AQA GCSE Trilogy Biology Paper 2 Higher June 2019 question paper 8464/B/2H

Some students investigated the effect of drinking caffeine on reaction time. They used a drink containing 32.25 mg of caffeine per 100 cm³ This is the method used.

1. Divide the students into four groups, A, B, C and D.

2. Measure and record the reaction time of each student using the ruler-drop test.

3. Students in:

group A drink 200 cm³ of water

group B drink 200 cm³ of the caffeine drink

group C drink 400 cm³ of the caffeine drink

group D drink 600 cm³ of the caffeine drink.

4. Repeat step 2 after 15 minutes.

Describe how to do the ruler-drop test.

Table 1 shows the mass of caffeine taken in by each student.

Calculate value X.

Why did group A drink water instead of the caffeine drink?

Table 2 was used to convert the results of the ruler-drop test into reaction times.

Estimate the reaction time for a student who recorded a distance of 23 cm

Students calculated the decrease in their reaction time after the drink compared with before the drink. Figure 1 shows the results for each student.

Describe the effect of the mass of caffeine taken in on the decrease in reaction time.

For three students the decrease in reaction time was negative. Give the reason why the value was negative.

What is the range of results for group C ?

Suggest two variables that should have been controlled in this investigation.

Explain why the ruler-drop test does not involve a reflex action.

There has been a rapid increase in the percentage of carbon dioxide in the atmosphere since 1960.

Carbon dioxide is a greenhouse gas that contributes to global warming. Name one other greenhouse gas.

Global warming causes climate change. Give two effects of climate change.

Question 2 continues on page 10

Plants take in carbon dioxide from the atmosphere. Figure 2 shows part of the carbon cycle.

Describe how carbon from the atmosphere is cycled through living organisms.

Vectors are used in the process of genetic engineering. Which two statements are correct? Tick (✓) two boxes.

Scientists have genetically engineered a variety of wheat to be resistant to herbicides. The herbicide resistant variety of wheat will give a higher yield than the non-herbicide resistant variety. Explain why.

Give two examples of genetic engineering in use today. Do not refer to herbicide resistance in your answer.

Scientists working on the ‘Human Genome Project’ have now mapped the entire genetic code of humans. Explain one way this could be important for people in the future.

Animals have adaptations to survive in their environment. These adaptations may be structural, behavioural or functional.

Draw one line from each animal adaptation to the type of adaptation it is.

Animal adaptation Type of adaptation

Plants also have adaptations. There are more than 28 000 known species of orchid plants.

Many orchid plants:

• grow attached to other types of plants

• have brightly coloured flowers

• produce large quantities of pollen

• produce thousands of tiny, light seeds.

Describe how these adaptations help orchid plants to survive and compete.

A rare orchid has been found in the mountains in China. The orchid has pale yellow flowers. DNA analysis of the genome shows that it is an ancestral species. All other present day orchids evolved from this ancestral species millions of years ago.

One present day species has bright purple flowers. Describe how an orchid with bright purple flowers may have evolved from the ancestral species which has pale yellow flowers.

The DNA code determines the sequence of amino acids which are joined together to form a specific protein. Table 3 shows part of the amino acid sequence for the colour pigment protein in five orchid species. The rest of the amino acid sequence is the same for all the species.

ala = alanine gly = glycine isoleu = isoleucine leu = leucine tyr = tyrosine Suggest which orchid species is most closely related to the ancestral species. Give a reason for your answer.

Some students estimated the population of daisies in a school field. This is the method used.

1. Find a place where some daisies are growing.

2. Put the quadrat down.

3. Count and record the number of daisies in the quadrat.

4. Repeat steps 1–3 at four different places in the field.

5. Calculate the mean number of daisies per quadrat.

6. Use the data to estimate the total number of daisies in the field.

Which two improvements would increase the validity of this method? Tick (✓) two boxes.

With an improved method the students calculated the mean number of daisy plants to be 7.65 per quadrat. The students used a quadrat measuring 50 cm × 50 cm Figure 3 shows the school site and the dimensions of the school field.

Calculate the population of daisy plants on the school field. Give your answer in standard form to 2 significant figures.

The students noticed a very uneven distribution of daisy plants in the field. Explain how different biotic factors and abiotic factors could have caused an uneven distribution of daisy plants. Use Figure 3 on page 20.

This question is about homeostasis.

Define the term homeostasis.

Name the hormone released if the blood glucose concentration falls too low.

Two people were sent to a hospital to find out if they have diabetes. This is the method used at the hospital.

• Do not eat or drink after midnight. This is called fasting.

• Measure blood glucose concentration at 9.30 am

• Drink a glucose solution at 10.00 am

• Measure blood glucose concentration for the next 3 hours.

Figure 4 shows the results.

Person A and person B have diabetes.

Describe how Figure 4 shows that person B has diabetes. Use data from Figure 4.

Person A and person B had a test to measure the concentration of insulin in their blood when they were fasting. Table 4 shows the results.

Suggest which type of diabetes person A and person B have. Give a reason for each answer. Person A

Person B

Toxic hypoglycaemia syndrome (THS) has caused the deaths of hundreds of starving children in some tropical countries.

• The starving children have had nothing to eat all day.

• The starving children then eat many lychee fruits.

• The lychee fruits contain a molecule which stops an enzyme in the liver working.

• This enzyme normally converts stored fats into glucose.

Children who have eaten during the day are not affected by eating many lychee fruits.

Starving children may die from eating many lychee fruits but children who have eaten during the day are not affected. Explain why.