AQA GCSE Trilogy Biology Paper 2 Higher June 2023 question paper 8464/B/2H

Sexual reproduction in humans involves the production of egg cells and sperm cells.

Name the type of cell division that produces egg cells and sperm cells.

Sexual reproduction produces offspring that are genetically different from each other. Give two reasons why sexual reproduction causes variation in the offspring.

Polydactyly is an inherited disorder.

The allele for polydactyly is dominant, D. A person with two copies of the allele d will not have polydactyly.

A person with the genotype DD is homozygous. What word describes the genotype Dd ?

A person with the genotype Dd and a person with the genotype dd plan to have a child. Determine the probability that the child will have polydactyly. You should:

• complete the Punnett square diagram

• identify any offspring genotype that would have polydactyly.

Embryos can be screened for the alleles that cause inherited disorders. Give two advantages of embryo screening.

It is estimated that 99.9% of all species that have ever existed are now extinct.

Why is the percentage of species that are extinct only an estimate? Tick (✓) one box.

What evidence is used to study species that have become extinct?

A bacterium called Clostridioides difficile (C. difficile) can infect the human digestive system. C. difficile can multiply and produce toxins. The toxins cause diarrhoea. Doctors are concerned that new strains of C. difficile may evolve. Antibiotics may not be able to kill these new strains. Explain how the evolution of antibiotic resistant C. difficile can be slowed down.

Figure 1 shows a river next to a field.

Describe a method to investigate how the distance from the river affects the number of different plant species in the field. You should explain how to use a transect in your method.

Students used a valid method to investigate how the distance from the river affects the number of different plant species in the field. Figure 2 shows the results.

What is shown by the data in Figure 2 ? Tick (✓) one box.

Cows walk on the ground near the river more than they walk on the ground further

from the river.

Which is an abiotic factor that could affect the number of different plant species found near the river? Tick (✓) one box.

Increasing numbers of cows are being farmed across the world. Explain the environmental implications of increasing numbers of cows being farmed.

Sea lice are small animals that feed on the skin and blood of salmon fish. Figure 3 shows sea lice attached to the skin of a salmon, Oncorhynchus keta.

What is the genus name of salmon?

Which domain are sea lice classified in?

Some salmon have genes that result in fewer sea lice attaching to the skin. Describe how fish farmers can selectively breed salmon that sea lice cannot attach to.

Explain the advantages to salmon farmers of producing salmon that do not have sea lice attached to their skin.

Explain the disadvantage of selectively breeding salmon. Do not refer to cost or to time in your answer.

In Vitro Fertilisation (IVF) can be used to treat infertility.

Which hormones are given to women having IVF treatment? Tick (✓) one box.

Name the target organ of the hormones used for IVF.

Describe why microscopes are needed in the process of IVF.

Describe how the hormones given to women during IVF treatment interact with other hormones to prepare the body for pregnancy.

Scientists studied women who had IVF treatment. Table 1 shows the results.

Calculate the simplest ratio of the number of women who had successful IVF to the number of women who had unsuccessful IVF. Give the ratio in whole numbers.

Suggest one factor that can affect the probability of a woman having a child as a result of IVF treatment.

Give two arguments against the use of IVF treatment. Do not refer to cost or to religion in your answer.

The control of body temperature is an example of homeostasis.

Give one other internal condition controlled by homeostasis. Do not refer to temperature in your answer.

Explain why the control of body temperature is important.

The body temperature of long-distance swimmers can change as the

length of time swimming in cold water increases. Figure 4 shows how the body temperature of one swimmer changed in the first 4 hours of a long-distance swim.

Calculate the mean rate of body temperature decrease per hour in the first 4 hours of the swim.

Hypothermia is a dangerously low body temperature. For this swimmer, a 5.5% decrease in body temperature from the start of the swim will cause hypothermia. Determine the body temperature at which this swimmer will start to have hypothermia. Give your answer to 2 significant figures.

A decrease in body temperature causes the adrenal glands and the thyroid gland to

be stimulated.

Which gland secretes hormones to stimulate the adrenal glands?

Explain the role of the adrenal glands in responding to a decrease in body temperature.

Explain how the thyroid gland controls the response to a decrease in body temperature by negative feedback.