The body cells of a species of fish contain 30 chromosomes, in 15 pairs.
.1
Give the number of chromosomes in one of this fish's gametes.
[1 mark]
.2
Give the number of chromosomes in a fertilised egg cell of this fish.
[1 mark]
.3
Describe what happens to the chromosomes when a cell divides by meiosis to form gametes.
[3 marks]
6 marksFoundation and Higher
Spec and skills
Original practice question
Answer and supported method checks
Tobacco mosaic virus (TMV) infects tomato and tobacco plants. HIV infects humans.
.1
TMV causes a mosaic pattern of discoloured patches on the leaves.
Explain why an infected plant grows more slowly.
[3 marks]
.2
Explain how viruses make people ill.
[2 marks]
.3
How is HIV controlled in a person who is infected?
[1 mark]
8 marksFoundation and Higher
Spec and skills
Original practice question
Answer and supported method checks
A student models a small organism as a cube with sides 3 cm long.
.1
Calculate the total surface area of the cube.
[2 marks]
.2
Calculate the volume of the cube.
[1 mark]
.3
Calculate the surface area to volume ratio of the cube.
[1 mark]
.4
A larger organism has a smaller surface area to volume ratio.
Explain why a large multicellular organism needs exchange surfaces and a transport system.
[2 marks]
.5
Explain why root hair cells need energy to take in mineral ions from the soil.
[2 marks]
5 marksFoundation and Higher
Spec and skills
Original practice question
Answer and supported method checks
A student investigated the effect of pH on the time taken for amylase to break down starch.
She mixed amylase, starch and a buffer solution in a water bath at 35 °C. Every 30 seconds she put a drop of the mixture onto iodine solution on a spotting tile. She recorded the time when the iodine no longer turned blue-black.
Time for starch to be broken down: pH 5, 150 s; pH 6, 90 s; pH 7, 60 s; pH 8, 120 s; pH 9, 240 s.
pH
Time for starch to be broken down (s)
5
150
6
90
7
60
8
120
9
240
.1
The rate of reaction can be found with:
rate =time1000
Calculate the rate of reaction at pH 7.
[1 mark]
.2
Explain why the starch took much longer to break down at pH 9.
[2 marks]
.3
Suggest how the student could find the optimum pH of amylase more precisely.
[1 mark]
.4
Sampling every 30 seconds limits the accuracy of the times.
Explain why.
[1 mark]
3 marksFoundation and Higher
Spec and skills
Original practice question
Answer and supported method checks
Evolution is a change in the inherited characteristics of a population over time through natural selection.
.1
Put the stages of natural selection in order, starting with the first.
