AQA GCSE Trilogy Biology Paper 2 Higher June 2018 question paper 8464/B/2H

Many biotic and abiotic factors can affect the growth of plants.

Are the factors in Table 1 biotic or abiotic? Tick one box for each factor.

Two students investigated the effect of light intensity on the distribution of small plants. The plants are growing under a tree in a park. The students made the following hypothesis: ‘As you move outwards from a tree there will be more plant growth.’

Explain why the students thought their hypothesis would be correct.

The students used two pieces of equipment. Give the scientific name of each piece of equipment.

A square frame measuring 0.5 m × 0.5 m An electronic device to measure light intensity

This is the method used.

1. Fix one end of a tape measure at the base of the tree.

2. Fix the other end of the tape measure 11 metres from the tree.

3. At 0 metres put the square frame on the ground.

4. Identify all the plant species growing inside the frame.

5. Estimate and record the percentage cover of each plant species.

6. Measure the light intensity inside the frame.

7. Put the square frame on the ground every 2 metres along the tape to 10 metres.

8. Repeat steps 4 – 6 in every frame.

Figure 1 shows the equipment in this investigation.

Calculate the total area sampled.

The whole investigation was done as quickly as possible on the same day. Suggest one reason why.

Give one way the investigation could be improved.

Table 2 shows the results.

Which plant species in Table 2 will only grow at high light intensity?

What conclusion can be made about the relationship between light intensity and the total percentage cover of plants? Use data from Table 2 in your answer.

Light intensity might not be the cause of this pattern of plant distribution. Suggest one different factor that may cause these results. Give one reason for your answer.

Reason

Pseudomonas bacteria cause infections in hospital patients. A new strain of Pseudomonas bacteria has evolved. This new strain can only be killed by one antibiotic called fluroquinolone. Scientists want to prevent the new strain of Pseudomonas from spreading in the human population. Explain the advice doctors should be given to prevent the spread of the new strain.

Scientists have removed microorganisms from inside rocks in caves in Mexico. The microorganisms have been trapped there for between 10 000 and 50 000 years. The caves are dark, very hot, humid and acidic.

Why are these microorganisms called extremophiles? Tick two boxes.

The microorganisms have been inactive for thousands of years but the scientists have reactivated them. Figure 2 shows the results of enzyme analysis on four enzymes, A, B, C and D. Three of the enzymes were from microorganisms found in the soil near the caves. One of the enzymes was from a reactivated microorganism from the caves.

Which enzyme comes from the microorganism from the caves? Tick one box.

Give the reasons for your answer to question 03.2

Carl Woese developed the ‘three-domain system’ of classification. Describe the ‘three-domain system’ of classification.

Most of the microorganisms from the caves were classified as belonging to the Archaea domain of the ‘three-domain system’. Suggest why.

This question is about the nervous system. Figure 3 shows a reflex arc.

Name parts P and Q shown on Figure 3

Compare how information is transferred along a neurone with how information is transferred across gap P.

Why does a conscious action take longer than a reflex action?

Information travels at 120 metres per second in neurones. Calculate the time it would take for the information to travel 1.6 m along a neurone. Give your answer in milliseconds.

Doctors tested people of different ages to time how long it took between touching a sharp pin and the arm muscle contracting. Table 3 shows the results.

Describe the relationship between age in years and time for the muscle to contract.

Read the following.

The IR8 variety of rice was produced by selective breeding. Describe the steps the scientists would have taken to produce IR8

The IRRI has now developed several new varieties of genetically modified (GM) rice plants. Some people in India agree and some people disagree with GM varieties of rice being grown. Explain why.

Figure 4 shows how hormone concentrations vary during a normal human menstrual cycle if a woman does not become pregnant.

Calculate the rate of increase in LH concentration between day 9 and day 12 Give your answer in arbitrary units per hour. Give your answer to 2 significant figures.

Describe the sequence of hormone interactions in the menstrual cycle. Name where each hormone is produced.

Progesterone is used in some contraceptives. Suggest one advantage of using a progesterone patch rather than a progesterone oral contraceptive.

Many people eat shellfish called oysters. An oyster has 20 chromosomes in each body cell.

Which arrangement of chromosomes will a male oyster have in each body cell? Tick one box.

Oyster gametes only contain half the amount of DNA compared to a normal oyster body cell. Describe the type of cell division that produces gametes.

Biologists have discovered a way to produce oysters that have three sets of chromosomes (triploid) instead of the usual two sets (diploid). The triploid oysters cannot reproduce and so they grow more quickly. Diploid oysters do not taste good in the reproductive season. Triploid oysters taste good all year. Figure 5 shows the chromosomes in a diploid cell and in a triploid cell. Only two sets of chromosomes are shown.

Suggest why the triploid oysters are not able to reproduce.

Explain why the triploid oysters grow more quickly than the diploid oysters.

The population of diploid oysters growing in the wild has reduced by over 80% in the last 20 years. Suggest two environmental factors which may be causing this reduction. Give a reason why each factor may be causing the reduction in the population.

Oyster farmers grow the triploid oysters from young seed oysters. The production of seed oysters involves the use of a chemical called cytochalasin B. Cytochalasin B has been shown to cause cancer in mice. Evaluate the production of triploid oysters for supermarkets and restaurants.