Cambridge International A Level Biology Revision Guide

Cambridge International A Level Biology
6 a Explain the meaning of the term excretion. [3]
b The figure is a photomicrograph of part of the kidney.
A
B
C
Magnification: ×180
D
i Name A, B, C and D. [4]
ii Identify the region of the kidney shown in the figure and give a reason for your identification. [2]
iii Calculate the actual maximum width of the structure labelled A. Show your working. [2]
[Total: 11]
7 The control of the water content of the blood is an example of homeostasis.
a Name the part of the body that monitors the water potential of the blood. [1]
326
In an investigation of the factors that influence urine production, a person drank one litre of water. The
person’s urine was collected at half-hourly intervals for four hours after drinking. The results are shown as
line A on the figure. On the following day, the same person drank one litre of a dilute salt solution and the
urine was collected in the same way (line B). Dilute salt solution has about the same water potential as
blood plasma.
500
Urine output / cm 3 per 30 min
400
300
200
100
A
B
0
0 1 2 3 4 5
Time / h
time of drinking
b Calculate how much urine was produced in the two hours after drinking the litre of water. [1]
c Explain why the person produced so much urine after drinking the litre of water. [4]
d Suggest why the results during the second day were so different from those on the first day. [2]
e Explain why negative feedback, and not positive feedback, is involved in homeostatic mechanisms. [5]
[Total: 13]