Variation

Genes control natural hair colour in humans.

Which term describes the differences in hair colour?

Genes are found on chromosomes.

Name the part of the human cell where chromosomes are found.

The hair colour of 24 students was recorded.

Figure 1 shows the results.

Complete Figure 2 to show the tally and the total for brown hair.

Complete the bar chart to show the totals in Figure 2 and label the x ‑axis.

Apple trees show genetic variation.

State one possible cause of genetic variation in apple trees.

The colour of an apple is an observable characteristic.

Which is the term for an observable characteristic?

Name the type of reproduction that produces genetically identical organisms.

Grafting is a technique used to grow some varieties of apple tree.

Figure 9 shows apple tree shoots grafted on to a rootstock.

Grafting can be used to produce apple trees that are genetically identical.

Give one advantage and one disadvantage of growing genetically identical apple trees.

advantage

disadvantage

As apples ripen, enzymes convert starch into sugars.

Devise a method to find the optimum pH of an enzyme that breaks down starch.

You may use standard laboratory equipment and the solutions listed in the box.

The optimum pH of an enzyme is pH 6.

Explain why this enzyme would not work at pH 10.

In the 19th century the destruction of wetland habitats caused the extinction of the bittern in the UK.

Figure 5 shows a bittern.

Restoration of the habitats has led to the birds returning to the UK.

Male bitterns make a loud booming sound.

This allows the numbers of male bitterns to be counted.

In 1997, 11 males were counted and this increased to 221 males in 2021.

Calculate the percentage increase in the number of males from 1997 to 2021.

The bitterns are difficult to see in the reeds of the wetland habitat.

Give one benefit of this to the bittern.

There is some concern that the bitterns in the UK are all closely related. This could make them susceptible to extinction.

Explain, using your knowledge of natural selection, why being closely related could make the bitterns susceptible to extinction.

Describe how selective breeding can be used to produce a large population of animals that are not closely related.

Sex determination in birds is different from humans.

Males are homozygous Z and females are heterozygous ZW.

Complete the Punnett square to show how sex is determined in birds.

A person’s mass is partially influenced by the alleles they inherit from their parents.

Give two other factors that can influence a person’s mass.

Figure 8 shows the data obtained from a patient by a doctor doing a health check.

The guidance used by the doctor is also listed in Figure 8.

Comment on the data and the health risks to this patient.

* (c) The doctor also tested the reaction time of the patient.

Describe the structure and function of a reflex arc.

Stone tools can be found at sites used by our human ancestors.

Describe how tool P was made.

Figure 4 shows tool Q which was found at the same site as tool P.

A scientist stated that tool Q was made by a more evolved human ancestor than tool P.

Which observation supports this statement?

Tools provide evidence for human evolution.

Use words from the box to complete the sentences.

Evolution is the change of inherited characteristics through

These changes occur because genes_........ .

Fossils were also found in the soil around tool Q.

Describe two ways that stone tools and fossils can be dated to find out how old they are.