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CAIE IGCSE Biology 13 Excretion in Humans

Review the organs and processes that remove metabolic waste, including lung excretion, urine formation and liver production of urea.

Syllabus
2026–2028
Course
Biology 0610

Covered syllabus points

13.1 Excretion in humans

13. Excretion in humans question 1

[Maximum number: 14]

The kidney is an organ in the excretory system.

Question (a)

(a)

Describe what is meant by the term excretion.

[ 2 ]

Question (b)

(b)

State the name of the substance excreted by the lungs.
(c) Fig. 4.1 shows a simplified diagram of a cross-section of a kidney.

Fig. 4.1

Fig. 4.1

[ 1 ]

Question (c)

(c)

State the names of the parts labelled P, Q and R in Fig. 4.1.
P

Q

R
(d) Fig. 4.2 shows the structure of a kidney nephron.

Fig. 4.2

Fig. 4.2

[ 3 ]

Question (d)

(d)

Describe and explain the difference in the composition of the fluids in structures X, Y and Z in Fig. 4.2.

[ 6 ]

Question (e)

(e)

The liver is also involved in excretion.

Describe two ways that amino acids are processed in the liver.
1
2

[ 2 ]

13. Excretion in humans question 2

[Maximum number: 2]

Question (a)

(a)

The carbon dioxide produced during exercise is excreted. Urea is another substance that is excreted.

[ 2 ]

Question (i)

(i)

State the name of the organ that produces urea.

[ 1 ]

Question (ii)

(ii)

State the name of the organ that excretes urea.

[ 1 ]

13. Excretion in humans question 3

[Maximum number: 1]

The diagram shows the human excretory system.
Which labelled structure is the urethra?

Figure for Question 13. Excretion in humans question 3 — CAIE IGCSE Biology

13. Excretion in humans question 4

[Maximum number: 9]

All living organisms excrete waste products.

Question (a)

(a)

Urea is a toxin that is excreted by the kidneys in humans.

Describe how and where in the body urea is formed.

[ 3 ]

Question (b)

(b)

Fig. 3.2 shows part of the human excretory system and associated blood vessels.

The arrows indicate the direction of blood flow.

not to scale

not to scale

[ 1 ]

Question (i)

(i)

Draw a label line and the letter X on Fig. 3.2 to show the location of the cortex in one of the kidneys.

[ 1 ]

Question (c)

(c)

Doctors wanted to investigate the effect of exercise on the excretion of salts.

They collected urine from people before and after running a long distance on a hot day.
The results of their investigation are shown in Table 3.2.

Table 3.2

Table 3.2

[ 5 ]

Question (i)

(i)

Suggest why there is a difference in the volume of urine produced before running compared with after running.

Use the information in Table 3.2 in your answer.

[ 2 ]

Question (ii)

(ii)

Describe how the kidney tubules enable the excretion of salts.

[ 3 ]
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