Edexcel GCSE Combined Science Paper 2: Biology 2 Higher November 2020 question paper 1SC0/2BH

Figure 1 shows the leaves and flowers of water lily plants (Nymphaea odorata) on a lake.

Water lilies have stomata on the upper surface of the leaves.

Explain why water lilies have no stomata on the lower surface of the leaves.

The white petals of the water lily flowers cannot photosynthesise.

Which structure in leaf cells is the site of photosynthesis?

Glucose is made by photosynthesis.

Glucose is converted to another sugar to be transported in the plant.

What is the name of this sugar?

Describe how this sugar is transported from the leaves to the flowers of the water lily.

Figure 2 shows water lilies growing in a lake in Europe.

One water lily plant was brought from America 10 years ago and planted in the lake shown in Figure 2.

Explain why this non‑indigenous plant now covers the whole surface of the lake.

A slide of potato cells was viewed using a light microscope.

Figure 3 is a drawing of the slide showing starch grains in the potato cells.

Calculate the mean number of starch grains in potato cells P, Q and R.

Which structures are found in plant cells but are not found in animal cells?

A scientist investigated how the length of starch grains in potatoes changed when the potatoes were stored in the dark.

Figure 4 shows a potato after being stored in the dark.

Figure 4

Three potatoes were used in the investigation.

The length of starch grains in potato 1 were measured at the start.

The length of starch grains in potato 2 were measured after 5 weeks in the dark.

The length of starch grains in potato 3 were measured after 10 weeks in the dark.

Figure 5 shows the results.

Calculate the percentage difference in the mean length of starch grains in potato 2 at 5 weeks and in potato 3 at 10 weeks.

State two variables the scientist should have controlled to improve this investigation.

The starch grains in the potatoes became smaller as the starch was converted into glucose.

State why the potatoes need glucose.

Describe how starch is broken down into glucose.

Trypsin is a protease enzyme used in the manufacture of food for babies.

Which food group is digested by trypsin?

The food is mashed before the trypsin is added.

Explain the advantage of mashing the food before adding the trypsin.

A manufacturer of baby food wanted to find out the optimum pH for trypsin.

Equal volumes of different pH solutions were placed in six separate test tubes.

5 cm³ of 1% trypsin solution was added to each test tube.

1.5 g of mashed food was placed in each test tube.

The time taken to digest the food was recorded.

State one other variable that should be controlled in this investigation.

State how this variable could be controlled.

The results are shown in Figure 6.

Describe the trends shown in this data.

At pH 4, the trypsin digested 1.5 g of mashed food at a rate of 0.8 g per minute.

Calculate the rate of digestion at pH 1.

Give your answer to one significant figure.

Explain the difference in the rate of reaction at pH 1 and the rate of reaction at pH 4.

Figure 7 shows the time taken for blood to clot at different temperatures.

Draw a graph to show the data in Figure 7.

Give two safety precautions that should be used when handling blood samples.

Which part of the blood causes blood to start clotting?

Give one advantage of a blood clot forming.

Explain how one structure of a vein helps the blood return to the heart.

Figure 8 shows the heart rate of person A and person B.

Person A does not do any regular exercise.

Person B has been running regularly for one year.

Both people rested for the first 6 minutes, then did the same high intensity exercise for the next 12 minutes, then rested.

Compare the heart rates of person A with the heart rates of person B.

The stroke volume for person B before exercising was 61 ml per beat.

Calculate the cardiac output for person B before exercising.

Give your answer in litres per minute.

_........ litres per minute

The cardiac output for person A during exercise was 5.5 litres per minute.

Explain why the heart rate for person A needed to be higher than the heart rate for person B during exercise.

Hyperthyroidism is caused by an overactive thyroid gland.

Figure 9 shows a person with a normal thyroid gland and a person with hyperthyroidism.

State one effect of hyperthyroidism on the thyroid gland.

The thyroid gland is part of the

Explain how negative feedback, involving the thyroid gland, controls metabolic rate.

*(c) Explain how hormones control the menstrual cycle.