AQA GCSE Biology Paper 2 Higher November 2021 question paper 8461/2H

The nucleus of a cell contains DNA.

Name the structures inside the cell nucleus that contain DNA.

Figure 1 shows part of a DNA molecule.

Name the part of the DNA molecule labelled X.

What type of substances are labelled A, C, G and T in Figure 1 ?

Figure 2 shows another section of a DNA molecule.

Four of the substances you named in Question 01.3 are not labelled in part Y of Figure 2. Label each of these substances with the correct letter, A, C, G or T. Use information from other parts of Figure 2 to help you.

What is happening to the DNA in part Z of Figure 2 ? Tick (✓) one box.

A gene is a length of DNA. What type of substance does a gene code for?

Most human body cells contain 6 10^–12 grams of DNA. What mass of DNA will a human sperm cell contain? Tick (✓) one box.

What is the name of the type of cell division that produces sperm cells? Tick (✓) one box.

A student investigated the effect of temperature on the decay of milk. Figure 3 shows the apparatus the student used.

This is the method used.

1. Set up the apparatus as shown in Figure 3 with the milk at 20 C.

2. Record the pH over 5 days using the computer.

3. Repeat with another batch of fresh milk at 25 C.

How could the student keep the milk at a constant temperature for 5 days?

Give one variable the student should keep constant. Do not refer to temperature in your answer.

Table 1 shows the student’s results for the milk at 20 C.

Complete Figure 4. You should:

• label the x-axis

• use a suitable scale for the x-axis

• plot the data from Table 1

• draw a line of best fit.

The data you plotted in Question 02.3 were obtained at 20 C. Sketch a line on Figure 4 to show the results you would expect at 25 C.

Human body temperature is controlled within very narrow limits. Scientists investigated the effect of drinking ice-cold water on:

• internal body temperature

• the rate of sweating.

This is the method used.

1. Sit a person inside a room kept at a constant temperature of 25 C.

2. Measure the person’s internal body temperature near the brain.

3. Measure the person’s rate of sweating.

4. After 20 minutes, give the person 500 cm³ of ice-cold water to drink.

5. Continue to measure the person’s internal body temperature and sweating rate for a further 50 minutes.

Give the reason why the person should not move during the investigation.

Figure 5 and Figure 6 show the scientists’ results.

What is this person’s normal internal body temperature? Tick (✓) one box.

The results show that when the ice-cold water was drunk, the temperature near the brain decreased.

Explain why the temperature near the brain decreased.

The thermoregulatory centre in the brain responds to the decrease in temperature. How does the thermoregulatory centre send information to sweat glands in the skin?

The rate of sweating changes between 24 minutes and 36 minutes. Explain how this change helps to maintain the person’s normal body temperature.

During exercise, the skin appears red. What causes the skin to appear red? Tick (✓) one box.

Decay occurs in a compost heap. Figure 7 shows a compost heap.

Describe:

• how microorganisms in the layers of soil help to recycle chemicals in the dead plants

• how the chemicals are used again by living plants.

The growth of daisy plants on a lawn is affected by biotic factors and by abiotic factors.

Table 2 shows six factors. Tick () one box in each row to show whether the factor is biotic or abiotic.

Figure 8 shows a plan of a garden.

A student estimates the number of daisy plants growing on the lawn. The student places a quadrat at 10 different positions on the lawn. The quadrat measures 50 cm 50 cm. The student counts the number of daisy plants in each quadrat.

How should the student decide where to place the quadrat? Give the reason for your answer.

The mean number of daisy plants in each quadrat is 6. Calculate the number of daisy plants on the lawn. Give your answer to 3 significant figures.

Number of daisy plants on the lawn =

Using the mean from this investigation to calculate the number of daisy plants on the lawn may not be accurate. Give two reasons why.

Reflex actions are coordinated by the nervous system.

What is meant by the term ‘reflex action’?

A woman’s hand accidentally touches a hot object. The woman moves her hand away rapidly. Describe how the woman’s nervous system coordinates the reflex action.

The endocrine system coordinates many internal functions of the body. Give three ways coordination by the endocrine system is different from coordination by the nervous system.

Describe how hormones control the menstrual cycle.

A food web contains several food chains. Figure 9 shows a food web.

The animals in Figure 9 get their energy by eating other organisms. Describe how the algae get energy.

Name one primary consumer in Figure 9.

Name one producer in Figure 9.

The different food chains in Figure 9 have different numbers of organisms. Complete Figure 10 to show a food chain in Figure 9 with five organisms, including the human.

Figure 9 shows that mackerel eat krill and squid. The biomass of mackerel is much less than the combined biomass of krill and squid. One reason for this is that the mackerel cannot digest all parts of the krill and squid. Give two other reasons.

Figure 11 shows how the biomass of adult herring in the North Sea has changed

between 1950 and 2010.

Calculate the percentage decrease in the biomass of herring between 1960 and 1977. Give your answer to the nearest whole number.

Too many herring were caught by fishermen between 1960 and 1977. Herring can live for up to 12 years and begin to reproduce when 3 to 4 years old. Laws have been introduced to help conserve herring:

• 1977 to 1981 – herring fishing was banned in the North Sea

• 1984 to present day – control of mesh size of fishing nets

• 1997 to present day – fishing quotas were introduced

• 1998 to present day – herring fishing was banned in breeding grounds during the breeding season.

Figure 12 shows how a minimum mesh size helps to conserve herring.

Figure 11 is repeated below.

Evaluate the effect of these laws on the conservation of herring stocks.

Use data from Figure 11 and information from Figure 12 in your answer.

Sickle cell anaemia is an inherited condition that affects red blood cells. Sickle cell anaemia is caused by a mutation in the gene for haemoglobin. Haemoglobin is the red pigment found in red blood cells. A person who is homozygous for the normal haemoglobin allele (H^A) produces normal red blood cells. A person who is homozygous for the mutated allele (H^S):

• produces red blood cells with abnormal haemoglobin

• has red blood cells that can form an altered shape

• has sickle cell anaemia and becomes ill.

A person who is heterozygous:

• has both normal and abnormal haemoglobin in the red blood cells

• has sickle cell trait

• is generally healthy but can become ill in certain circumstances.

Give the reason why a mutation in the gene coding for haemoglobin could be harmful.

Figure 13 shows some red blood cells from the blood of a person with sickle cell trait.

Calculate the proportion of cells in Figure 13 that have an altered shape.

Figure 14 shows the inheritance of sickle cell anaemia in one family.

Persons 8 and 9 in Figure 14 are expecting a second child. Determine the probability that the child will be a girl with sickle cell trait. You should:

• draw a Punnett square diagram

• identify the phenotype of each offspring genotype

• use the symbols: H^A = normal haemoglobin allele H^S = mutated haemoglobin allele.

Without medical treatment, people with sickle cell anaemia are frequently ill and have a reduced life expectancy. The malarial parasite cannot live in the red blood cells of a person who has

A scientist stated: ‘It is an advantage for people to have the H^S allele in countries where malaria occurs.’ Evaluate the scientist’s statement.

The Galapagos Islands are located in the Pacific Ocean. Several species of birds called finches live on the Galapagos Islands. These finches are very similar to each other. Figure 15 shows two modern species of Galapagos finch and their classification.

Figure 15

Medium ground finch Small ground finch

Complete Figure 15 to give the names of the missing classification groups.

Give the binomial name of the medium ground finch. Use information from Figure 15.

In each species of finch, there is a variation in beak depth.

Figure 16 shows how beak depth is measured.

Figure 17 shows the relationship between the beak depth of parent birds and the beak depth of their offspring.

Give evidence from Figure 17 that beak depth is an inherited characteristic.

Scientists suggested that more than one gene controls beak depth. Give evidence from Figure 17 to support the scientists’ suggestion.

Figure 18 is a map of the Galapagos Islands.

On Isabela Island, the medium ground finch and the small ground finch are found. On Daphne Island, only the medium ground finch is found. On Crossman Island, only the small ground finch is found. Figure 19 shows how the beak depth of each species varies on each island.

The medium ground finch and the small ground finch both feed on seeds.

The size of seeds eaten by each bird depends on the depth of the bird’s beak.

The range of beak depth of medium ground finches on Isabela Island is different from the range on Daphne Island. Explain what might have caused this difference.

Figure 19 shows:

• the two species of finch live on Isabela Island

• only one of the species lives on Daphne Island

• only one of the species lives on Crossman Island.

Suggest why both species of finch are able to live on Isabela Island.