AQA GCSE Biology Paper 2 Higher June 2019 question paper 8461/2H

Figure 1 shows a food chain in a pond.

Which term describes the Daphnia in this food chain?

Tick (✓) one box.

Draw a pyramid of biomass for the food chain.

Label each trophic level.

Give one reason why the total biomass of the Daphnia in the pond is different from the total biomass of the algae.

Students investigated the size of the population of Daphnia in the pond.

This is the method used.

1. Collect 1 dm³ of pond water from near the edge of the pond.

2. Pour the water through a fine net.

3. Count the number of Daphnia caught in the net.

4. Repeat steps 1–3 four more times.

Table 1 shows the results.

Calculate the mean number of Daphnia in 1 m³ of pond water.

The pond was a rectangular shape, measuring:

• length = 2.5 metres

• width = 1.5 metres

• depth = 0.5 metres.

Calculate the estimated number of Daphnia in the pond.

Use your answer from Question 01.4.

Give your answer in standard form.

Rainfall can cause fertiliser to be washed from farmland into a pond.

The students investigated the effect of fertiliser on the population of Daphnia in water from the pond.

• The students put 20 Daphnia in each of five different concentrations of fertiliser.

• The students counted the total number of Daphnia in each concentration of fertiliser after 2 weeks.

Figure 2 shows the results.

A concentration of 5.0 mg/dm³ of fertiliser caused a large increase in the population of Daphnia.

Explain why.

Figure 1 is repeated below.

The population of Hydra will decrease when 20 mg/dm³ of fertiliser is added to the pond.

Explain why.

Genetic material is made of DNA.

Which structures in the nucleus of a human cell contain DNA?

Figure 3 shows part of one strand of a DNA molecule.

Label parts X, Y and Z on Figure 3.

Choose answers from the box.

A complete DNA molecule is made of two strands twisted around each other.

What scientific term describes this structure?

DNA codes for the production of proteins.

A protein molecule is a long chain of amino acids.

How many amino acids could be coded for by the piece of DNA shown in Figure 3 ?

Tick (✓) one box.

Scientists have now studied the whole human genome.

Give two benefits of understanding the human genome.

Phototropism is a growth response by part of a plant to light.

Name one other tropism.

Give the stimulus the plant responds to in the tropism you have named.

Plan an investigation to show the effect of light from one direction on the growth of plant seedlings.

Include details of any controls needed.

You may use some of the equipment shown in Figure 4 and any other laboratory apparatus.

Explain how phototropism in a plant shoot helps the plant to survive.

The human eye can focus on objects at different distances.

Figure 5 shows how a clear image of a distant object is formed in a person’s eye.

Explain how the person’s eye could adjust to form a clear image of a nearer object.

Explain why a long-sighted person has difficulty seeing near objects clearly.

Long-sightedness can be corrected by wearing spectacles.

Describe how spectacle lenses can correct long-sightedness.

Table 2 gives the classification of four plant species.

Species 1 and 3 are the most closely related.

What information in Table 2 gives evidence for this?

Figure 6 shows the inheritance of flower colour in two species of plant.

• In pea plants and in snapdragon plants, flower colour is controlled by one pair of alleles.

• In Figure 6 the parental generation plants are homozygous for flower colour.

• In heterozygous pea plants, the allele for red flower colour is dominant.

• In heterozygous snapdragon plants, the alleles for flower colour are both expressed.

Use the following symbols for alleles in your answers to Questions 05.2 to 05.4:

Pea plants
Snapdragon plants

R = allele for red flowers C^R = allele for red flowers r = allele for white flowers
C^W = allele for white flowers

What is the genotype of the red-flowered pea plants in the F₁ generation?

What is the genotype of a white-flowered snapdragon plant?

A gardener crossed two pink-flowered snapdragon plants.

Draw a Punnett square diagram to show why only some of the next generation plants had pink flowers.

Identify the phenotypes of all the offspring plants.

What percentage of the offspring would you expect to have pink flowers?

Commercially, hundreds of pink-flowered snapdragon plants can be produced from one pink-flowered plant.

Figure 7 shows a tissue culture technique used for producing many plants from one plant.

Give a reason for each of the following steps shown in Figure 7.

Several groups of cells are scraped off the leaf:

Nutrients are added to the agar jelly:

Hormones are added to the agar jelly:

The plant cells are kept in sterile conditions:

The plant cells are kept at 20^oC:

Explain why the method shown in Figure 7 produces only pink-flowered plants.

Water conservation is important to the human body.

Which gland releases the hormone that controls water loss from the body?

Tick (✓) one box.

Which hormone helps the kidneys to control water loss from the body?

Tick (✓) one box.

A man is walking across a desert.

The man has used up his supply of drinking water.

Explain how the gland you named in Question 06.1 and the kidneys reduce water loss.

Some people have kidney failure.

Doctors may treat patients with kidney failure by either:

• dialysis

• a kidney transplant.

Explain two biological reasons why most doctors think that a kidney transplant is a better method of treatment than dialysis.

Do not refer to cost or convenience.

Ragwort is a weed that grows on farmland.

Ragwort is poisonous to horses.

Plan an investigation to estimate the size of a population of ragwort growing in a rectangular field on a farm.

The herbicide glyphosate will kill ragwort and other weeds.

Scientists use bacteria for the genetic engineering of crop plants to make the crops resistant to glyphosate.

Figure 8 shows the growth of a culture of the bacteria in a solution of nutrients at 25 C

Why did the rate of reproduction increase between 2 hours and 7 hours?

After 12 hours, the rate of reproduction decreased.

Suggest three ways the scientists could maintain a high rate of reproduction in the bacterial culture.

The rate of reproduction of the bacteria is fastest at 7 hours.

How many times faster is the rate of reproduction at 7 hours than the rate at 12 hours?

Scientists transferred a gene for resistance to the herbicide glyphosate into the bacteria.

The genetically-modified (GM) bacteria can then transfer the glyphosate-resistance gene to a crop plant.

Explain the advantage of making crop plants resistant to glyphosate.

It is important to keep the blood glucose concentration within narrow limits.

A person eats a meal containing a lot of carbohydrate. This causes an increase in the person’s blood glucose concentration.

Explain how the hormones insulin and glucagon control the person’s blood glucose concentration after the meal.

The body cells of a person with Type 2 diabetes do not respond to insulin.

A person with Type 2 diabetes often has a higher blood insulin concentration than a non-diabetic person.

Explain why.

Metformin is a drug used for treating people who have Type 2 diabetes.

Scientists investigated the effects of metformin and two other drugs, A and B.

The scientists wanted to see how the drugs affected the blood glucose concentrations of 220 people with Type 2 diabetes.

This is the method used.

1. Put the 220 people into five groups.

2. Treat each group with a different drug or combination of drugs for several weeks.

3. Give each person a meal high in carbohydrate.

4. Measure the blood glucose concentration of each person 30 minutes after the meal and again 3 hours after the meal.

Suggest three variables that the scientists should have controlled in the investigation.

The scientists recorded their results as a mean value for each group.

The scientists calculated the ‘standard deviation’ for each group’s result.

Standard deviation is a measure of the spread of the individual results above or below (±) the mean value.

The scientists gave each group’s result as:

mean ± standard deviation

The larger the standard deviation, the greater is the spread of results around the mean.

Which of the results is the most precise?

Tick (✓) one box.

Table 3 and Figure 9 show the scientists’ results.

In Table 3 and Figure 9 some standard deviations of results overlap.

• An overlap of standard deviations shows the difference between the means is not significant.

• No overlap of standard deviations shows a significant difference between the means.

A student looked at the scientists’ method and the results in Table 3 and Figure 9.

The student stated:

‘Metformin works better when used with other drugs.’

Evaluate the student’s statement.