pump blood throughout the body. Organs that work together to perform a specific function form an organ system. The circulatory system is comprised of the heart and blood vessels.

muscle tissue

All of the organ systems working together make up an organism. Within our bodies, the skeletal system, muscular system, circulatory system, respiratory system and other systems all work together to help us move about and carry out life processes.

heart (organ)

Activity 1.7 23

A Closer Look

Viruses – Cell Invaders! If you have ever had the flu or the common cold, you’ve had a virus in your body. Viruses are microscopic germs, but they are not classified as living organisms. They are not made of cells, they cannot obtain or store energy and they can only replicate when inside the cells of other organisms. A virus is a strand of genetic instructions surrounded by an outer covering. It can invade and take over the cells of all types of organisms, from animals and plants to microorganisms including bacteria. The cell that is invaded by a virus is called a host cell. Once inside a host cell, the virus releases its genetic material and instructs the host cell to replicate it many times. Host cells can replicate millions of copies of a virus in just a few hours. Once replicated, the host cell bursts open and the newly replicated virus is released. Each new virus can go on to invade other host cells. Most viruses are harmless to people, but some can cause us to get sick. Viruses can cause illnesses such as the common cold, the flu, cold sores and chickenpox.

We get sick from a virus when it infects or kills many of our cells, causing an immune response from our bodies. Often, the virus will infect cells in certain parts of the body. The common cold, for example, is caused by a rhinovirus that affects the nose and throat. The runny nose and sore throat you get when you have a cold is your body’s immune system fighting the infection. Many viruses can only replicate at specific temperatures. A fever is your immune system’s response to fight the virus by increasing your body temperature. A vaccine is a special type of medicine that can be used to help your body fight a virus. A vaccine often contains a weakened, modified version of the virus itself. Rather than causing you to get sick, the vaccine causes your body to produce virus-fighting proteins called antibodies. If the virus enters your body in the future, your immune system already knows how to fight the virus. Because less people get sick when they are vaccinated, vaccines also help to stop the spread of viruses.

envelope genetic material

An artist’s impression of the coronavirus that causes COVID-19.

Vaccines can help your body fight off viruses.

Did You Know? A pandemic is the name given to a viral or other infectious disease that has spread worldwide. In 2020, there was a pandemic due to the spread of a virus called SARS-CoV-2 which caused the infection COVID-19. The virus infected the lower airways and lungs. People infected had symptoms such as a dry cough, difficulty breathing and mucus in the lungs. The virus mainly spread through tiny droplets released into the air when a person exhales, coughs or sneezes. What things can people do to prevent a virus such as COVID-19 from spreading?

Science Words Use the words to complete the sentences. taxonomy species photosynthesis vascular tissue vertebrate

invertebrate unicellular organism multicellular organism organelles

cellular respiration tissue organ organ system

1. A group of tissues that works together to perform a specific function forms an . 2. During , oxygen interacts with glucose which causes chemical changes that give off energy. 3. The parts of a cell are called 4. An 5. A

is an animal without a backbone. is an animal with a backbone.

6. are internal tube-like structures in the roots, stem and leaves of vascular plants. 7. is the process by which light, water and carbon dioxide are used to produce stored chemical energy in the form of glucose. 8. The process of naming and classifying organisms is called 9. A is a group of similar organisms that are able to reproduce young of the same kind. 10. A group of similar cells that works together to perform the same function forms . 11. Organs that work together to perform a specific function form an .

12. An organism with a body made up of more than one cell is called a . 13. An organism with a body made up of just one cell is called a .

Review 1. Copy and complete the table. Classification of Organisms Kingdom

Characteristics

Example

Archaea Eubacteria Protists Fungi Plants Animals 2. List two unicellular protists. 3. How do fungi get the energy they need to carry out life processes? 4. List two functions of the vascular tissue in the stem of plants. 5. In which cell organelle does cellular respiration take place? 6. Name two organelles that can be found in plant cells but not in animal cells. 7. Why is a virus not classified as a living organism?

In the Field

A taxonomist determines which family, genus or species an organism belongs to. If it has characteristics different from all known organisms, then that’s where the fun starts! If it belongs to a known genus, then a taxonomist can give a newly-discovered species its own species name. If it does not belong to an existing genus, the new organism gets its own two-part scientific name.

To ensure that organisms all over the world are classified in the same way, taxonomists name, describe and classify organisms according to the International Code of Nomenclature. Taxonomists often specialize in the search for and classification of certain types of organisms. Some taxonomists specialize in the classification of microorganisms. Others specialize in the classification of specific types of fungi, plants or animals. If you were a taxonomist, what type of organisms would you specialize in? If you found a new species, what would you name it?

Plants

In this chapter you will ... • list the ways in which plants can be classified and the characteristics that define the plants in each group. • list the types and describe the function of vascular tissue. • construct an argument and provide evidence that plants have internal and external structures that function to support survival, growth and reproduction. • compare and contrast flowering and non-flowering plants by the stages in their life cycles.

How are plants classified? What are the characteristics of the plants in each group?

How do a plant’s internal and external structures help it survive?

Go Online! Access interactive content relating to this topic on the NGScience website. ngscience.com

How are plants different in the ways they reproduce?

Plant Classification Plants are a very diverse group of organisms. Approximately 400,000 species have been named, described and classified by scientists and thousands of new species are discovered every year. With such biodiversity comes the need to classify plants into groups based on shared characteristics. Scientists do this in a number of ways. One way plants are classified is as vascular plants or non-vascular plants. Vascular plants have vascular tissue – internal, tube-like structures to transport water, minerals and food throughout the plant. Non-vascular plants do not have vascular tissue. Plants can also be classified by how they reproduce. Non-vascular plants and ferns do not produce seeds – they are seedless plants. They reproduce from spores. The spores are typically made of just one cell. Each spore is capable of developing into a new organism. In mosses, spores are contained in a capsule. In ferns, spores are usually located on the underside of the fronds in clusters called sori. What four plant groups are represented in the photographs on this page?

Gymnosperms, such as conifers and firs, are cone-bearing plants. They reproduce from seeds held in cones. Angiosperms are flowering plants. They reproduce from seeds that develop in flowers and are held in fruits.

Mosses

Liverworts

Non-vascular Plants

Plant Kingdom Vascular Plants

Ferns

Gymnosperms

Hornworts

Go Online! Discover more about classification and diversity within the plant kingdom on the NGScience website. QuickCode: B3G2

Angiosperms

Activity 2.1 33

Non-vascular Plants

Did You Know? Many mosses are pioneer species. A pioneer species is one of the first organisms to grow in an area with little or no other plants. As more pioneer species grow, weather rocks, then die and decay, soil begins to form and the environment becomes suitable for a greater diversity of organisms.

If you walk along a forest stream, chances are you will spot mosses. Mosses are non-vascular plants. They do not have vascular tissue – xylem and phloem – to transport substances throughout the plant. They also lack true roots, stems and leaves. To survive without vascular tissue, non-vascular plants are small and live close to the ground. They absorb the water and nutrients they need from their environment. The water then travels within the plant by moving from one cell to the next. Mosses, liverworts and hornworts are the main groups of non-vascular plants. Non-vascular plants have root-like structures called rhizoids that anchor them in place. They can often be seen carpeting the moist forest floor, clinging to rocks or growing on the trunks of trees.

liverwort

Mosses and liverworts have tiny leaf-like parts called leaflets which are just one-cell thick. Most photosynthesis occurs in the leaflets. Non-vascular plants are seedless plants. They reproduce from single-celled microscopic spores held in a part called the capsule. When the capsule opens, the spores are spread by water and wind to new places. Under the right conditions, new plants will grow from the spores. Why are mosses small in size and found mostly in moist environments?

moss capsules containing spores

A Closer Look

Parts of a Moss Plant

capsule sporophyte

seta

foot

leaflets

gametophyte

rhizoids

phloem

xylem

Vascular Plants Imagine visiting your local park or garden. What plants would you see? How are the plants different? In what ways are they similar? Almost all of the plants you spot in a park or garden are similar in that they are vascular plants. Vascular plants are plants that have tube-like vascular tissue to transport food, water and waste throughout the plant. There are two main types of vascular tissue – xylem and phloem. Xylem transports water and nutrients, usually from the roots to the upper regions of the plant. Phloem transports food from the leaves to all parts of the plant.

Cross-section of a sunflower stem as observed under a microscope.

xylem

The cells in vascular tissue are rigid and provide plants with support, allowing them to grow taller than non-vascular plants. phloem

water food

mosquito fern

tree fern

Vascular plants can be further classified based on whether they produce seeds and where the seeds form. Ferns are a diverse group of seedless vascular plants often identifiable by the feather-like leaves called fronds. The smallest of ferns, the mosquito fern, has fronds that are just a few millimeters in length. The largest of ferns is the tree fern which can reach heights of more than 20 meters and have fronds up to three meters in length. Ferns reproduce from spores which are usually held on the underside of the fronds. The spores are dispersed by wind and water.

Fern spores are held in enclosures called sporangia on the underside of fronds.

Think Deeply Why can ferns grow much larger than mosses?

Horsetails are another kind of seedless vascular plants that reproduce from spores which are usually held in capsules.

Activity 2.2

In most horsetails, spores are held in capsules.

giant sequoia

Did You Know? Gymnosperms are the oldest seed-producing plants. Fossil evidence suggests they first appeared on Earth about 320 million years ago. Angiosperms, the other main group of seed-producing plants, first appeared about 135 million years ago.

ginkgo tree

Plants that reproduce from seeds are called seed plants. The two main types of seed plants are gymnosperms and angiosperms. Gymnosperms are non-flowering plants. They reproduce from seeds, but do not produce flowers or fruits. The word gymnosperm means ‘naked seed’ as the seeds are not enclosed in an ovary, but instead sit on the surface of leaf-like structures called bracts. The bracts form the reproductive organ called a cone. The largest group of gymnosperms are conifers which include pines and cypresses. Some of the oldest and tallest plants are conifers, including the most massive tree on Earth, the giant sequoia. Other gymnosperms include cycads and ginkgos.

Angiosperms are flowering plants. They produce seeds that are held in the ovaries of flowers. As the seed develops, the ovary forms a protective fruit around the seed. Angiosperms are the most diverse group of plants. More than 300,000 different species have been named and classified which accounts for approximately 80 percent of all known plant species. Angiosperms have a range of adaptations that allow them to live and grow in all areas of the Earth. Many angiosperms are an important source of food for humans and other animals. All grasses, grains, fruits and vegetable plants are angiosperms. As are tulips, sunflowers, oaks and maples.

Try This! Botanical gardens and parks are a great way to observe plant biodiversity. Plan a visit with your family or friends. Classify the plants into groups.

Plant Structures Roots All of the roots of a plant make up its root system. In most vascular plants, the root system is underground. The root system has three main functions:

vascular tissue

• take in water and minerals from the soil. • hold the plant in the soil. • store food. root hair

root hair

root cap

The outer layer of a root is called the epidermis. Attached to the epidermis are tiny roots hairs which are just one-cell thick. The root hairs absorb water and minerals which are transported from the root to the upper parts of the plant. At the tip of a root is a root cap. It helps to protect the root as it grows down into the soil.

Running through the center of roots are vascular bundles which contain xylem and phloem. Xylem transports water and minerals through the roots to the upper parts of the plant, called the shoot system. Food is transported from the shoot system to the roots in phloem vessels. Plants can have different roots that help them in different ways. Some roots are shallow and branch out to cover a large area. These roots, called fibrous roots, help the plant to take up lots of water when it rains. Branching out over a large area also helps to anchor the plant in place. phloem

xylem

root hair

epidermis root section

Other plants have one main root, called a taproot, which grows deep into the soil. It allows the plant to reach water deeper in the soil. Some plants have roots that grow above ground, called aerial roots. An epiphyte is a plant that grows on another plant, often on the trunks of trees. Many ferns and orchids are epiphytes. Their aerial roots take in rainwater and water vapor from the air. Some epiphytes are also able to take in moisture through their leaves.

AB Activities 2.3 – 2.4 41

Stems The stem is usually the part of the plant that connects the root system to the upper portions of the plant. The stem provides support for the plant. It holds up the leaves allowing them to spread out and take in more sunlight. It also supports the reproductive structures. Stems contain vascular tissue that transports substances throughout the plant. Xylem vessels transport water and minerals from the root system to the leaves. Phloem vessels transport food from the leaves to all parts of the plant. xylem

epidermis

phloem

stem section

Some plants use their stems for storage. Bamboo and sugarcane store food in their stems. Many cacti store water in their stems.

tomato plant

What are the main functions of the stem?

Some plants, such as the tomato plant on the previous page, have green stems that are thin and can bend more easily than others. They are called herbaceous stems. A plant with a herbaceous stem is called a herbaceous plant. Herbaceous stems get their green color from chloroplasts in the cells. Vegetable plants such as tomatoes, beans, peppers and herbs have herbaceous stems. A soft and flexible herbaceous stem cannot support the weight of the extensive shoot system of a tree. Trees are plants with thick, strong stems covered in bark. They do not bend easily. These stems are called woody stems. A plant with a woody stem is called a woody plant Many shrubs also have woody stems. Woody stems are usually brown in color. The cells in woody stems do not contain chloroplasts. The bark surrounding woody stems provides protection against diseases and extreme weather. In cold regions, plants with woody stems survive through the colder months, but may lose their leaves to conserve energy. Plants with herbaceous stems may die back to soil level before re-emerging in the warmer months.

How does the bark surrounding a woody stem help the plant?

Activity 2.5

Leaves Leaves are structures that are highly specialized to carry out photosynthesis. They are often flat, broad and branch out in all directions to maximize their surface area. This enables them to absorb as much sunlight as possible. Running through a leaf are veins containing vascular tissue. Xylem vessels deliver water that has moved from the roots, through the stem to the leaves. Food produced during photosynthesis is transported from the leaves to all parts of the plant in phloem vessels. The top of a leaf is a layer of cells called the epidermis. A waxy covering on the epidermis, called the cuticle, helps to prevent water loss due to evaporation. On the underside of a leaf are many tiny openings called stomata (singular stoma). Air, including the carbon dioxide needed for photosynthesis, enters the leaf through the stomata. cuticle

epidermis palisade layer

vein

stoma

phloem leaf anatomy

xylem

Below the epidermis is a layer of cells called the palisade layer. Cells in this part of the leaf contain many chloroplasts which are the organelles that carry out photosynthesis. Inside the chloroplasts, light energy absorbed by the green pigment chlorophyll combines carbon dioxide and water to produce sugar in the form of glucose. Oxygen is produced as a by-product. The glucose provides the plant with the energy it needs to carry out life processes.

Watch photosynthesis in action in an animated video on the NGScience website. QuickCode: S7S2

The oxygen produced during photosynthesis is released into the air through the stomata.

Go Online!

Activities 2.6 – 2.7

sunlight

water

sugar

oxygen carbon dioxide

During photosynthesis, plants use the energy in sunlight to convert water and carbon dioxide into sugar and oxygen.

Plant Life Cycles Non-vascular Plant Life Cycle Non-vascular plants are seedless plants with a life cycle that involves both asexual and sexual reproduction. Let’s look at the life cycle of non-vascular plants by looking at the stages in the life cycle of mosses. In the asexual phase, spores are produced and held in a capsule. When the capsule breaks open, the spores are released into the air. They are spread to new places by wind or moving water.

moss sporophytes

spores released

sporophyte

Under the right conditions, a single spore will germinate and grow into a leafy gametophyte. The gametophyte has male and female parts. Fertilization occurs when a sperm cell from the male part fuses with an egg cell in the female part. The fertilized egg will develop into a new moss sporophyte. The sporophyte will produce spores held in capsules and the life cycle continues.

Activities 2.8 – 2.9

leafy gametophytes

gametophyte

germinating spore

fertilization

Fern Life Cycle Ferns are seedless plants that reproduce from spores. Like the life cycle of mosses, the life cycle of ferns involves two distinct phases – an asexual phase and a sexual phase. In the asexual phase, spores form in clusters on the underside of mature fern fronds. The spores are held in cases called sporangia. Once the spores are developed, the sporangia breaks open and the spores are dispersed by wind and moving water. fern spores held in sporangia

sporangia

sporophyte

mature sporophyte

Under the right conditions, a single spore will germinate and grow into a heart-shaped plant called a gametophyte. Root-like rhizoids anchor the gametophyte to the ground. The gametophyte has both male and female parts. Sperm cells make their way from the male part to the female part and fuse with female egg cells. The fertilized egg cell develops into an embryo. It eventually grows larger than the gametophyte and becomes a sporophyte. The sporophyte produces spores and the two-phase life cycle repeats.

Activities 2.10 – 2.11

gametophyte with rhizoids developing

spores released

gametophyte

fertilization

Gymnosperm Life Cycle The reproductive structures on gymnosperms are cones. Male cones contain pollen with sperm cells inside and female cones contain eggs cells. Usually, the female cones are larger and are found in the upper regions of a gymnosperm tree. Male cones are smaller and are found mostly in the lower regions. Pollination occurs when pollen grains, usually blown by wind, are transferred from the male cone to the female cone. female cone with eggs

male cone with pollen

mature gymnosperm

sapling emerges

The pollen grain develops a pollen tube allowing a sperm cell to reach and fertilize an egg cell. The fertilized egg cell then develops into a seed. Mature seeds are usually dispersed by wind to new places. Under the right conditions, each seed will grow into a sapling before growing into a mature tree with reproductive cones and the life cycle repeats. pollen grain develops pollen tube

Male cone releasing pollen into the air.

sperm cell fertilizes egg cell

seed develops

seeds disburse

AB Activity 2.12 51

Angiosperm Life Cycle Angiosperms are flowering plants. They reproduce by sexual reproduction whereby male sex cells, called sperms, unite with female sex cells, called eggs. Pollination occurs when pollen grains from the anther are transferred to the stigma of a flower. This can occur within the same flower, and also between two flowers of the same species. When a pollen grain lands on the stigma, it produces a pollen tube that grows into the stigma, through the style to the ovary. Inside the ovary are ovules. Each ovule contains an egg cell. A sperm cell moves from the pollen grain on the stigma, through the pollen tube to the ovary. Fertilization occurs when the sperm cell reaches and fuses with an egg cell.

pollen is released

Compare and contrast the stages in the life cycles of mosses, ferns, gymnosperms and angiosperms.

sperm moves down pollen tube

sperm fertilizes egg cell

Following fertilization, the flower petals fall away and the ovule begins to develop into a seed. The ovary of the flower swells to form a protective fruit. Once developed, the seeds need to be dispersed to new places. This can occur when animals feed on fruits or when seeds and fruits stick to their bodies. Fruits and seeds can also fall away and be carried to new places by wind or water. In its new location and under the right conditions, the seed will germinate and grow into an adult plant.

Activities 2.13 – 2.14

seed is dispersed and germinates

fertilized ovule develops into a seed

Science Words Use the words to complete the sentences. vascular plants non-vascular plants seedless plants gymnosperms 1.

angiosperms xylem phloem fibrous roots

taproot aerial roots herbaceous plant woody plant

are plants that do not produce seeds.

2. transports water and nutrients, usually from the roots to the upper regions of the plant. 3.

transports food from the leaves to all parts of the plant.

4. A

has a soft, flexible green stem.

5. A

has a thick, strong stem covered in bark.

6. One main root which grows deep into the soil is called a 7. Plants that contain vascular tissue are called

. .

8. Plants that do not have vascular tissue are called

9. an ovary.

are seed-producing plants with seeds not enclosed in

10. in ovaries.

are seed-producing plants with the seeds enclosed

11. Roots that grow above ground are called 12.

are shallow and branch out to cover a large area.

Review 1. Create a Venn diagram to compare mosses and ferns.

Mosses

Ferns

2. Create a Venn diagram to compare gymnosperms and angiosperms.

Gymnosperms

Angiosperms

3. Draw a simple labeled diagram to show the function of vascular tissue in the stem of a plant. 4. What is the function of stomata? Where are they mostly found? 5. What do plants need to photosynthesize? What is produced as a result? 6. What is the name given to the spore-producing asexual phase in the life cycle of mosses and ferns? 7. What role does a fruit play in the reproduction of angiosperms?

Animals

In this chapter you will ...

• list the ways in which animals can be classified and the characteristics that define the animals in each group. • construct an argument that animals have internal structures that function to support survival.

How are animals classified? What are the characteristics of the animals in each group?

Go Online! Access interactive content relating to this topic on the NGScience website. ngscience.com

What internal structures do animals have that function to support their survival?

Animal Classification

A salamander is a vertebrate.

A garden snail is an invertebrate.

Animals are classified into two main groups – vertebrates and invertebrates. Vertebrates are animals with a segmented backbone. Vertebrates also have an internal skeleton that supports and protects their bodies. Specialized collections of bones, such as the skull and rib cage, help to protect vital organs. Fish, amphibians, reptiles, birds and mammals (including humans) are vertebrates. Most of the animals on Earth, about 95 percent, are invertebrates. Invertebrates are animals that do not have a backbone. Sponges, jellyfish, sea stars, snails and arthropods are invertebrates. Animal Kingdom

Vertebrates

Invertebrates

hammerhead shark

lampreys

Vertebrates

lionfish

Fish There are three main groups of fish – jawless fish, cartilaginous fish and bony fish. Jawless fish are the oldest and simplest group of fish that include lampreys and hagfish. They do not have jaws and feed by sucking their food. Sharks, rays and skates are cartilaginous fish. Their internal skeleton is made of cartilage which is strong and flexible. This provides support and protection and enables many cartilaginous fish to grow larger than other types of fish. Bony fish have an internal skeleton made of bone. They include many of the fish you are most familiar with including salmon, tuna and swordfish. Sea dragons and eels are also bony fish. Fish are ectothermic (cold-blooded), which means their body temperature is dependent on their environment. Fish reproduce by external fertilization whereby sex cells are released and fertilized in water. All fish are aquatic animals and are well-adapted to living in water. They usually have streamlined bodies covered in scales, fins for swimming and gills to take in oxygen from water. About 35,000 different species of fish have been named and classified.

Activities 3.1 – 3.2 59

Amphibians There are three main groups of amphibians – caecilians, salamanders and frogs (including toads). Caecilians are limbless amphibians with dark, smooth skin. They are found mostly underground or in rivers and streams. Salamanders are amphibians that are similar in appearance to lizards. They have long, slender bodies with a tail. poison dart frog

Amazing Fact! Poison dart frogs are a group of frogs native to South America that come in a range of bright colors. They produce and secret a toxin that, in some species, has enough poison to kill more than 10 people. Scientists are unsure how the frogs produce poison but some suggest it is due to their diet of ants and mites.

Frogs are amphibians we are most familiar with. They often have short bodies with powerful hind legs for moving about on land and in water. Toads are similar in appearance to frogs, but often have drier and rougher skin. About 8,000 different species of amphibians have been named and classified, out of which about 90 percent are frogs. Frogs are ectothermic with their body temperature dependent on that of the environment. Reproduction on most amphibian species involves external fertilization.

spotted salamander

A Closer Look

Life Cycle of a Frog The life cycle of amphibians is truly fascinating. Let’s take a closer look at an amphibian life cycle by looking at the life cycle of the common frog. Females lay eggs in water. The young that hatch from the eggs, called larvae or tadpoles, do not resemble their parents and are well-adapted to living in water. They have a tail to help them swim and gills to take in oxygen from water. Gradually, the larvae undergo metamorphosis – a change in body form. adult frog

eggs

froglet

larva (tadpole)

larva with hind legs

About eight to 10 weeks after hatching, the tadpoles begin to develop hind legs, then forelegs. Their tails also begin to shrink. By around 14 weeks, their tails are almost completely gone and their gills have developed into lungs. At around 15 to 16 weeks, the young frogs move onto land. They will go on to find a mate and the life cycle continues.

larva with hind and forelegs

Go Online! Watch a video on the life cycle of frogs on the NGScience website. QuickCode: M4Q4

Activity 3.3 61

Reptiles Reptiles, of which more than 11,000 species have been named and classified, can be divided into three main groups: • crocodiles and alligators. • snakes and lizards. • turtles.

grass snake with eggs

Think Deeply Why do you often see reptiles, such as lizards and turtles, lazing motionless under the Sun throughout the day?

Reptiles are ectothermic with bodies covered in scales or plates. The majority of reptiles live on land, but some live in the ocean or freshwater habitats. All reptiles get the oxygen they need from air using lungs. Reptiles reproduce sexually and have internal fertilization. This means the eggs are fertilized inside the body of the female. Most reptiles lay eggs from which young hatch. However, a few species of snakes, such as vipers, give birth to live young.

Activity 3.4

Being ectothermic, many reptiles spend a lot of time basking in the Sun.

Birds Birds are a diverse group of endothermic (warm-blooded) vertebrates. Endothermic means they are able to regulate their own body temperature so it remains relatively constant. More than 10,000 bird species have been named and classified. They range in size from the tiny five-centimeter bee hummingbird to the giant ostrich which can reach heights of almost three meters. Birds’ bodies are covered in feathers. All birds also have two wings, two feet and a beak or bill. With light bodies and powerful muscles, many birds use their wings to fly. There are about 60 species of flightless birds, including emus, cassowaries and penguins. Birds reproduce by internal fertilization whereby the egg cells are fertilized inside the female bird. Hard-shelled eggs then develop and are laid in a nest. The eggs are kept warm and are cared for by the parents until the young hatch from each egg.

emu with her chicks

Go Online! Discover the diversity within the bird kingdom on the NGScience website. QuickCode: X1Q1

Once hatched, most birds care for their young. They provide them with warmth, food and protection from predators.

eagle owl

Activity 3.5 63

pipistrelle bat

Mammals Many of our most familiar animals are mammals. Mammals include monkeys, bats, cats, deer and bears. More than 6,400 mammal species have been named and classified. Mammals are endothermic. Females give birth to live young with the exception of two Australian animals, the echidna and platypus, which are egg-laying mammals. Female mammals have mammary glands which produce milk for feeding their young. Female mammals feed milk to their young.

Mammals have lungs and take in oxygen when they breathe in air. Aquatic mammals, such as dolphins, sea lions and whales, must come to the surface to breathe. Adult mammals often care for their young until they are old enough to survive on their own. They may teach their young how to find food or hunt. They may also teach them how to stay safe from other animals.

Activity 3.6

Invertebrates Invertebrates are the largest group of animals. More than 1.3 million species have been named and classified, which make up 97 percent of all known animals on Earth. They have no backbone or internal skeleton. Without the support and protection of bones, many invertebrates are smaller in size than vertebrates, although many large invertebrates can be found in the ocean. Many invertebrates have soft, flexible bodies with a tough outer covering for protection and to reduce water loss. Most invertebrates reproduce sexually with the young hatching from eggs. The young often look very different from their parents. Some invertebrates, particularly arthropods, undergo changes in body form as they grow – a process called metamorphosis.

Activity 3.7

Sponges

Cnidarians

Worms

Invertebrates Echinoderms

Mollusks

Arthropods

Sponges barrel sponge

Sponges are some of the world’s oldest and simplest animals. About 5,000 species have been named and classified. Almost all sponges live in the ocean, with 150 freshwater species found in lakes. Sponges are asymmetrical multicellular organisms. They do not have body parts, tissues or organs. They reproduce both sexually and asexually via budding. Sponges are filter-feeders. They pump water through the holes in their bodies called pores. As water moves through the pores, bacteria and tiny particles are taken up from the water as food. Adult sponges are sessile, which means that they do not move about and are fixed in one place. They rely on a continual flow of water through their bodies to obtain food and oxygen and to remove wastes.

Go Online! Watch a video on the life cycle of sponges on the NGScience website. QuickCode: V5J3

tube sponge

Cnidarians Cnidarians are simple organisms that include corals, jellyfish and anemones. About 9,000 different species have been named and classified. Most cnidarians are marine organisms, although a few species live in freshwater environments. Some cnidarians, like jellyfish, are attached to the sea floor in the early stages of their life cycle but are free-swimming as adults. Others, such as corals and anemones have free-swimming larval stages but are sessile as adults. Most cnidarians reproduce sexually, whereby sex cells are released and are fertilized in water. Some corals are also able to reproduce asexually by budding. Unlike sponges, cnidarians have radial symmetry. This means their bodies are arranged around a central point with more than one line of symmetry.

Anemone fish seek shelter in sea anemones.

Did You Know? Some cnidarians, such as certain species of box jellyfish, produce a strong venom. The sting can be very painful and has been known to be fatal to humans.

A unique characteristic of cnidarians is the presence of stinging cells called cnidocytes. Cnidocytes contain a toxin that can stun and capture prey. They are also used for defense against predators. Some jellyfish produce toxins that are harmful to people.

Activity 3.8

A Closer Look

Life Cycle of a Jellyfish Jellyfish have a complex and unique life cycle that involves both a sexual and an asexual phase. In the sexual phase, adult jellyfish are free-swimming and have an umbrella-like shape called a medusa. Male jellyfish release sperm cells into the water which fertilize eggs cells released by females. A fertilized egg cell develops into a larva called planula that attaches itself to the sea floor. As it matures, it develops into a polyp and enters the asexual phase of the life cycle. The polyp the reproduces by budding whereby young medusas are released into the water. They will mature into adult medusa jellyfish and the life cycle continues. adult medusa jellyfish

fertilized egg

young medusa

planula larva

polyp budding polyp

Worms Worm is the general name given to animals from three different groups – flatworms, roundworms and segmented worms. The worms in each group have bilateral symmetry and most reproduce sexually. Flatworms belong to the phylum Platyhelminthes, of which there are about 20,000 different species. They are the oldest and simplest of worms with soft, flat bodies that have no circulatory or respiratory systems. They take in oxygen and nutrients directly from their surroundings. Flatworms can be found in salt water, fresh water and damp land environments. Most flatworms however (about 80 percent) are parasitic, living inside other organisms. Roundworms belong to the phylum Nematoda, of which about 25,000 have been named and described. Nematodes are more advanced than flatworms. They have a tubular digestive system with openings at both ends. Roundworms live in a range of different environments. Many are parasitic and can cause illnesses and diseases in other organisms.

marine flatworm

Amazing Fact! Many worms are hermaphrodites. This means they have both male and female reproductive organs. During reproduction, a hermaphrodite can play the role of the male or the female.

Nematode as seen under a microscope.

leech

Try This! Use a hand lens to observe the body of an earthworm. Make a rough sketch of its segmented body.

Activity 3.9

tube worm

earthworms

Segmented worms belong to the phylum Annelida, of which there are about 22,000 species. Common segmented worms include earthworms, leeches, tube worms and bristle worms. Segmented worms get their name from their bodies which are divided into segments. Segmented worms are the most advanced of the three types of worms. They have organ systems including circulatory, digestive and nervous systems. Segmented worms have a range of adaptations that allow them to live in a variety of environments. They can be found in the intertidal zones of the ocean, underwater vents and freshwater environments. Some are terrestrial, living in moist environments on land. How are segmented worms different from other worms? bristle worms

sea cucumber

sand dollars

Echinoderms Echinoderms are animals in the phylum Echinodermata, of which there are about 7,000 named species. Common echinoderms include sea stars, sea urchins and sea cucumbers. All echinoderms live in the ocean, from warm tropical reefs to the Earth’s icy poles. Most echinoderms have radial symmetry and reproduce sexually. However, some can also reproduce asexually. Echinoderms produce a hard internal structure which gives their outer covering a rough, spiny appearance.

Think Deeply Imagine you spotted an invertebrate with radial symmetry on the sea floor. What features would help you identify it as an echinoderm?

AB Activity 3.10 Tube feet on the underside of a sea star.

Echinoderms move about using a system of tube feet. This allows them to crawl slowly on the ocean floor. What characteristics do echinoderms share? sea urchin

sea stars

Mollusks Mollusks are animals within the phylum Mollusca, which is the second largest invertebrate group with around 85,000 named species. Most mollusks can be placed into three main groups – cephalopods, gastropods and bivalves. Cephalopods are marine animals that include octopuses, squid and cuttlefish. They are thought to be the most intelligent of all invertebrates. Their large and welldeveloped brain and tentacles make them very efficient predators. Gastropods are a diverse group of animals that make up about 80 percent of all mollusks. Many gastropods, such as snails and limpets have a hard outer shell. Others, such as slugs and sea slugs do not have a shell. Bivalves have bodies enclosed by a shell consisting of two hinged parts. Common bivalves include clams, oysters, mussels and scallops. Most mollusks live in the ocean and make up about 23 percent of all named marine organisms. Some also live in fresh water or terrestrial environments. What characteristics do cephalopods share?

The soft body of mollusks contains tissues and organs to carry out life processes. They have digestive, respiratory and circulatory systems. Most mollusks have a specialized mouth structure called a radula which is a series of tiny teeth used for scraping food particles into the mouth. Mollusks also have a muscular organ, called a foot, which is used to move about. eye upper tentacle (ocular) shell lower tentacle (olfactory) mouth

tail

AB foot

Activity 3.11

external anatomy of a garden snail

A common characteristic of mollusks is a mantle in the form of a shell. Snails and limpets are examples of mollusks with one shell. Clams and scallops have two shells which are hinged on one side. This allows the shell to open and close. All mollusks have bilateral symmetry. All mollusks reproduce sexually which involves the fertilization of male and female sex cells.

Try This! If resources are available, use a hand lens to observe a terrestrial mollusk, such as a garden snail or slug. Describe its features. Use a spray bottle of water and a cotton swab to observe how it responds to stimuli.

Some mollusks, such as the blue-ringed octopus and the cone snail, produce venoms which can be fatal to humans.

barnacles

Atlantic blue crab

Arthropods Arthropods, organisms of the phylum Arthropoda, are the most diverse and numerous group of animals with more than one million species named and described. They make up over 80 percent of all known animal species. They live in all areas of the Earth – from the deep ocean to hot, dry deserts and moist tropical rainforests. American lobster

emperor scorpion

Arthropods can be divided into four main groups – insects (bees, ants and beetles), arachnids (spiders, scorpions and mites), myriapods (millipedes and centipedes) and crustaceans (crabs and lobsters). Arthropods have a hard outer body covering called an exoskeleton. Made of chitin, the exoskeleton supports and protects the animal’s body and can also help reduce water loss. Arthropods have paired limbs on each side of their segmented bodies. Some arthropods have modified limbs in the form of claws or wings. praying mantis

termite

jumping spider

An exoskeleton does not bend easily. To move about, arthropods have many joints which allow them to bend parts of their bodies. Without an internal skeleton to support their bodies, arthropods are usually small in size. Aquatic arthropods, such as crabs and lobsters, are often larger than land arthropods as they are able to use the surrounding water for support.

ladybug

Think Deeply Molting is the process whereby arthropods shed their exoskeleton and grow a new one. Why must arthropods molt as they mature?

Arthropods have organs and body systems for digestion, breathing, circulation and reproduction. They also have a variety of different sense organs, such as eyes and antennae. All arthropods have bilateral symmetry and reproduce by sexual reproduction. What characteristics are common to all arthropods?

centipede

Engineer It! Arthropods have a diverse range of body shapes that allow them to live in a great variety of habitats. Identify a human problem that can be solved by mimicking the body shape or parts of an arthropod. Draw a model to show how your design solves the problem.

Activities 3.12 – 3.13 75

A Closer Look

Insects Insects are the largest and most diverse group of arthropods. Approximately one million species of insects have been named, described and classified. This represents more than half of all known organisms on Earth. Common insects include beetles, flies, bees, grasshoppers and butterflies.

common housefly

The defining characteristics of insects include an exoskeleton, a body divided into three segments, three pairs of jointed legs, compound eyes and one pair of antennae.

adult swallowtail butterfly

In the life cycle of most insects, the young do not resemble their parents. As the young grow and mature, they undergo changes in body form – a process known as metamorphosis. As young insects grow, they usually go through a series of molts whereby they shed their exoskeleton and form a new one. swallowtail eggs

swallowtail pupa

swallowtail larva

Head The head of an insect holds its sense organs which include eyes and antennae. The head also contains the insect’s mouth parts which are adapted and suited to the types of food it eats.

Thorax The center body part of insects is the thorax. It holds three pairs of legs and in mature, flying insects, also holds one or two pairs of wings.

Abdomen The abdomen is located behind the thorax. At the rear of the abdomen is the anus, which is the rear opening of the digestive system where wastes are removed. In some insects, such as bees and wasps, the abdomen also contains a stinging organ.

Antennae Antennae are sense organs usually located at the front of the head. They often contain smell receptors which allow insects to detect smells. In some insects, the antennae can also detect changes in humidity – the amount of water vapor in the air.

Compound Eyes Most insects have compound eyes. Compound eyes consist of thousands of tiny light receptors that work together to enable insects to see.

Wings Insects are the only arthropods with wings. Most insects have two pairs of wings. The outer wings are often used for protection and the inner wings used for flight.

Animal Systems What are some body systems of animals? What is the function of each system?

Structure and Support Most animals move from place to place in search of food and to escape from danger. To do this, most animals have internal or external structures for support and protection.

bigfin reef squid

Many invertebrates, such as arthropods, have an exoskeleton – a hard outer coating that protects their soft bodies. The exoskeleton is made of a substance called chitin. Muscles at joints pull on the exoskeleton which enables them to move. Exoskeletons also help to reduce water loss. Animals without exoskeletons can also use muscles to move about. An earthworm moves by contracting its muscles in waves. Squid and octopuses use muscles to push water out of their bodies which propels them in the opposite direction.

earthworm

muscles

praying mantis

Vertebrate animals – mammals, birds, reptiles, amphibians and fish – have an internal structure of connected bones that forms an internal skeleton, called an endoskeleton. The bones are hard and rigid and provide the vertebrates with shape, support and protection. Collections of bones within the endoskeleton, such as ribs and skulls, also provide protection for vital organs. Muscles are attached to bones. When these muscles contract, they pull on the bones. This enables the animal to move.

AB Activity 3.14

endoskeleton of a sparrow

Amazing Fact! Many birds have hollow bones with criss-crossing structures. This gives their lightweight skeleton extra strength. Air sacs in the hollows also allow them to take in more oxygen.

A tiger’s muscular and skeletal systems work together to allow movement and provide protection.

Gas Exchange Some animals, such as flatworms, do not have internal structures for taking in the oxygen they need. Instead, oxygen diffuses into their bodies directly from the air around them. Snails, slugs and some amphibians also get the oxygen they need in this way. Most animals have internal structures to help them get the oxygen they need from their surroundings. The same structures also get rid of the carbon dioxide which animals produce. In fish and many aquatic invertebrates like marine worms, crabs, squid and clams, taking in oxygen and removing carbon dioxide take place in gills. When water washes over the gills, oxygen moves into the blood and carbon dioxide moves from the blood to the water. Insects have openings in their exoskeletons called spiracles. The spiracles can be opened to take in oxygen and closed to reduce water loss.

direction of water flow

Birds and most other land vertebrates have lungs to take in oxygen from the air. lung air sac

Mammals, birds and reptiles have lungs to take in oxygen from the air when they inhale. In the lungs, the oxygen passes into the blood where it is transported throughout the body. Carbon dioxide passes from the blood and is removed from the body when the animal exhales. Aquatic mammals and reptiles also have lungs. To take in oxygen and remove carbon dioxide, they must come to the surface to breathe in air.

Think Deeply Getting caught in discarded fishing gear and other marine debris can be fatal to marine reptiles and mammals. Why is this so?

In the cells of all animals, oxygen is used to release the energy in digested food. This process is called cellular respiration. During cellular respiration, carbon dioxide and water are produced as waste products.

AB Activity 3.15

blowhole

Air moves into and out of a dolphin’s lungs through a blowhole. lung

Blood Circulation All vertebrates and some invertebrates have internal structures to move blood throughout their bodies. Central to these structures is the heart. The heart is an organ made mostly of muscle. When the muscles in the walls of the heart contract, blood is pumped through the heart and around the body. Many invertebrates, such as insects, have an open circulatory system. In an open circulatory system, there are no blood vessels to transport blood. Instead the heart pumps oxygenated blood into a central cavity. When the animal moves, the blood moves around the cavity and gives the tissues, organs and cells the oxygen they need. Wastes are also passed from the cells back into the blood. All vertebrates and some invertebrates, such as earthworms, have a closed circulatory system. In a closed circulatory system, blood is distributed to and from the heart in blood vessels. Compare and contrast the circulatory systems of grasshoppers and earthworms.

heart Open circulatory system of a grasshopper.

heart

blood vessel

Closed circulatory system of an earthworm.

Vertebrates have an open circulatory system. Some vertebrates, such as fish, have a single-loop circulatory system. In such a system, oxygenated blood moves in blood vessels from the heart to the gills and is then distributed to the tissues throughout the body. Wastes are then transported back to the heart and leave through the gills. Birds and mammals have a double-loop circulatory system. Using a four-chambered heart, blood moves in one loop between the heart and the lungs and in another loop between the heart and the rest of the body.

AB Activity 3.16 Compare and contrast the circulatory systems of fish and mammals.

lung capillaries

gill capillaries

heart

body capillaries

Single-loop circulatory system of a fish.

Double-loop circulatory system of a mammal.

Amazing Fact! The stomach is an important organ in the digestive system of most vertebrates. The arrangement and size of the stomach depends largely on the vertebrate’s diet. Deer and other large herbivorous mammals have large stomachs with four chambers. This helps them to digest the grasses and other plant parts they eat. A few vertebrates, such as seahorses, have no teeth or stomach. Food passes directly to the intestines. Food moves through their digestive system so quickly that seahorses are constantly eating.

Digestion To get energy from food, the food first needs to be broken down into simple substances that can be absorbed into the bloodstream and distributed to cells. This process, called digestion, occurs in different ways in different animals. In some simple invertebrates, such as jellyfish and flatworms, food enters and waste leaves the animal through the same opening. More complex animals, including all vertebrates, have a complete digestive tract. The digestive tract is a series of tubes with two openings – a mouth to take in food and an anus to remove waste. Digestion occurs in these animals as the food passes through a series of organs specialized in breaking the food down into simpler substances. Such organs include the stomach and intestines. The digestive system and the arrangement of digestive organs differ between animals depending on their diets.

AB Activity 3.17

The digestive system of a fox.

Science Words Use the words to complete the sentences. vertebrate invertebrate ectothermic endothermic

external fertilization internal fertilization endoskeleton gills

lungs open circulatory system closed circulatory system digestion

1. are internal structures used to take in oxygen from the air and remove carbon dioxide. 2. are internal structures used to take in oxygen from water and remove carbon dioxide. 3. A 4. An

is animal with a backbone and internal skeleton. is an animal without a backbone.

5. An animal is warm-blooded and is able to regulate its body temperature. 6. An animal is cold-blooded with a body temperature that is dependent on its environment. 7. An is an internal structure of connected bones that provides vertebrates with shape, support and protection. 8. The process by which food is broken down into simple substances and absorbed into the bloodstream is called . 9. In a blood vessels. 10. In an

, blood is distributed to and from the heart in , the heart pumps blood into a central cavity.

11.

is where sex cells are released and fertilized in water.

12. is where sex cells are fertilized inside the body of the female animal.

Review 1. List some characteristics of fish that make them well-adapted to aquatic environments. 2. How are reptiles different from birds in terms of body temperature regulation? 3. List two vertebrate animals groups whereby reproduction involves internal fertilization. 4. List two vertebrate animals groups whereby reproduction involves external fertilization. 5. List the three main types of fish. 6. Which group of amphibians are limbless and have dark, smooth skin? 7. List the three main groups of reptiles. 8. True of false.

(a) (b) (c) (d)

All birds have feathers. All birds use their wings to fly. Birds are ectothermic. All birds have bilateral symmetry.

9. List the defining characteristics of mammals. 10. List two invertebrate groups with radial symmetry. 11.

Of the three main worm groups, which are the oldest and simplest?

12. To which invertebrate group do cephalopods belong? Provide two examples of cephalopods. 13.

List the defining characteristics of insects.

14. Describe how vertebrates use their internal structures to help them to move. 15. Provide an example of an animal with: (a) a closed circulatory system. (b) an open circulatory system. (c) a single-loop closed circulatory system. (d) a double-loop closed circulatory system. 16. Label the diagram. (a)

(b)

Plant and Animal Adaptations What is an adaptation? How can adaptations help organisms survive in their environment?

Go Online! Access interactive content relating to this topic on the NGScience website. ngscience.com

How can living in groups help animals survive in their environment?

In this chapter you will ... • provide examples of plant and animal adaptations to various environments and explain how they help the plants and animals survive. • construct an argument and provide evidence that in a given habitat, some organisms can survive well, some survive less well, and some cannot survive at all. • provide examples of behavioral adaptations in animals. • construct an argument and provide examples of how some animals form groups that help members of the group survive.

What Are Adaptations? Go Online! Go online and take a virtual field trip to the Arctic. Discover the variety of adaptations of Arctic organisms that help them survive in the cold and dry climate. QuickCode: S2S4

Did You Know? Female polar bears nurse and care for their young when they are born. The cubs remain close to their mother for up to three years, learning how to hunt and stay safe in the cold Arctic environment.

At the Earth’s North Pole, the climate is very cold and dry. During winter, the average temperature drops to below -30oC (-22oF) and there is very little rainfall. The conditions are so harsh that few organisms can survive there. The organisms that live and reproduce in the North Pole have specialized adaptations that help them survive. An adaptation is a physical trait or behavior that helps an organism survive. Polar bears are well-adapted to living in the North Pole. Their thick, white fur allows them to blend in well with the snow and ice that dominates the landscape. Below the fur is a thick layer of fat, called blubber, which helps to keep them warm. To help their young survive, pregnant female polar bears dig dens in the snow. In the den, they give birth and raise their cubs for the first few months until they are able to leave the den. Female polar bear with her cubs.

They have large paws that help to propel them through water. The paws also help to distribute their load on snow and large claws help them to grip on the ice. Polar bears have a number of adaptations that make them fierce predators. They use their keen sense of smell to detect their favorite food, ringed seals, from large distances away. They use strategic stalking skills to sneak up on prey, or sometimes lay in wait at the seals’ breathing holes. Sharp claws and teeth and a powerful jaw help them to catch, kill and eat their prey. In a given habitat, some organisms can survive well, some survive less well, and some cannot survive at all. Often, a species can only be found in one type of habitat. This is because organisms have adaptations that allow them to survive in certain environmental conditions. Populations of polar bears can only be found in the Arctic Circle. They are not adapted to survive in different climates such as those in forests and deserts.

guard hairs fur black skin blubber connective tissue muscle Section of polar bear muscle, skin and fur.

Polar bears preying on seals at a breathing hole in sheets of sea ice.

Think Deeply Large areas of sea ice in the Arctic are essential for the survival of polar bears. They rely on the sea ice for stalking and hunting seals in spring and fall in order to store fats for the winter. Based on evidence, scientists have discovered that human activities are causing the Earth’s average temperature to increase at a faster rate than normal. This is causing sea ice in the Arctic to melt faster in the spring and form later in the autumn. How does this affect the polar bear population and the Arctic ecosystem?

Activity 4.1 91

Environmental Adaptations Organisms can be found in all regions of the Earth – from the icy North and South Poles to hot, dry deserts and warm tropical forests. All organisms have adaptations to survive in their environment. Desert plants and animals have adaptations for living in a dry and often hot environment. Tropical rainforest plants and animals have adaptations for surviving in a humid, moist and warm environment.

Desert Adaptations A desert is a barren environment that receives very little precipitation. It may only rain a few times a year and it is often hot during the day and much cooler at night. Not many plants can live in deserts. Those plants that do have adaptations to survive with little water. They have deep roots that can take in water from deep in the soil. Others have shallow roots that spread out over a large area. This enables them to take in as much water as possible when it rains.

The saguaro cactus has shallow roots that spread out over a large area.

The velvet mesquite bush has deep roots.

In a hot and dry climate, reducing water loss is important. In plants, water loss occurs mostly through the leaves. To reduce water loss, many desert plants have small leaves with a thick and waxy cuticle. A variety of cacti are well adapted to living in deserts. They store water in their stems which are protected from thirsty animals by modified leaves in the form of spines. The spines do not contain chloroplast and most photosynthesis takes place in the stem. Desert animals have a variety of adaptations to survive in hot weather with little water. If you visit a desert during the day, you will not see many animals. Most desert animals are nocturnal. This means they rest and are inactive during the day and are active at night when the temperature is much cooler. Some animals also seek shelter in burrows to help them stay cool. Fennec foxes are nocturnal desert animals. They have large ears to help to radiate body heat and keep them cool. Thick fur helps to keep them warm during cold nights.

Try This! With a classmate, list some of the challenges faced by desert plants and animals. Discuss the adaptations that allow them to overcome these challenges.

fennec fox

Female polar bear with her cubs.

The small five-toed jerboa is a nocturnal desert rodent.

Another reason you may not spot many desert animals during the day is camouflage. Camouflage is an animal’s ability to blend in with its environment. This can help it hide from predators and sneak up on prey. Camels are well-adapted to surviving in deserts. They have a hump on their backs which stores fat for energy. They can also survive for many months without drinking water. A Western diamondback rattlesnake camouflaged in the sandy soil of the Sonoran Desert.

Camels have large, flat feet that spread their weight on the sand. They have thin, narrow nostrils and two rows of eyelashes to help keep out sand. A camel’s tough lips enable it to feed on prickly desert vegetation.

Camels have a number of adaptations that help them survive in desert environments.

Activity 4.2

What are some other examples of desert plants and animals? What adaptations help them to survive in deserts?

Tropical Rainforest Adaptations Unlike deserts, tropical rainforests are home to a great diversity of plants and animals. They are the most biologically diverse ecosystems on Earth. However, with high diversity comes lots of competition for resources such as water, nutrients and sunlight. Rainforest trees have thick woody trunks that allow them to grow to great heights. The trunks lift the leaves high in the sky to take in sunlight. The leaves branch out in all directions. The thick layer of dense leaves, called the canopy, blocks much of the sunlight from reaching the forest floor. Plants below the canopy have adaptations for photosynthesizing in low light. Many rainforest plants have leaves with large surface areas to take in more sunlight. Epiphytes are plants that grow attached to other plants. In tropical rainforests, ephiphytes, like bird’s-nest ferns and orchids, get more sunlight by growing attached to the trunks of trees.

green viper snake

Tropical rainforests are home to thousands of different kinds of animals. With such diversity of both predators and prey, being camouflaged can help an animal stay safe or catch its food. Green viper snakes and tree frogs use camouflage to hide from other animals. A leaf insect blends into its habitat by looking a lot like a leaf.

leaf insect on green leaves

Some tropical rainforest animals rely on mimicry to stay safe. Mimicry is when an animal imitates or acts like another organism, usually for protection against predators. The variable poison frog is a poisonous species of frog that predators avoid. Another, less toxic species of frog, called the mimic poison dart frog, looks almost identical. This helps it to survive as predators are unable to distinguish between the two species. How do camouflage and mimicry help animals survive in a tropical rainforest?

variable poison frog

mimic poison frog

Young spotted owlets seeking the safety of a tree hollow.

Many rainforest animals have adaptations that help them get specific types of food. This helps to reduce competition with other animals. Spider monkeys spend almost their entire lives high in the rainforest canopy and emergent layer. They swing effortlessly from tree to tree feeding on a variety of fruits that other animals cannot reach. Rainforest birds have beaks or bills of all shapes and sizes. A toucan has a large bill that helps it to cut fruits from trees. Parrots have a strong beak to break open seeds and nuts. Nocturnal owls have large eyes to see at night and use their powerful wings and sharp claws to catch and kill their prey.

spider monkey

Activity 4.3 toucan

Tundra Adaptations Go Online! Go online and take a virtual field trip to a tundra to discover more about the adaptations of the organisms that live there. QuickCode: D3P3

Most tundra plants, like these berries, grow close to the ground.

A tundra is a habitat that is very cold all year round. It is often windy and there is not enough precipitation for tall plants and trees to grow. The ground in a tundra often contains permafrost, which is a layer of soil just below the surface that is permanently frozen. With freezing cold air temperatures, little rainfall and permafrost, few plants are able to survive in a tundra. Plants are often small and live close to the ground. Many plants live close together and have a hair-like coating on their leaves. This helps to protect them from the wind and helps to trap heat close to the plants and keep them warm. Different plants have different adaptations to grow in soil containing permafrost. Some have shallow roots that spread out over a large area. Other push their roots through the permafrost to reach the groundwater deeper in the soil. Tundra plants have small leaves to reduce water loss. Some tundra plants are deciduous and lose their leaves during the colder months to conserve energy. Why are tall trees unable to survive in a tundra climate? Hair-like structures on the leaves and stem of low-lying tundra plants help to keep them warm.

Tundra animals have adaptations for living in the cold. Tundra mammals usually have a thick layer of fur. Many also have a layer of blubber for further insulation. Many mammals are large in size, which also helps to prevent heat loss. The few birds that live in the tundras have thick feathers for insulation. Some birds have two layers of feathers. Caribou, also called reindeer, are large mammals that are well-adapted to living in tundras. Their large bodies are insulated by two layers of fur. Fur on the bottom of their hooves helps prevent them from slipping on snow and ice. During the warmer months, caribou feed on tundra plants. During the colder months, they switch to a diet of lichen. In their digestive system are specialized bacteria that help them to get energy from lichen.

Activity 4.4 Caribou nursing her offspring.

snowy owl

Amazing Fact! Many Arctic tundra birds are migratory, meaning they move to warmer climates during winter. The snowy owl is one of the few bird species that can survive the icy Arctic tundra all year round. This is due largely to its thick cover of feathers that even covers its toes. It feeds mostly on small tundra rodents, but can also adapt to feed on many other prey when food is scarce.

Amazing Fact! Most salmon hatch and mature in bodies of fresh water such as rivers and lakes. They then make their way to the ocean where they spend most of their life. Mature adults then make their upstream journey to spawn at the very place they hatched. Many salmon die soon after spawning, meaning a salmon usually completes just one return migration in its life cycle.

Sandhill cranes breed and raise their young in Northern USA in spring. During the winter months, they migrate thousands of kilometers south where the winters are less cold.

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Behavioral Adaptations Along with physical adaptations such as body parts and body coverings, many animals also have behaviors that help them to survive and reproduce. These behaviors are called behavioral adaptations.

Migration and Hibernation In many regions of the world, the climate changes throughout the year. There may be changes in temperature, precipitation and vegetation that make the environment unsuitable for certain organisms. One behavioral adaptation to these changes is migration. Migration is the movement of animals from one place to another. Migration often occurs due to changes in seasons whereby animals move to a new place during some seasons, then migrate back during other seasons. Being able to fly great distances, many bird species migrate seasonally. This often involves animals living in northern regions of the Earth during summer, then migrating south during the winter months. They migrate back to their northern homes in the spring.

Wildebeests crossing the Mara River in Tanzania during the Great Wildebeest Migration.

One of the largest migrations of animals in groups is the Great Wildebeest Migration. Throughout the year, more than two million wildebeests, zebras and gazelles move in a circular pattern as they follow green pastures from the Serengeti in Tanzania to the open grasslands in Kenya. In one year, the animals move more than 800 kilometers. Rather than move from place to place as seasons change, some animals hibernate during the winter months. During hibernation an animal enters a state of minimal activity, much like a deep sleep. The animal’s body temperature, breathing rate and heart rate decrease to conserve energy. For protection against the cold and predators, hibernation usually occurs underground or in secluded shelters. Some bears, skunks, snakes and woodchucks are examples of animals that hibernate.

The migratory path of wildebeests, zebras and gazelles during the Great Wildebeest Migration.

Amazing Fact! Woodchucks are seasonal hibernators. During hibernation, a woodchuck’s body temperature drops from around 37oC (98oF) to just over 3oC (38oF). Its heart rate drops from 80 beats per minute to just 4 to 5 beats per minute.

Activities 4.5 – 4.6

How do migration and hibernation help animals survive in their environment?

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Emperor penguins in the Antarctic form groups to provide insulation from the cold air temperatures and strong winds.

Living in Groups To improve their chances of survival, many animals live in groups. Living in groups is a behavioral adaptation. Animals in cold habitats often form groups to help them stay warm. Emperor penguins live in one of the coldest habitats on Earth – the Antarctic. Temperatures get as low as –50°C (–58°F) and there are very strong winds. During winter, the penguins huddle together in tightly-packed groups. This allows them to conserve heat and also provides protection from the strong winds. The penguins rotate between the inner area where it’s warmer, to the outer areas where it’s much colder. Pack hunters are predators that search for and hunt prey in groups. Hunting in a pack increases the chances of catching prey. When the prey is caught and killed, the food is shared between the members of the group. Lions, cheetahs, wolves and hyenas are pack hunters.

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Living in groups can help animals defend against predators. In the African savanna, lions often prey on elephants. For protection, the elephants roam the savanna in groups. While the lions may be able to catch an elephant on its own, attacking a group of elephants poses a much greater risk of getting injured or killed by other elephants in the group.

gannet colony

Living in groups also help the elephants detect predators faster and over a greater area. This gives the group more time to flee or defend themselves as a group. Living in large groups can make it easier for animals to find a mate and reproduce. Older members of the group can also help raise each other’s young. This allows time for different members of the group to go off in search of food, knowing their young are safe. Young animals benefit from living in groups as they are able to learn from other group members. They may learn to hide from predators or hunt for food. Young animals in groups often play with each other. In doing so, they develop the skills they will need to survive as adults.

Activity 4.7

Discuss the advantages of animals such as baboons living in groups. troop of baboons

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Adapting to Change Did You Know? Orangutans are large primates that live in the tropical rainforests of Indonesia and Malaysia. Due to wide-scale deforestation to make way for palm oil plantations and farmland, about 80 percent of their natural habitat has been destroyed in the past 20 years. If current rates of deforestation continue, orangutans could become extinct within the next 20 years. As a class, discuss some things people can do to prevent the orangutan from becoming extinct.

Ecosystems are constantly being changed. They may change due to natural hazards, such as fire, drought or flood. Changes can also occur due to human activities, such as the clearing of natural areas to make way for the construction of farmland, roads and cities. Pollution also changes ecosystems. Pollution can occur when harmful substances are added to the air, water or land in an ecosystem. When an ecosystem changes, both the abiotic and biotic factors can be affected. Sometimes, the organisms are able to adapt and overcome the changes. They may change their diet or move to a different part of the ecosystem and return when conditions are favorable again. In ecosystems that are permanently changed, such as the building of cities, animals may adapt by eating food scraps left by people or seeking shelter in man-made structures.

orangutans

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In many cases, particularly when the changes are permanent or occur rapidly, the organisms in a changed ecosystem are unable to adapt to the changed conditions. Animals may move to new places. Those animals that are not able to find a suitable new habitat or cannot move on fast enough, may die. Organisms anchored in place, such as most plants and fungi often die. Habitat destruction occurs when an organism’s habitat is changed in such a way that the organisms that live there cannot survive. Habitat destruction usually occurs as a result of human activities. Habitat destruction can drastically reduce the number of organisms in a population. If habitat destruction continues, a species may become threatened or endangered. An endangered species is at risk of becoming extinct. When the last remaining individual of a species dies, the species becomes extinct and no longer exists.

Activity 4.8

Go Online! Observe the impact of rapid changes to ecosystems on the organisms that inhabit them in a video on the NGScience website. QuickCode: Z4F6

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Science Words Use the words to complete the sentences. adaptation nocturnal camouflage epiphyte 1. 2. A 3.

mimicry permafrost behavioral adaptation migration

hibernation habitat destruction endangered species extinct

is the movement of animals from one place to another. animal is active at night and usually rests during the day. is an animal’s ability to blend in with its environment.

4. A species becomes

when none of its kind exist.

5. A behavior that helps an animal to survive and reproduce in its environment is a . 6. is a layer of soil just below the surface that is permanently frozen. 7. is when an animal imitates or acts like another organism, usually for protection against predators. 8. An is a physical trait or behavior that helps an organism survive in its environment. 9. A species that is at risk of becoming extinct is an

10. occurs when an organism’s habitat is changed in such a way that the organisms that live there cannot survive. 11. During like a deep sleep.

, an animal enters a state of minimal activity, much

12. A plant that grows attached to other plants is called an

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Review 1. Why do some organisms survive better than others in a given habitat? 2. List two adaptations of polar bears that help them survive at the Earth’s North Pole. 3. List two adaptations that help polar bears catch and kill their prey. 4. Provide an example where a plant is adapted to live in a desert in terms of: (a) its roots. (b) its stem. (c) its leaves. 5. How does being nocturnal help an animal survive in a desert? 6. Provide an example where an animal is camouflaged in its environment. 7. List two adaptations plants on a rainforest floor have to survive in a low light environment. 8. How does mimicry help an organism to survive in its environment? 9. Provide an example whereby a group of animals undertake migration to help them survive. 10. How does hibernation help an organism survive? 11. Provide an example whereby living in groups helps animals to: (a) stay warm. (b) catch prey. 12. What can happen to the populations in an ecosystem when the ecosystem changes rapidly?

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A Closer Look

Migration of the Arctic Tern One of the most fascinating examples of mass migration is that of the Arctic tern. These birds live in large groups called colonies. During the warm summer months in the Arctic, the terns reproduce and raise their young. As winter approaches and the days get shorter, the colony begins to migrate south, following the pattern of warm and sunny weather. Over the course of a few months, the terns fly from the Arctic to the Antarctic. In a straight line, this distance is about 30,000 km (18,600 mi), but the terns do not migrate in a straight line. They often change their course to follow favorable weather patterns or places where food is more plentiful.

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By placing trackers on the birds, scientists discovered that some colonies fly more than 90,000 km (56,000 mi) in their return trip to and from Antarctica – the greatest migration distance covered by any animal. In one scientific study on the migration patterns of Arctic terns, a tag was attached to the leg of a chick in the north of the United Kingdom in summer. The bird was spotted in Melbourne, Australia, three months later. It had traveled a total of 22,000 km which is equivalent to about 250 km per day. The main diet of Arctic terns is small fish and shrimp. As they migrate, they stop along the way diving and skimming for their meals. By following favorable weather, the birds are able to spot and catch prey more easily in the clear and sunny sky.

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Ecosystem Interactions What makes up an ecosystem? What interactions take place between the components of an ecosystem?

Go Online! Access interactive content relating to this topic on the NGScience website. ngscience.com

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In this chapter you will ...

• list and describe the abiotic and biotic factors of ecosystems. • describe how ecosystems are organized. • develop a model to describe the movement of matter among plants, animals, decomposers and the environment. • develop a model to demonstrate how the amount of energy available to organisms changes in a food chain.

How does energy flow between organisms in an ecosystem?

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Try This! A bicycle is a good example of a system. Make a list of the different parts and functions of a bicycle. Discuss what happens if one part does not function as it is supposed to.

Systems and Ecosystems A system is a group of interacting or interrelated parts that work together to function as a whole. Your body is a good example of a system. Your body has different organs, such as your heart, lungs and intestines. Each organ has a role to play. Your heart pumps blood throughout your body. Your lungs help you get the oxygen you need and also remove carbon dioxide from your body. Your intestines help you to digest food. All of your organs work together to make your body function as a whole.

Your body is made up of a number of different systems that help your body function as a whole.

The parts in a system are interrelated in many ways. For the system to function as a whole, each part must play its role.

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How do the living and non-living parts that make up a pond ecosystem interact with each other? pond ecosystem

An ecosystem is a system in nature where all of the parts – living and non-living – interact with each other for the environment to function as a whole. An ecosystem can be small, such as a pond in a park. An ecosystem can also be very large, such as a desert that stretches for hundreds of kilometers. All ecosystems have two main components – living components and non-living components.

desert ecosystem

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The living components of an ecosystem and the ways in which they affect the environment around them are called biotic factors. Biotic factors include the plants, animals, fungi and bacteria in an ecosystem. In a temperate forest ecosystem, a biotic factor such as the number of tall trees may affect the availability of shelter for birds and small mammals. The different types of animals interact with each other when they compete for resources such as food and water.

red squirrel

What biotic factors would affect the deer living in a forest ecosystem?

Fallow deer in a temperate forest ecosystem.

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desert ecosystem

The non-living components in an ecosystem are called abiotic factors. The abiotic factors include all of the things that enable the biotic factors to survive in the environment. Abiotic factors include water, sunlight, temperature and soil. The abiotic and biotic factors can be very different in different ecosystems. In all ecosystems, the interactions of the biotic and abiotic factors make the ecosystem function. If there are changes in the biotic or abiotic factors, the whole ecosystem may change as a result.

Compare and contrast the biotic and abiotic factors in a desert, grassland and forest ecosystem.

grassland ecosystem

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Abiotic Factors Water

Water is essential to all life on Earth. The availability of clean, fresh water has a large influence on the components of an ecosystem. Plants need water to make food during photosynthesis. Plants also use water to transport food and minerals to all parts of the plant. The amount of water in an ecosystem therefore affects the abundance and diversity of plants in an ecosystem. Generally, ecosystems with high precipitation in the form of rain will support a greater diversity of organisms. In a rainforest, it rains all year round. A great diversity of plants, animals and fungi thrive in these moist conditions. Many organisms live in bodies of water within ecosystems.

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In deserts and tundras, there is much less water available. Organisms in these ecosystems often have adaptations to survive with little water.

All animals need water to survive. Water is used for the transportation of nutrients and oxygen, temperature regulation and the removal of wastes. Most animals get the water they need by drinking water. Some animals get water from the food they eat. In some ecosystems, animals live in bodies of fresh water such as streams, rivers, lakes and ponds. Water can also play an important role in the reproduction of many insects and amphibians.

Activity 5.1

Water plays an important role in amphibian reproduction.

How would the organisms in a pond ecosystem change if the water dried up?

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Sunlight hits the Earth more directly at the equator. At the poles, sunlight spreads over a larger area and is more sparse.

Sunlight

Sunlight is an important abiotic factor that affects all ecosystems as it provides the energy needed by plants for photosynthesis. As the Earth is spherical in shape, the amount of sunlight striking the Earth differs with distance from the equator. At the equator, sunlight strikes the surface of the Earth the most directly. Ecosystems in areas near the equator often contain the greatest diversity of plants and animals and other organisms.

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At the poles of the Earth, sunlight is spread over a wider area. Ecosystems in these areas receive less direct sunlight and there is less diversity of organisms. The Earth’s tilt on its axis as it orbits the Earth causes seasons. As the seasons change, areas near the poles experience great variability in the amount of sunlight they receive. There are more hours of daylight in summer and fewer hours of daylight in winter. The changes in the hours of daylight (and temperature) affect the life patterns of many organisms.

Think Deeply In the deep ocean, there is no sunlight. How does this affect a deep sea ecosystem?

Along with temperature, changes in the length of daylight can trigger deer to reproduce in the spring.

Decreasing hours of daylight means winter is approaching. This may trigger plants to begin to lose their leaves. Animals may begin to move to warmer places. Increasing hours of daylight indicates the end of winter and the start of spring. Ecosystems change as plants regrow their leaves and animals reproduce. During winter, areas near the North Pole have very few hours of daylight. Few plants and animals can survive.

How do changes in the hours of daylight through the seasons affect the plants and animals in an ecosystem?

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The Gobi Desert has great variations in temperature between day and night.

Temperature Ecosystems on Earth can be very different in terms of temperature and this can have a large influence on biotic factors. Most organisms require a stable temperature. In ecosystems around the equator, the temperature does not change much from day to night or throughout the year. The diversity of plants and animals in these areas is often high. In ecosystems further from the equator, there can be large differences in temperature from day to night and as the seasons change. Fewer plants and animals in these areas can survive in the fluctuating temperatures. Ecosystems around the poles of the Earth are very cold all year round. Few plants can survive in these areas.

Antarctica is the coldest place on Earth. Very few plants and animals can survive there.

leopard seal

What adaptations help animals survive the cold Antarctic climate?

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Activity 5.3

Soil and Minerals Soil covers most of the Earth’s land. Soil is a combination of weathered rock, minerals and humus. Humus is organic material formed by the breaking down of dead plants and animals by microorganisms. Between the soil particles are spaces called pores that hold water and air. Soil also contains microorganisms and may contain animals such as worms and insects. In ecosystems, soil is an important abiotic factor for plants. Plant roots grow into the soil which hold them in place. Plants also take in water and minerals from the soil. Some animals, such as earthworms, live in soil.

Some organisms, such as earthworms, live in soil.

The soil in different ecosystems can have different characteristics. It can be different in the amount of humus, nutrients, minerals, water and air it contains. Soil can also be different in acidity. The composition, characteristics and acidity of soil affect the types of plants that can grow there. This in turn affects the types of other organisms in an ecosystem. Compare and contrast the soil in a grassland and a desert ecosystem. How does the soil affect the organisms in each ecosystem?

Activity 5.4

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Think Deeply How can human activities affect the abiotic and biotic factors in an ecosystem?

Biotic Factors The characteristics of an ecosystem that are caused by living things are called biotic factors. These include the presence and effects of all of the plants, animals, fungi and microorganisms. The types of organisms in an ecosystem is greatly influenced by both the abiotic factors and the biotic factors. Scientists organize the living things in an ecosystem to better understand the interactions between biotic and abiotic factors.

Did You Know? A species is a single type of organism. All species are classified into groups and given a unique name. The midland painted turtle is called Chrysemys marginata. This naming system helps scientists identify and communicate information about species more easily. The midland painted turtle is an organism in a pond ecosystem.

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How can the types of insects in an ecosystem affect the plants and animals that live in the same ecosystem?

Ecosystem Organization An organism is a single individual within a species living in an ecosystem. Scientists may study an organism to find out what it eats, where it lives or how it reproduces. They may study the adaptations that help it survive in the ecosystem. A single midland painted turtle is an example of an organism in a pond ecosystem.

All of the midland painted turtles in an ecosystem form a population.

All of the same species that live, interact and reproduce in the same ecosystem is called a population. Scientists study the ways in which populations interact with each other and the effects of populations on other populations. All of the midland painted turtles interacting and reproducing in a pond ecosystem are an example of a population.

Think Deeply What are some abiotic and biotic factors that could affect the size of a tree frog population in a rainforest ecosystem?

The midland painted turtle feeds on aquatic insects. Changes in the size of the midland painted turtle population can affect the populations of aquatic insects. What effect could changes in the population size of midland painted turtles have on a pond ecosystem?

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Think Deeply Sometimes, people introduce new species into ecosystems. How could this change affect the community?

pond skaters

cattails

All of the populations living and interacting in an ecosystem form a community. The pond community of the midland painted turtle consists of all of the populations of other organisms that live in and around the pond. It includes the populations of water lilies, cattails, insects, frogs and fish. It includes all of the populations of fungi around the pond and the microorganisms in the water and soil. The populations interact in many ways and changes to populations can affect the community as a whole.

freshwater carp

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Scientists study how the increases and decreases in populations affect other populations within the community. As the number of organisms in an animal population increases, there may be decreases in the populations of the organisms it feeds on. Population interactions also occur when animals pollinate flowers and disperse seeds.

Activities 5.5 – 5.7

bullfrogs

What is the difference between a community and an ecosystem?

Try This! Visit a natural ecosystem in your area. Describe the organisms, populations and community that make up the ecosystem.

midland painted turtle

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Energy Flow in Ecosystems A stork gets energy when it eats a frog.

Energy flows between the organisms in an ecosystem. In most cases energy enters the ecosystem when photosynthesizing organisms use the energy in sunlight to make food. Energy is passed to animals when they feed on the organisms. Energy gets passed along again as animals eat other animals. Other organisms within an ecosystem feed on the remains of plants and animals and return nutrients to the soil. A frog gets energy when it eats a grasshopper.

A grasshopper gets energy by eating leaves.

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Producers

Producers are organisms that are able to make their own food through the process of photosynthesis. During photosynthesis, an organism takes in carbon dioxide and water and uses the energy in sunlight to convert them into sugar. The sugar is used by the plant to live, grow and carry out life processes. During photosynthesis, oxygen is also produced. The oxygen is released into the air.

Think Deeply Why is the taking in of carbon dioxide and release of oxygen by producers important to life on Earth?

On land, plants are the main producers. The energy they produce is stored in the plant which can then be passed to other organisms when they feed on plants or plant parts.

Most of the photosynthesis on Earth is done by phytoplankton. Phytoplankton are microscopic photosynthesizing algae that drift around near the surface of the ocean. Either directly or indirectly, phytoplankton are the primary source of energy for ocean life.

Why are photosynthetic organisms called producers?

microscopic phytoplankton

Think Deeply Why do phytoplankton live in the upper layers of the ocean?

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A koala’s diet consists almost entirely of the leaves of eucalyptus trees.

Caterpillar feeding on a leaf.

Consumers The energy that enters an ecosystem when producers photosynthesize is passed on to animals when they feed on the producers. An organism that gets its energy by feeding on other organisms is called a consumer. Consumers that eat only plants or other photosynthesizing organisms are called herbivores. On land, herbivores are animals that feed on plants or the parts of plants. They may eat roots, leaves, fruits or feed on the nectar or pollen produced by flowers.

Krill are marine herbivores that feed mostly on phytoplankton.

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In the ocean, the main herbivores are krill. Krill are small shrimp-like crustaceans that feed mostly on phytoplankton.

How is the food eaten by a lion different from the food eaten by a zebra? Many consumers get the energy they need by eating other animals. These consumers are called carnivores. Lions, snakes and spiders are examples of carnivores.

Lions and snakes are examples of carnivores.

Other consumers have a diet that changes as different food becomes available. They may eat plants at some time of the year and animals at other times of the year. A consumer that eats both plants and other animals is called an omnivore.

Bears are omnivores. They may feed on salmon and other animals for part of the year and grasses and berries at other times.

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woodlice

Mushrooms and other fungi are decomposers.

Decomposers When an organism dies, it leaves behind energy and nutrients. Decomposers are organisms that break down the remains of dead organisms and their wastes. In doing so, they play a vital role in the functioning of ecosystems and life on Earth as a whole. When breaking down decaying matter, decomposers absorb the energy they need to carry out life processes. They also help return nutrients to the soil and help to recycle oxygen, nitrogen and carbon back into the environment. Fungi and bacteria are examples of decomposers. Some animals, such as earthworms and woodlice, also help to breakdown organic matter in ecosystems. These animals are called detritivores.

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Activities 5.8 – 5.9

Food Chains In an ecosystem, there is an energy pathway that can be traced from the producers through to the consumers. This energy pathway is called a food chain. In a food chain, arrows are used to show the direction of energy flow. A food chain can be used to show that almost all of the energy in an ecosystem was once energy from the Sun that was captured by plants during photosynthesis. The energy is passed to herbivorous consumers when they eat plants. It is then passed on to carnivorous secondary and tertiary consumers when they feed on other animals.

This grassland food chain shows that almost all of the energy in the ecosystem can be traced back to the energy in sunlight.

hawk

grass snake

grass rabbit

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Try This! In small groups, list some common organisms in a forest ecosystem. Identify the producers and consumers. Draw simple diagrams to create a forest food chain.

Let’s take a look at a simple desert food chain. The producers in a desert include cacti, grasses and small bushes and shrubs, including brittlebush. Brittlebush use the energy from sunlight to produce energy in the form of sugar during photosynthesis. In this process, energy is transformed from light energy into stored chemical energy in the plant’s tissues. Consumers that eat producers are called primary consumers. One consumer that feeds on brittlebush is the pallid-winged grasshopper. When it consumes the leaves of the brittlebush, energy is transferred from the plant to the grasshopper. A secondary consumer gets its energy by eating primary consumers. In desert ecosystems, grasshopper mice feed on pallid-winged grasshoppers. In doing so, energy passes from the grasshoppers to the mice.

pallid-winged grasshopper (primary consumer)

brittlebush (producer)

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Further up the food chain, energy is passed to tertiary consumers when they feed on secondary consumers. In this case, it is diamondback rattlesnakes feeding on grasshopper mice. At the top of a food chain are the top predators. Top predators are tertiary consumers that have no natural predators. An eagle feeding on snakes is a top predator in a grassland.

red-tailed hawk (top predator)

Think Deeply

AB Activity 5.10

Provide an example of an event that could affect the population of pallid-winged grasshoppers in the desert food chain. How might the other organisms in the food chain be affected?

diamondback rattlesnake (tertiary consumer)

grasshopper mouse (secondary consumer)

Use another ecosystem to create a model to show how almost all of the energy in a food chain can be traced back to the Sun.

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Food Webs In an ecosystem, there is almost always more than one food chain. Primary consumers usually get the energy they need by eating more than one type of plant. Secondary and tertiary consumers also get their energy from more than one type of animal. To more accurately show the different relationships between the organisms in an ecosystem, we can use a food web. A food web is a model used to show the interconnected food chains in an ecosystem. It shows the many paths energy can take as it flows from one level to the next.

Activity 5.11

deer (primary consumer)

grouse (primary consumer)

fungi (decomposer) plants (producers)

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hawk (secondary consumer)

woodpecker (secondary consumer) bear (omnivorous consumer)

snake (secondary consumer)

squirrel (primary consumer)

rabbit (primary consumer)

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Energy Pyramids As energy flows through an ecosystem, most of the energy is used up by the organisms at each level in the food chain. The energy is used to carry out life processes like body repair, respiration, digestion, movement, and in warm-blooded animals, to maintain body warmth. Some energy is also given off as heat. Only about 10 percent of the energy is stored in the tissues of the organisms and is passed on to the organisms in the next level. An energy pyramid is a model that shows how much energy is available at each level in an ecosystem and the number of organisms each level can support.

tertiary consumers

energy pyramid for a desert ecosystem

secondary consumers

primary consumers

producers energy in

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energy passed to next level

energy used or lost

Because less energy is available at each level as you go up a food chain, the number of organisms that can survive decreases too. In a healthy and balanced ecosystem, the number of producers is greater than the number of primary consumers. The number of primary consumers is greater than the number of secondary consumers. Only a small amount of the energy remains to support the top predators. An energy pyramid is a useful tool in determining if an ecosystem is balanced. If the model does not resemble a pyramid shape, it may indicate the ecosystem is unstable, unhealthy or is undergoing change.

Activities 5.12 – 5.13

energy pyramid for an Arctic ecosystem

tertiary consumers

secondary consumers

primary consumers

producers energy in

energy passed to next level

energy used or lost

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Science Words Use the words to complete the sentences. system ecosystem biotic factors abiotic factors organism population

community producer consumer herbivore carnivore

omnivore decomposer food chain food web energy pyramid

1. A is an organism that breaks down the remains of dead organisms and their wastes and feeds on the broken down remains. 2. A consumer that gets the energy it needs by eating other animals is a . 3. A consumer that eats only plants or other photosynthesizing organisms is a . 4. The non-living components in an ecosystem are called 5. The living components of an ecosystem are called

. .

6. An is a system in nature where all of the living and non-living parts function as a whole. 7. A is a group of interacting or interrelated parts that work together to function as a whole. 8. All of the populations living and interacting in an ecosystem form a . 9. An is a single individual within a species living in an ecosystem. 10. A is an organism that is able to make its own food through the process of photosynthesis.

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11. An organism that gets its energy by feeding on other organisms is a . 12. A consumer that eats both plants and other animals is an

13. All of the same species that live, interact and reproduce in the same ecosystem is called a . 14. An is a model that shows how much energy is available at each level in an ecosystem. 15. A is a model used to show the interconnected food chains in an ecosystem. 16. A is a model showing a single energy pathway in an ecosystem.

Review 1. Explain how an ecosystem is an example of a system. 2. Copy and complete the table. Ecosystem

Abiotic Factors

Biotic Factors

Pond Grassland Forest Coral Reef 3. Provide an example where a change in the abiotic factors in a pond ecosystem can affect the biotic factors. 4. Provide an example where a change in one abiotic factor in a pond ecosystem can affect the other abiotic factors.

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5. What role do decomposers play in an ecosystem? 6. Draw a simple labeled diagram to show that almost all of the energy in a grassland ecosystem can be traced back to the energy from the Sun. 7. How is a food chain different from a food web? 8. Label the producer, primary consumer, secondary consumer, tertiary consumer and decomposer.

(b) (a)

(c)

(d)

(e)

9. Draw a simple, labeled energy pyramid for a tropical rainforest ecosystem. 10. Why is only 10 percent of the energy in an ecosystem passed on to the next level in a food chain? 11. What might an energy pyramid that does not have a pyramid-like shape indicate about an ecosystem?

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Next Generation Science Level 6 - Textbook A

Articles inside

Unit 1 - Life on Earth

Unit 2 - Plants