Excellence in Biology Senior Secondary 1 Student's Book by Cambridge International Education

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Biology

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Student’s Book: ISBN - 9781316508824 Teacher’s Guide: ISBN - 9781316508862

• a Scheme of Work to help plan lessons • clear teaching guidelines • answers to exercises, activities and case studies in the Student’s Book • evaluation tools to help assess students’ development of specific skills • a practice examination paper to prepare students for the exit examination they will write at the end of Senior Secondary 3.

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• key words and a glossary and explanations in accessible language to enable understanding and learning of knowledge and skills in biology • local and international content supported by full colour illustrations, diagrams and photographs • a variety of practical activities, exercises and case studies to enable students to apply scientific knowledge and skills • revision questions and summaries for each topic to facilitate revision throughout the book.

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Cambridge Biology Senior Secondary 1 has two components.

Cambridge Excellence in Biology Senior Secondary offers you a first-class print and digital course in biology. The course has been developed in accordance with the 2013 NERDC curriculum and Scheme of Work. It offers students accessible, high quality content to ensure the best foundation for future learning.

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Contributors/Reviewers:

F. Fakeye P. A. Ojajuni J. O. Afolabi

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Dear Teacher Welcome to Cambridge Excellence in Biology! Cambridge University Press understands that education is a top priority for all Nigerians. We are now expanding our global offering to include learning and teaching material for all Nigerian schools that follow the NERDC curriculum. Cambridge Excellence in Biology will give every student in Nigeria the opportunity to benefit from the tradition of excellence that is the hallmark of Cambridge University. We invite you to take advantage of our Nigerian specific, world-class learning, teaching and digital resources, developed by international and Nigerian experts. Cambridge Excellence in Biology has been specifically developed to provide you with a: •• complete •• accessible •• affordable solution to ensure excellent results and to introduce your students to a lifetime of achievement. Cambridge Excellence in Biology offers the following: A Student’s Book, written in clear and easy to understand language to make learning effortless, which is also available in digital format. A print and digital Teacher’s Guide to help you prepare your lessons and save time. We trust that Cambridge Excellence in Biology will lay a solid foundation on the journey towards a bright and successful future!

Aim for Excellence with Cambridge!

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Contents Theme 1: Organisation of life Topic 1:

Recognising living things

Topic 2:

The classification of living things

Topic 3:

The cell

Topic 4:

The cell and its environment

Topic 5:

Some properties and functions of cells

Theme 2: The organisation at work Topic 7:

Tissues and supporting systems

Topic 8:

Nutrition in animals

Theme 3: The organism and its environment Topic 8:

Basic ecological concepts

Topic 9:

A functioning ecosystem

Topic 10: Energy transformation in nature Topic 11: The relevance of Biology to agriculture Topic 12: Micro-organisms around us Topic 13: Micro-organisms in action Topic 14: Towards better health Topic 15: Aquatic habitats â&#x20AC;&#x201C; marine, estuarine and freshwater Topic 16: Terrestrial habitat

Theme 4: Continuity of life Topic 17: Reproduction in unicellular organisms and invertebrates

Glossary

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Topic 2: The classification of living things Performance objectives 2.1 State the characteristic features of the kingdoms and give specific examples of representative organisms.

How scientists classify organisms Scientists estimate that there are more than 2 million different plant and animal species in the world. Amazingly, new species are being discovered all the time. It is important for scientists to use a consistent method to sort these organisms so there is a clear way of grouping them according to shared features or characteristics. Classification systems generally take into account the main features of organisms such as body shape, skeleton type, type of limbs, the number of legs or how the internal organs are arranged. There is a range of other characteristics used to classify organisms. The name given to the classification process is taxonomy. You will find out about a few of these in this topic.

The following criteria or questions are used to classify these organisms into the separate kingdoms listed above: • Are they unicellular, multicellular or colonial (living in clusters or groups)? • Is a nucleus present or absent in the cell and are there organelles (such as chloroplasts)? • What does the cell wall consist of ? • Is the organism mobile? • How does it feed (is it autotrophic/ heterotrophic)? • How does it reproduce (sexual or asexual reproduction)? We will now look at each of the five kingdoms in greater detail. We will also investigate the different characteristics in each and will look at examples of representative organisms in each kingdom.

The difference between Eukaryotes and Prokaryotes

The five kingdoms

Eukaryotes are cells with a nucleus. Their DNA lies within this nucleus and they contain complex organelles. They include fungi, plants and animals, as well as singlecelled organisms called protists. Prokaryotes are cells without a nucleus and their DNA lies freely inside the cytoplasm. Bacteria fall into this group.

In Biology, we divide organisms into very large groups called kingdoms. The five kingdoms are as follows: 1. Monera (bacteria) 2. Protista 3. Fungi 4. Plantae 5. Animalia

Topic 2 The classification of living things

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Kingdom Monera (bacteria)

Kingdom Protista

• Bacteria are microscopic and single-celled

Protists are a diverse group of microscopic organisms (that are eukaryotic). There are about 64 000 species and they include unicellular protozoans, algae (unicellular, colonial and multi-cellular) and slime moulds. • Protists are different from simpler bacteria in that they contain complex organelles such as chloroplasts and mitochondria. • They move using flagella or cilia. • They respire aerobically and reproduce sexually producing male and female gametes. • Protists have no tissues or organs. • They exist in symbiotic, parasitic and free-living forms. • Protists are either phototrophs (able to photosynthesise) or heterotrophs (able to engulf and absorb their food). • They form the basis of most freshwater and marine ecosystems. • Many of the diseases that affect agriculture, humans and animals are caused by protists.

organisms.

• They vary considerably in shape and size • • • • •

•

and can be round, spiral, chained, branched or rod-shaped. Bacterial cells are what we call prokaryotic. This means that they do not have a nucleus or complex organelles. Bacteria reproduce by a process of binary fission which is a form of asexual reproduction. Bacteria are a vital group of organisms and play a very important role in nutrient cycling and decomposition. They also help to maintain atmospheric levels of carbon dioxide and oxygen. Harmful bacteria can cause diseases in plants which can damage crops. In animals and humans, bacteria can cause diseases such as cholera, leprosy and pneumonia. Some are mobile. Some are not.

bacillus – rod

coccus – sphere

Cocci in various arrangements

pair

Rods of various shape and arrangement

short rod group of four

long rod

curved rod

group of eight

chain

chain branched

irregular group

spiral

Figure 2.1 Examples of the different shapes of bacteria

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Theme 1 Organisation of life

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FREE-LIVING PROTOZOANS

Euglena ×150

Amoeba ×60

Paramecium ×150

Vorticella ×100

PARASITIC PROTOZOANS

Plasmodium ×1 000

Trypanosoma ×1 500

FRESH WATER ALGAE

Scenedesmus

Chlamydomonas

Volvox

Ulothrix Diatoms

Gonium

MARINE ALGAE

Gonyaulax (causes red tide)

Amphiroa (red alga)

Ulva (sea lettuce)

Codium (green alga)

Eklonia (kelp)

Figure 2.2 Examples of different body shapes and forms found in protists

Topic 2 The classification of living things

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A Amoeba sp. cytoplasm

contractile vacuole

food vacuole

pseudopods food particle being ingested by pseudopods (phagocytosis)

nucleus

direction of movement B Euglena sp. flagellum

anterior end stigma (eye spot) reservoir

chloroplasts

nucleus contractile vacuole

posterior end Figure 2.3 Examples of protists – Euglenia sp. and Amoeba sp.

Types of protists Protozoa (animal-like protists) • Protozoa are animal-like protists. They cause many human diseases such as malaria, sleeping sickness and vaginitis. They are mainly single-celled protists that are about 0.01−0.5 mm in size and are only visible with a microscope. • They feed by ingesting their food with mouth-like structures or structures called pseudopodia that engulf their prey. • Their prey items usually include bacteria or other single-celled organisms. • Amoeba live in freshwater and are a form of the division rhizopodia. They are also single-celled organisms with pseudopodia. • One form (entamoeba histolytica) causes dysentery in humans. • Another form of rhizopoda is plasmodium vivax, which causes malaria. • Paramecium is an example of the group of the division of protists called ciliophora. These are solitary organisms that live in fresh water. 16

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• They move using cilia. Ciliophora can be divided into flagellates (those with flagella), e.g. Euglena, amoeboids (amoeba) and ciliates (those with cilia), e.g Paramecium.

Algae (plant-like protists) • These are photosynthesising protists. They mostly contain chlorophyll. • Algae are found on land and in the water. Phytoplankton are found in the ocean and are a vital part of the ocean food chain. • Green algae, also known as chlorophyta, are found in freshwater and ocean environments. They exist in a variety of forms such as chlamydomonas volvox and spirogyra. • Brown and red algae also exist. Fungus-like protists • This group includes slime moulds and water moulds. • Many of these are decomposers and live in water or in soil.

Activity 2.1 Examine amoeba and chlamydomonas You will need: • a glass container or test tube • a light microscope • a glass slide/slip to view samples under the light microscope • a sample of ditch water or water from a stagnant pond • paper and a pencil Method: 1. With the help of your teacher, you will identify a source of ditch or pond water and collect it in a glass jar or test tube. 2. Your teacher will help you to prepare a slide with a sample of pond/ditch water. 3. Look at the sample under the microscope. What do you see?

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4. Draw the organisms you observe. 5. What kingdom do you think they

belong to? 6. List some of the characteristics of these organisms.

Kingdom Fungi Mushrooms, toadstools, moulds and yeasts are examples of organisms in this kingdom. They lack chlorophyll so they feed heterotrophically. This means they must absorb organic compounds from decaying organic matter, the soil, or from the dead bodies of other organisms. The main characteristics of fungi are: • They are made up of eukaryotic cells. • Their cell walls contain cellulose. • They are heterotrophs (with many being saprophytes or parasites). • They reproduce sexually by dispersing spores (using wind, water or ingestion by animals) as well as asexually. • Most respire aerobically, but some yeasts are anaerobic and respire anaerobically.

• Most of these organisms are able to •

photosynthesise as they contain the pigment chlorophyll. They have the capacity to store starch as an energy reserve.

The kingdom can be grouped in a number of ways, but the most common way of dividing or classifying it is to look at: • their reproductive characteristics • their tissue structure (non-vascular or vascular) • their seed structure (naked, covered seeds or spores) • their size – mosses, ferns, shrubs, trees or herbs. The kingdom has three main sub-divisions: 1. Non-vascular plants: mosses (bryophytes) and liverworts (hepatophytes) 2. Vascular plants (without seeds, but with spores): ferns, horsetails and club mosses 3. Vascular plants (with seeds): gymnosperms and angiosperms. A

Types of fungi There are a few divisions of fungi and these include Basidiomycota, Ascomycota and Zygomycota. Basidiomycota includes mushrooms, puffballs and rusts.

Kingdom Plantae

A: Non-vascular

The plant kingdom includes flowering plants, mosses, conifers, horsetails and liverworts. There are approximately 300 000 species and most of these are flowering plants. • These organisms are multicellular and are made up of eukaryotic cells. • Their cell walls are made of cellulose. • Most of them have roots, stems and leaves.

C: Vascular (with seeds)

Figure 2.4 Examples of the three main divisions in the plant kingdom

Non-vascular plants • Mosses are non-vascular. • They are usually a vital foundation plant in forest ecosystems, helping to prevent soil loss through erosion.

Topic 2 The classification of living things

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B: Vascular (without seeds)

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• They reproduce by means of spores and • •

not by means of seeds. They rarely produce flowers, and are found growing on the ground, on rocks, and on other plants. The approximately 24 000 bryophyte species are grouped into the divisions Mosses (Bryophyta), Liverworts (Hepatophyta), and Hornworts (Anthocerotophyta).

Vascular plants with spores • Ferns and other species in this division have • • •

a vascular system (with well-developed tissues responsible for water transport). They reproduce from spores as opposed to seeds. Ferns are the most plentiful division in this group. (There are 2 000 species.). Other divisions include club mosses, horsetails and whisk ferns.

• Flowering dicots include trees, shrubs, flowers and vines. Most fruit and vegetables are from this class.

Kingdom Animalia The animal kingdom is divided into vertebrates (animals with backbones) and invertebrates (animals without backbones). It is estimated that there are between 20 and 50 million species of animals, with the largest group being insects. Figure 2.5 shows how we classify organisms into sub-categories within a kingdom. See also Table 2.1 on the following page: Domain

Kingdom

Vascular plants with seeds The two categories of vascular plants with seeds are gymnosperms and angiosperms. Gymnosperms include conifers, cycads, pines, firs and cedars. • They are evergreens. • Gymnosperms reproduce from seeds. • The seeds (usually in cone-like structures) are ‘naked’. • They often have needle-like leaves. Angiosperms include monocotyledons (monocots) and dicotyledons (dicots). • The majority of plants (around 230 000) belong to this category. • They include trees, shrubs, vines, flowers, fruits, vegetables, and legumes. • Their seeds grow inside an ovary, which is embedded in a flower or fruit. • Flowering monocots include orchids, palms and grasses. They have parallel leaf veins and do not produce wood.

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Eukarya

Animalia

Phylum

Chordata

Class

Mammalia

Carnivora

Order

Family

Genus

Species

Felidae

Panthera

Panthera pardus

Figure 2.5 The different sub-categories in the classification of animals

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Table 2.1 summarises the chief characteristics of some of the main phyla in this kingdom. Table 2.1 The characteristics of the main phyla Phylum

Examples

Characteristics

Profiera

sponges

• no tissues or organs • contain a few specialised cells, which perform various functions their bodies are random/asymmetrical adults are sessile, filter feeders tiny pores all over body for water flow collagen important in their structure

Cnidaria

jellyfish, anemones

Echinodermata

starfish, sea urchins, sand dollars, brittle stars

• • • • • soft bodied, jelly-like stinging tentacles • two-layered bodies with radial symmetry • polyps (fixed) and medusae (free swimming) • reproduction asexual • spiny skeleton with several arms reaching from central point internal skeleton water vascular system

• • • body divided into segments, separated by internal walls • bristles are attached to each segment • similar nervous system to arthropods • head includes tentacles, palps and eyespots • approximately 900 000 species known in this phyla • jointed legs • tough exoskeleton made of chitin • segmented body with a head, thorax, abdomen

Annelida

earthworms, leeches

Arthopoda

shrimps, spiders, crabs, ticks

Platyhelminthes

planarians, tapeworms

• unsegmented, flattened body • bilateral symmetry • they have a ‘head end’ to the body • gastrovascular cavity with a pharynx

Mollusca

clams, mussels, snails, squid, octopus

Chordata

fish, birds, amphibians and mammals

• soft-bodied organisms • internal or external shell • foot, mantle, shell, visceral mass • aquatic form has lungs • use of cillia for feeding, respiration and digestion • dorsal, hollow, nerve cord (spinal cord) • post-anal tail (apes and frogs have no tail as adults) • pharyngeal pouches (gill slits) • found in most places (oceans, rivers, forests and mountains)

Nematoda

roundworms

• tiny slender, unsegmented, tapering ended worms free living and parasitic

• found in every environment (50 species parasitise humans)

Topic 2 The classification of living things

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Activity 2.2 Answer questions

1. Which of the following is in the correct

4. 5. 6. 7.

8. 9.

order of classification in order of increasing relatedness? A phylum, kingdom, order, species, family, class, genus, domain B domain, species, order, family, phylum, class, genus, kingdom C species, order, class, family, domain, genus, kingdom D domain, kingdom, phylum, class, order, family, genus, species The name given to the science of classification is: A relatedness B genetics C grouping D taxonomy The key feature that distinguishes eukaryotes from prokaryotes is their: A cell wall B mitochondria C chloroplasts D nucleus Name one beneficial bacteria and two harmful bacteria. Name four characteristics of protists. Protozoa are -like protists -like protists. and algae are Explain the difference between gymnosperms and angiosperms and give examples of each. What is the most common way to classify or group organisms in the plant kingdom? List three characteristics of the kingdom fungi and indicate their value in ecosystem functioning.

10. Look at the photographs and answer

the questions that follow:

Summary • Taxonomy is the classification of organisms. • Organisms are grouped into domain,

a) Identify the phylum for organisms

A to E. b) List three characteristics of each.

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•

kingdom, phyla, class, order, family, genus and species. The five kingdoms are: Bacteria, Protista, Fungi, Plantae and Animalia.

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Key words

How are you doing? Use the Revision questions to check if there is anything you do not understand. Ask your teacher to explain.

Do you know the meanings of these terms? If not, look up these words in the glossary at the back of the book. classification, eukaryotes, kingdoms, prokaryotes and taxonomy

Revision questions 1. We classify organisms into Bacteria,

Protista, Fungi, Plantae and Animalia. What are the six criteria or questions we use to do so? 2. Study the diagram and answer the questions that follow: a) Name the Kingdom illustrated here. b) What is common to all these organisms and defines the phylum? c) The fact that they are ____________ defines their class. d) What do all of them feed on (this defines their order)? e) What is the English word derived from the latin word Felidae?

Family

Genus

Specific epithet

Catus

Kingdom

Animalia

Phylum

Chordata

Class

Mammalia

Order

Carnivora

Canidae

Felidae

Felis

Panthera

pardalus

(Hint: look at the three animals on the purple blocks for a clue). f) What do you think the word Ursus means? g) What do you think the word lupus means? 3. Eukaryotes and prokaryotes are different types of cells. a) State the single most important difference between eukaryotes and prokaryotes. b) Which large and important kingdom(s) represent prokaryotes? 4. List three characteristics of the Kingdom Fungi.

pardus

Ursidae

Canis

familiaris

Ursus

lupus

Topic 2â&#x20AC;&#x201A; The classification of living things

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arctos

horribilis

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Topic 8: Nutrition in animals Performance objectives 8.1 Understand different food substances. 8.2 Understand the different classes of food. 8.3 Understand the importance of a balanced diet. 8.4 Understand and name the digestive enzymes and their characteristics, classes and functions. 8.5 Understand the different modes of nutrition in different organisms.

Food substances

Fat provides a layer of insulation under the skin for warmth. Fats are also found in the myelin sheaths that surround nerve cells. Fats in the diet also allow the body to use fat-soluble vitamins.

The foods we eat are made up of: • fats and oils • proteins • carbohydrates • minerals • vitamins. All of these are necessary for a balanced diet in mammals.

Fats Fats and oils are lipids. A fat is a lipid that is a solid at room temperature. An oil is a lipid that is liquid at room temperature. Fats and oils are found in these foods: • meat • butter and margarine • olives • acovados • cheese • milk and yogurt. Fats provide energy. One gram of a lipid provides more than twice the amount of energy than does one gram of carbohydrate. But, because the biological processes that are needed to release energy from fats in the cell are long and complicated, cells use carbohydrates for energy more easily than they use fats.

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Figure 8.1 Foods that contain fats

Activity 8.1 Test for the presence of fats and oils (the translucent spot test) What you need: • a small amount of oil • ethanol • test tubes • filter paper A drop of oil-ethanol solution

filter paper

B drop of ethanol solution only

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Method: 1. Put two drops of oil into a test tube. Add 5 ml of ethanol to the oil. Shake thoroughly until the oil dissolves. 2. Put a drop of the mixture on filter paper A. Draw a ring around the position of the drop with a pencil. 3. As a control, put a drop of ethanol on filter paper B and draw a ring around the position of the drop with a pencil. 4. Allow the filter paper to dry and compare filter paper A and B.

Activity 8.2 Test for the presence of proteins (Millon’s reagent test) What you need: • egg white • water • test tubes • Millon’s reagent • a water bath • a heat source A

Answer these questions: 1. Why is the stain left on filter paper A called a ‘translucent’ stain? 2. What other oil solvent could be used instead of ethanol?

Proteins Proteins are found in foods such as meat, eggs, milk, cheese and beans.

Figure 8.2 Foods that contain proteins

Proteins are part of the building materials of all cell membranes, chromosomes, cytoplasm and cell organelles. All enzymes and some hormones are made up of proteins. Proteins are also necessary for the immune system to work properly. Proteins are seldom used for energy, except in extreme malnutrition when the body has used up all carbohydrate and fat reserves.

2 ml egg white + 2 drops Millon’s reagent + heat

Method: 1. Pour an equal quantity of egg white and water into test tube A. Mix thoroughly. 2. Add 1 ml of Millon’s reagent to the test tube. (Take care because it contains mercury and is poisonous.) 3. Heat the test tube in a water bath containing boiling water. Note the colour of the contents of the test tube. 4. As a control, repeat the procedure but use 2 ml of a glucose solution instead of using egg white (test tube B). Result: You will see that the solution in test tube A becomes a brick-red precipitate (positive result) and no colour change occurs in test tube B (negative result).

Topic 8 Nutrition in animals

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2 ml glucose + 2 drops Millon’s reagent + heat

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Activity 8.3 Carry out an alternative test for proteins (the Biuret test) What you need: • dilute solutions of sodium hydroxide and potassium hydroxide (both dilute) • test tubes • copper sulphate • egg white A 2 ml egg white + 10 ml NaOH/KOH + 2 drops CuSO4

B 2 ml glucose + 10 ml NaOH/KOH + 2 drops CuSO4

Method: 1. Pour about 10 ml dilute sodium hydroxide (NaOH) or dilute potassium hydroxide (KOH) solution into a test tube. (Be careful: both are corrosive.) 2. Add two drops of copper sulphate (CuSO4) solution. The solution is blue. 3. Add 2 ml of egg white to the test tube. Note: Do not heat the solution. 4. As a control, repeat the procedure but use 2 ml of glucose solution instead of egg white (test tube B). Answer these questions: 1. Name the protein found in egg-white. 2. Name one other food stuff that contains protein. Result: The solution in test tube A becomes violet (positive result) indicating that the solution contains protein. No colour change occurs in test tube B (negative result).

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Carbohydrates Carbohydrates are found in grains and the foods such as bread, cereals, potatoes, rice, yams and sugars that are made from grains. Carbohydrates are an important source of energy, especially sucrose and glucose. Carbohydrates store energy, for example, starch in plants and glycogen in humans. Plant cell walls are made of carbohydrates.

Activity 8.4 Test for the presence of a carbohydrate (glucose) What you need: • Fehlings A Solution • Fehlings B Solution • (You can use Benedict’s Solution instead of Fehlings) • glucose • test tubes • a source of heat • chalk A

reducing sugar (glucose) + Fehling's solution + heat

crushed chalk + Fehling's solution + heat

1. Mix 2 ml of Fehlings A Solution and

2 ml of Fehlings B Solution in test tube A (4 ml of Benedict’s Solution can be used instead of Fehlings Solution). This mixture is a deep blue colour. 2. Add 2 ml of glucose solution to test tube A containing Fehlings A Solution and Fehlings B Solution or Benedict’s Solution. Heat the mixture in a water bath containing boiling water.

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3. As a control, repeat the procedure but

iodine solution

use crushed chalk instead of glucose in test tube B. Answer these questions: 1. Why is the mixture in test tubes A and B heated in a water bath? 2. Name three other sugars which would give the same result when heated in a water bath with Fehlings A solution and Fehlings B solution or Benedict’s solution. Result: The solution containing glucose (test tube A) turns yellow and then orange (positive result). The crushed chalk solution (test tube B) remains blue (negative result). This shows that glucose is a carbohydrate because when it is added to Fehling’s Solution, the solution turns yellow and then orange. If you are given an unknown sample of food and asked whether glucose is present, then you have to apply the Fehlings or Benedict’s test to the sample, that is, you use the food sample instead of glucose.

Activity 8.5 Test for the presence of starch You will need: • starch solution • iodine solution • test tubes • glucose

starch solution

non-starch solution

Answer these questions: 1. Name two foods that contain starch – test them using iodine. 2. Give an example of a substance you would have used in B. 3. How would you test a solution to see if it contained iodine? Result: A substance that turns blue-black in the presence of iodine contains starch (positive result) and a substance that takes on the colour of iodine (brown) does not contain starch (negative result).

Activity 8.6 Classify different food Your teacher will provide you with samples of different kinds of food such as yam, garri, butter, cooking oil, salt, fish, prawns, pepper, cowpea, crab and onions. 1. In groups classify the different foods into fats, oils, proteins or carbohydrates. Some foods contain more than one food type. 2. Make a table with the headings: fats, oils, proteins and carbohydrates. List the foods under the correct heading.

1. Add 3 ml of the starch solution to test

Minerals

tube A. 2. Add two drops of iodine solution to test tube A. The solution turns blue-black. 3. As a control, repeat the procedure on glucose in test tube B. The solution takes on the colour of iodine (it remains brown).

Minerals that are necessary in the diet are divided into groups. Macro-elements, which are needed in large quantities, include nitrogen, sodium and calcium. Micro-elements, which are needed in small quantities, include iodine and iron.

Topic 8 Nutrition in animals

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Table 8.1 shows the function of the more important minerals in humans. Table 8.1â&#x20AC;&#x201A; The functions of minerals Mineral

Function

Deficiency diseases

Nitrogen (N)

Essential for the synthesis of amino acids that form protein; Forms part of the nucleotides of DNA and RNA.

Retarded growth; Kwashiorkor in young children

Sulphur (S)

Present in most proteins, co-enzymes and the hormone insulin.

Poor growth

Magnesium (Mg)

Essential component of chlorophyll molecules; Plays a part in muscular contractions and the functioning of the nervous system; Activates enzymes.

Poor growth

Phosphorus (P)

Important for bones and teeth formation; Part of the energy carrier ATP; Important component of DNA and RNA; Found in phospholipids of cell membranes.

Rickets, malfunctioning of muscle and nerves

Sodium (Na)

Maintains osmotic and acid-base balance of body fluids; Necessary for osmoregulation in the kidneys; Necessary for the secretion of HCl in the stomach; Necessary for functioning of nerves and muscles.

Hyponatraemia leading to nausea, vomiting, lethargy, coma and death

Calcium (Ca)

Essential for the structure of bone and teeth; Calcium ions needed for blood clotting; Plays a part in cell membrane permeability.

Rickets, blood clotting delay

Iron (Fe)

Part of haemoglobin in red blood cells (deficiency results in anaemia); Component of electron carriers in respiration.

Anaemia

Iodine (I)

Constituent of the hormone thyroxin that is secreted by the thyroid gland (deficiency causes goitre).

In humans, cretinism in children, goitre in adults

Potassium (K)

Necessary for functioning of nerves and muscles.

Malfunctioning of muscle and nerves, heart irregularities

Vitamins Vitamins are organic compounds that are essential for the maintenance of many metabolic activities. Some are water soluble, while others are soluble in fat. Fat soluble vitamins (A, D, E and K) are absorbed with glycerol and fatty acids into the

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lacteals. Fat soluble vitamins can be stored in the bodies of plants and animals. However, the water soluble vitamins (B and C) cannot be stored and must be renewed daily. If we do not take in vitamins in our diet, we may get what is called a vitamin deficiency disease.

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Table 8.2 shows the source and functions of the more important vitamins needed by our

body. It also shows the deficiency diseases that are caused by a lack of these vitamins.

Table 8.2 The source and function of vitamins Vitamin

Source

Function

Deficiency disease

A (retinol)

carrots yellow fruit milk dairy products liver fresh green vegetables

Essential for the correct functioning of the eye; Improves the eye’s adjustment to darkness.

Night-blindness-poor vision in dim light; Xerophthalmia – cornea becomes dry and develops small sores.

D (calciferol)

animal fats and oils dairy products (milk, cream, butter, cheese) egg yolk fish liver oils

Plays a role in bone growth; Increases calcium and phosphorus absorption by the small intestine and deposition of these salts in bone.

Rickets – bone deformity in children; Osteomalacia – in adults, bones become soft and fractures may occur.

E (tocopherol)

green, leafy vegetables, e.g. spinach, lettuce eggs whole wheat bread

Acts as an anti-oxidant – prevents cell membrane damage.

Causes neuro-muscular disorders, e.g. nerve degeneration in the hands and feet; Deficiency is rare.

green leafy vegetables, e.g. spinach, lettuce; made by intestinal bacteria

Needed for blood clotting.

Failure of blood to clot; Bleeding gums and easy bruising of skin.

B3 (niacin)

whole grains of cereal fish liver lean meat

Part of co-enzymes used in cellular respiration.

Pellagra – weakness, loss of weight, diarhoea, irritability.

C (ascorbic acid)

Citrus fruit (oranges, lemons) fresh vegetables guavas tomatoes

Maintains intercellular substance in bone, cartilage and dentine; Formation of connective tissues, e.g. collagen.

Scurvy – bleeding under skin and bleeding gums; Poor healing of wounds, degeneration of skin, teeth and blood vessels.

A balanced diet What is a balanced diet? Humans and other mammals rely on food produced from plants and animals. A balanced diet includes all the energy nutrients (carbohydrates, proteins and lipids), vitamins, minerals, water and fibre required to maintain good health.

Figure 8.3 A food guide pyramid

Topic 8 Nutrition in animals

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The energy released from foods is expressed in kilojoules. The amount of energy required by individuals differs in terms of the age, gender, activity and the kind of work a person does. Table 8.3 shows this difference. Table 8.3 The energy requirements of different groups Child/adult

Type of activity/ Amount of energy occupation per day (kJ)

2-year old

5 000

5-year old

7 000

Child 8-year old

8 000

11-year old

9 000

13-year old

10 000

Woman Man Woman Man Active housewife

Basic metabolic rate − sleeping Desk-bound job Active job

6 000

3. Draw a pie chart to show the relative

proportions of protein, carbohydrate, fats and fibre in this 100 bowl of cereal.

Malnutrition A person may get malnutrition if their diet is not balanced or if the digestive system malfunctions. Two common forms of malnutrition are kwashiorkor and marasmus. Kwashiorkor is the result of a high intake of carbohydrate with too little protein. Marasmus is a lack of foods in all food groups. These two disorders are usually seen in children in resource-poor areas.

7 000 8 000 9 000

Digestive enzymes

12 500

Ingredients

Nutritional information (Values per 100 g)

whole rolled oats, roasted wheat flakes, cane syrup, brown sugar, vegetable oil, sun-dried raisins

Energy

2 000 kJ

Protein

12,5 g

Carbohydrates

50 g

An enzyme is a protein molecule that acts as a biological catalyst because it speeds up biochemical reactions. Enzymes are specific to the substrates that they act on. For example, all enzymes that act on proteins are called proteases. So proteases will not be able to break down carbohydrates. In addition, they work best in particular environmental conditions such as pH and temperature. Table 8.4 summarises the broad groups of enzymes, where they are produced, on what substrate they work, the type of pH they prefer and the end products of their action.

Fats

12,5 g

Table 8.4 A summary of the groups of enzymes

Fibre

25 g

Cholesterol

0 mg

Shopkeeper Labourer (man)

Very active job

14 000 20 000

Activity 8.7 Study the nutritional composition of foods The following information appears on the package of a brand of cereal eaten by a young boy.

Study it and then answer these questions. 1. State two reasons why the boy needs each of the following nutrients: a) protein b) fibre 2. The total energy value of 100 g cereal is 2 000 kJ. The boy requires 5 500 kJ of energy per day. How much cereal does he need to eat to get this? Show all calculations. 28

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Group of enzymes

Carbohydrases

Proteases

Lipases

Where they are produced

mouth, small intestine, pancreas

stomach, small intestine, pancreas

small intestine

Substrate

carbohydrates

proteins

lipids

Preferred pH

alkaline – neutral

acid

neutral

End products

glucose

amino acids

fatty acids and glycerol

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Activity 8.8 Break down starch You will need: • bread or crackers • something to break up the bread or cracker, such as a pestle and mortar • test tubes and dropping pipettes • iodine Method: 1. Break up a small piece of bread or cracker with a knife in a pestal and mortar. Mix it with a little water. This is your sample of cooked starch. 2. Divide this sample equally between two test tubes. 3. Add your own saliva to one test tube and leave it for five minutes. 4. The second test tube is the control. 5. Use a dropping pipette to take a small sample from each test tube and test it with a few drops of iodine. 6. Record your results. Result: Starch is broken down by the digestive enzyme in your saliva, which is called salivary amylase or ptyalin. The action of enzymes is affected by pH and temperature. Enzymes work best at the pH and temperature that is found in living organisms. The next two activities demonstrate this.

Activity 8.9 Observe the effect of pH on salivary amylase You will need: • bread or crackers • test tubes and dropping pipettes • hydrochloric acid, sodium hydroxide, iodine

Method: 1. Prepare a sample of cooked starch as you did in the previous activity. 2. Divide your sample equally between three test tubes. 3. Add saliva from your mouth to each test tube. a) Add dilute hydrochloric acid to the first test tube. b) Add dilute sodium hydroxide solution to the second test tube. c) The third test tube is neutral. 4. Leave the test tubes for five minutes. Use a dropping pipette to take out a little of the solution from each test tube. Test the solution with iodine solution to see if it contains starch. Answer the following questions: 1. What happened in the acid conditions? 2. What happened in the alkaline conditions? 3. What happened in neutral conditions? 4. Of the three conditions, in which did the salivary amylase work best? Result: Salivary amylase works best in the slightly alkaline conditions of the mouth. It does not work well in very acid or alkaline conditions.

Activity 8.10 Observe the effect of temperature on salivary amylase You will need: • bread or crackers • something to break up the bread or cracker, such as a pestle and mortar • test tubes • dropping pipettes • spotting tiles • ice and iodine • a source of heat such as a Bunsen burner

Topic 8 Nutrition in animals

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Method: 1. Prepare a sample of cooked starch. 2. Divide your sample equally between four test tubes. a) Add two drops of saliva to the first test tube and boil the contents for three minutes. b) Put the second test tube into a beaker containing ice, or put it in the fridge. c) Put the third test tube into a beaker containing water at room temperature. d) Put the fourth test tube into a beaker containing water at about 37ºC (body temperature). 3. Add two drops of saliva to test tubes B to D. Note the time. 4. At 1-minute intervals, use a dropping pipette to take out a little solution from each test tube. Test it with iodine solution on a spotting tile. Answer the following questions: 1. What happened when the enzyme was boiled? 2. What happened in the very cold conditions? 3. What happened at room temperature? 4. What happened at body temperature? 5. At which temperature did the salivary amylase work most quickly to break down the starch? What is the advantage of this? 6. Describe the way in which temperature affects the action of the enzyme.

Summary • Our food is made up of fats, oils, proteins, •

carbohydrates, minerals and vitamins. Fats provide energy and insulation; proteins are the building blocks for tissues; carbohydrates provide energy; minerals

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are necessary for many body functions and vitamins are organic compounds that are essential for the maintenance of many metabolic activities in the body. A balanced diet is one that has all these different food in the correct proportions. Digestive enzymes act on different components of foods to break them down into molecules to be used by the body.

• •

How are you doing? Use the Revision questions to check if there is anything you do not understand. Ask your teacher to explain.

Key words Do you know the meanings of these terms? If not, look up these words in the glossary at the back of the book. Carbohydrates, enzymes, fats and oils, minerals, proteins, vitamins.

Revision questions 1. 2. 3. 4.

Why are nutrients important? What is the role of fats in the diet? What is the role of proteins in the diet? Why is calcium an important mineral in the diet? 5. What deficiency disease occurs if there is not enough iron in the diet? 6. What deficiency disease occurs if there is not enough vitamin D and calcium in the diet? 7. Name two common forms of malnutrition and list the features of each. 8. What is an enzyme? 9. What type of nutrition do green plants show? 10. What is chemosynthesis?

Theme 2 Organisms at work

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Glossary abstinence – a method of contraception in which the couple do not have sexual intercourse, 100% effective adaptation – in evolutionary biology, a feature that is common in a population because it provides some improved function adaptive radiation – the process in which organisms diversify rapidly into a multitude of new forms, particularly when a change in the environment makes new resources available, creates new challenges or opens new environmental niches allele – a particular form of a gene which usually occurs in pairs, one of each homologous chromosome in a diploid cell nucleus allelopathy – a chemical process used by plants that helps prevents other plants from germinating or growing too close to the next plant, overcrowding it amnion – the embryonic membrane that secretes the amniotic fluid, which is the fluid in which the embryo is supported during development ampullae – the base of the semi-circular canals of the ear which are enlarged into hollow, round areas analogous structures – structures that are found in different species that look the same or have the same function, but which did not evolve from a common ancestor, for example wings in birds and bats androecium – male part of a flower autonomic nervous system – a part of the nervous system made up of the sympathetic and the parasympathetic nervous systems bilharzia – also called schistosomiasis, caused by parasitic flatworms that burrow through the skin when swimming in contaminated water, where there is no proper sanitation biological evolution – the genetic changes that take place over time and lead to new species of organisms blastocyst – the early stage of an embryo when it is made up of a hollow ball of cells, the next stage from the morula blood group – in humans there are four blood groups, A, AB, B and O, these are the ABO blood groups,there are other also many other types of blood groups in humans, such as Rhesus grouping and the Kell system blood typing – humans can be typed into their different blood groups in the ABO and Rhesus systems using tests that distinguish which person is which group, used before a blood transfusion brain – the enlarged top (anterior) part of the spinal cord, made up of the cerebrum, cerebellum, midbrain and hypothallamus

camouflage – a disguise in the form of either colour or shape, that allows an organism to blend in with its environment to avoid predators central nervous system – that portion of the nervous system that is made up of the brain and the spinal cord cerebellum – the second largest part of the brain, which controls the co-ordination of voluntary muscular movement, balance, muscle tone and equilibrium cerebrum – the largest part of the brain that controls all voluntary actions, contains centres of vision, taste, hearing, smell and touch and contains the areas where higher functions lie chemoreceptor – a receptor that senses chemical stimulus, such as the tongue choroid – the layer of the eye that contains the blood tissue and connective tissue, found between the retina and the sclera, supplies food and oxygen to the eye chromosome – a coiled structure that is found in the nucleus of cells that contains DNA and basic proteins cirrhosis – the scarring of liver tissue that results from excess alcohol and some other toxin ingestion climax community – a stable, self-perpetuating set of organisms that experiences very little fluctuation with regards to species composition over a long period of time comparative anatomy – the study of similarities and differences in the anatomy of different species, to show relationships during evolution comparative embryology – a branch of embryology that compares and contrasts embyros of different species to look at evolutionary relationships conditioned reflex – a reflex action in response to a stimulus that has been repeated several times, such a salivation by a dog in response to a bell that marks meal times condom – a barrier method of contraception, a sheath that is placed over the erect penis to prevent sperm from entering the vagina and so the Fallopian tubes conjunctiva – the tissue that lines the inside of the eyelids and covers the sclera (white part of the eye) connector neurons – the neurons that link sensory neurons to motor neurons via synapses continuous variation – the smooth gradation in the differences between individuals in a population, for example variations in height contraceptive implant – an implant under the skin that contains hormones that are slowly released over time that prevent ovulation, which lasts for varying lengths of time and must be replaced when no longer effective

Glossary

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contraceptive injection – an injection that contains a hormone that prevents ovulation for a period of two to three months, depending on the formulation, needs to be repeated every two to three months contraceptive patch – a patch that contains hormones that prevent ovulation that sticks to the skin and releases hormone over time that prevent ovulation, which must be replaced when no longer effective converging lens – a lens for people who are longsighted that allows them to see close objects, bends light rays inwards to focus on the retina cornified layer – the outermost layer of the epidermis is also called the horny layer and it is made up of dead cells courtship – a type of behaviour used to select partners for reproduction courtship colours – colours that may only appear in a particular species during the breeding season that form part of courtship displays, usually in males only Darwin – Charles Darwin, an English naturalist, the ‘father of evolution’, who published On the origin of species by means of natural selection and who is responsible for the modern theory of evolution deoxyribonucleic acid (DNA) – a nucleic acid found in the chromosomes of almost all organisms and which is the primary genetic material dermis – the name given to the connective tissue layer found below the epidermis of the skin; contains nerve endings, sebaceous and sweat glands as well as blood vessels diabetes mellitus – a disease of insulin production and glucose metabolism, split into type 1 diabetes and type 2 diabetes diaphragm – a barrier method of contraception, a diaphragm that is placed high up in the vagina, preventing sperm from getting through the cervix and into the Fallopian tubes dihybrid cross – a dihybrid cross is a cross made to study the inheritance of two traits (instead of one) at the same time discontinuous variation – a form of variation where organisms either have or do not have a particular characteristic, for example male or female display – ritual displays used by different species of animals during the courtship process diverging lens – a lens for correcting short sight, bends light rays outwards to focus on the retina DNA profile – a technique used to identify individuals by characteristics of their DNA ear drum/tympanic membrane – the membrane that separates the middle ear and outer ear and which vibrates in response to sound waves, which are transmitted by the ear ossicles to the oval window

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ecological succession – the process of change in which a set of natural communities are established and then replaced over a period of time, looks at the structure of a community and how it evolves over time endocrine gland – a gland that produces hormones endocrine system – the system in the body that is made up of endocrine glands that produce hormones that are released directly into the blood and transported to target organs around the body endolymph – fluid found in the membranous labyrinth of the ear epidermis – the outer, protective layer of the human skin eustachian tube – a tube from the pharynx to the middle ear that equalises pressure on either side of the ear drum/tympanic membrane evolution – the changes that take place in organisms, often over millions of years but also in recent time, to form new species exponentially – something that is increasing very rapidly in large amounts or numbers fatty liver – a form of liver disease in which the organ is infiltrated with fatty deposits which prevent it from functioning correctly femidom – a barrier method of contraception, a sheath that is inserted into the vagina, which also covers the external genitalia in a woman to prevent sperm from entering the vagina and so the Fallopian tubes fertilisation – process where pollen is transferred from the anther to the stigma of a plant floral whorls – part of the flower that includes the calyx, corolla, androecium and gynaecium (all attached to the receptacle) fossil record – a term used by people who study fossils and evolutionary biology to refer to the total number of fossils that have been discovered as well as the information derived from them gametes – the ova and sperm or sex cells in an organism gene – a sequence of nucleotides that codes for the amino acid sequence of an enzyme or other protein gene pool – the sum total of all the alleles that are found in breeding population of a particular species genetics – the study of how characteristics are transmitted from one generation to another genome – an organism’s entire hereditary information, encoded either in DNA or RNA (in many types of virus) genotype – the alleles that an individual receives at fertilisation geographic barrier – a feature such as a river, a sea or a mountain, which stops species from meeting

Glossary

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