Cambridge Secondary (7-9). Stage 9. MCE Science. Student Book - Unit 2: Excretion

How much water do you drink in a day?

If our bodies already contain so much water, why do we still have to drink water every day? Think about what happens when you exercise or when it is a very hot day: you perspire. Every time you use the toilet, you are losing water.

What organs are responsible for maintaining the correct amount of water in our bodies?

How does human waste affect the environment?

What happens on a day when you drink a lot of water? What do you notice about the amount and colour of your urine? What about on a day when you drink less water?

The mineral salts found in commercial fertilisers include nitrates. Nitrates are also found in urine. Think back to the question at the start of the chapter. How does human waste affect the environment?

How can infrastructure be developed to change the way human urine is discarded so that it helps rather than harms the environment?

Work in groups. Do some research using the Internet or other sources. Are there any benefits of having two kidneys?

Work in groups. Do some research using the Internet or other sources. Find out about the ethics of donating kidneys while alive, including risks.

Work in groups. Do some research using the Internet or other sources. Do the ethical considerations change when a donor is no longer alive?

Share your findings with the class. Discuss the pros and cons of kidney donation.

Name the components of urine.

How does the excretory system work to keep the body healthy?

What will happen to the body if the kidneys stop functioning?

The diagram below shows the human excretory system.



Write the names of the parts labelled A to D.

The diagram below shows the human excretory system.



Which part, A, B, C or D, of the excretory system filters the blood?

The kidneys are important organs in our body. Tick (✓) the box next to each statement that is true.

The kidneys are important organs in our body. The statements in part a are:
- A. Urine leaves the body through the ureters.
- B. The kidneys digest food.
- C. Structures in the kidney filter the blood and then return nutrient-rich blood back into the body.
- D. Urine is made up of mostly water.

Rewrite each false statement in a so that it is true.

The pie chart shows the composition of urine. Label the pie chart showing the components of urine. Use words from the list below.

urea · water · salts and uric acid

The kidneys are part of the human excretory system. Complete these sentences about how a kidney works. Use words from the list below.

vein · urethra · ureters · artery · filters · urine

Unfiltered blood enters the kidney through the renal __________.
The kidney __________ the blood.
Filtered blood re-enters the bloodstream through the renal __________.
The __________ formed enters the bladder through the __________ and is excreted through the __________.