Student’s Book 6
1 What are the main parts of the circulatory system?
2 Look at the blood vessels on the diagram on page 6. Which are veins and which are arteries? How do you know?
3 What are you actually feeling when you take your pulse?
4 What makes your blood flow and move around your body? Why is this important?
Before you do activity 1 below, remind yourself of the three types of variables involved in a fair test investigation. The dependent variable is the variable that is being investigated. The independent variable is the variable that is changed during the investigation. The control variable is the variable that is kept the same throughout the investigation. g
Activities
You can feel your heartbeat or pulse where blood vessels are close to the skin. The inside of your wrist and the side of your throat are good places for doing this.
1
Plan a fair test investigation, identifying the independent, dependent and control variables. to find out what happens to your pulse rate after three different types of exercise. Use Workbook pages 4–6 to record your investigation.
2
I have learned I
Find out how each of these affects your heart: fat, exercise, salt, smoking, and caffeine in coffee or fizzy drinks.
3
Design an information leaflet to tell adults what they can do to keep their heart healthy.
● The circulatory system is the body’s transport system. Nutrients from food, oxygen and waste are transported round the body in the blood.
● The heart pumps blood around the body in the circulatory system.
1.8 History of science: Human anatomy
The study of the human body is called anatomy. Anatomical paintings at least 25,000 years old have been found in caves in Western Europe, Africa, Asia and Australia.
The first scientific advances in anatomy took place in Ancient Greece between 500 and 300 BCE. Hippocrates and Aristotle learned about anatomy by dissecting animal bodies. Herophilus was a Greek doctor who dissected human bodies. He argued that the brain was the centre of the body, not the heart as Aristotle believed.
Arab doctors continued to study and learn about anatomy. Between 950 and 1300 CE they made many discoveries: Ibn Al-Haytham wrote about how the eyes work, Abu Ibn Sina (Avicenna) wrote a famous book called the Canon of Medicine, and Ibn Al-Nafis explained how the circulatory system works.
From the year 1000 onwards, Italian medical schools used translations of Arabic works and the first manual of human dissection was developed.
In the 1500s, a Belgian student called Vesalius decided to check and correct Galen’s work. He wrote seven books based on detailed dissection work he did at Padua University, which was also home to the first anatomy theatre. This was a room where people could come to watch human dissections.
Key words
• anatomy
• dissect
Ancient Roman doctors learned about anatomy from treating wounded soldiers. It was against the law to dissect human bodies, so they used animals to develop theories. Galen (129 c.210 CE) developed theories based on animal bodies. Some of his theories were wrong, but they remained unchallenged for hundreds of years.
In 15th-century Europe, artists like Leonardo Da Vinci made anatomical sketches of the human body, often using dissections to do this.
3.7 Temperature and dissolving
solute
solution
Do you remember the science words used to talk about dissolving? that
Water is the solvent. Sugar is the solute. The solute dissolves in the solvent.
You already know that some solids can dissolve in liquid and that dissolving is a physical change which can be reversed. Substances that dissolve in water are said to be soluble. Those that do not dissolve are said to be insoluble.
The end result is a sugar solution.
A class decided to investigate if the temperature of water affects how long it takes for a sugar cube to dissolve.
1 What do you think the students should do to find out how the temperature of water affects the rate of dissolving? Why?
When you measure the time it takes for something to happen, you should repeat your measurements to make sure your results are reliable. Repeated measurements also allow you to work out the mean (average) time that something takes.
These students are carrying out the investigation.
2 What is each student doing? Why is each task necessary?
3 Identify the independent, dependent and control variables.
The students repeat their experiment three times. The table and dot plot show the results that one group of students got.
4.2 Weight, mass and gravity
In the previous unit you learned that objects have weight because gravity pulls them towards the Earth. You also saw that the weight of an object can be measured in newtons using a newton meter.
The stronger the pull of gravity on an object, the more it weighs. Similarly, if the force of gravity is weak then the object will weigh less. Objects weigh more on Earth than they do on the Moon, because gravity on Earth is about six times stronger than gravity on the Moon.
All objects are made of matter. The mass of an object tells you how much matter is in the object. Mass is measured in kilograms and grams
In science, mass is measured using a beam balance. To find the mass of an object, you place it on one end and standard mass pieces are moved along the scale until it balances. The mass is then read off the scale.
An apple has a mass of about 100 g. This is about the same as a weight of 1 N when it is measured on Earth.
Mass is not a force. The mass of an object will stay the same (as long as the object doesn’t change) wherever you measure it.