3.1) Copy and complete these sentences using words from the list. You may use cach word once, more than once or not at all.

blood                   contracts                   muscle                   stretches                   tubes                   valves
The heart is made of ................... This muscle ................... and relaxes rhythmically, pumping blood around the body. There are ................... inside the heart that make sure the blood keeps flowing in the correct direction.

3.2) The diagram represents the circulatory system.

a: Write down three letters that show arteries.
b: Write down one letter that shows capillaries.
c: Write down two letters that show veins.
d: Write down three letters that show vessels containing deoxygenated blood.

3.3) Krystyna investigated how a person's pulse rate changes when they exercise. She tested four of her friends. Belinda and Jasmina do a lot of sport. Jade and Mara prefer to read books and play computer games.
Krystyna measured the four girls' pulse rates, in beats per minute, when they were relaxing Then she asked them to run up two flights of stairs, and measured their pulse rates again. These are her results.
Belinda 65/102
Jasmina 72/105
Jade 70/110
Mara 74/120
a: Draw a results table, and fill in Krystyna's results. Remember to label the rows and columns of your results table fully:
b: Display Krystyna's results in the way you think is best.
c: Write down one conclusion that Krystyna can make from her results.
d: Krystyna decided that she did not have enough evidence to decide whether being fit affects a person's pulse rate. Was she right? Explain your answer

3.4) The diagrams show two blood cells.

a: Make a copy of the drawing of the red blood cell. Label the cell membrane and the cytoplasm.
b: Name one structure that most cells have, but that red blood cells do not have.
c: Describe one other way in which red blood cells differ from most other cells in the human body.
d: Explain how red blood cells are adapted to carry out their function.
e: Describe the function of white blood cells.