Food Production (Edexcel IGCSE Science (Double Award) (Modular): Biology Unit 2): Exam Questions

Mycoprotein is a protein produced by fungi that can be made into meat substitutes.

Large amounts of fungus are grown in fermenters to produce the mycoprotein.

The diagram shows a typical mycoprotein fermenter.

(i) Explain why air is bubbled into the fermenter.

[2]

(ii) Explain why the fermenter is cleaned using steam before the fungus and nutrients are added.

[2]

A scientist investigates the production of mycoprotein by a genetically modified (GM) fungus and a non-genetically modified fungus (non-GM).

The scientist claims that the GM fungus will be better for large-scale production of mycoprotein.

The scientist measures the mass of mycoprotein produced by the fungi in fermenters for 30 days.

The table shows the scientist’s results.

(i) Plot a line graph to show how the mass of mycoprotein changes over the 30 days for each type of fungus.

Use a ruler to join the points with straight lines.

[5]

(ii) The scientist claims that the GM fungus will be better for large-scale production of mycoprotein than the non-GM fungus.

Comment on the scientist’s claim.

[2]

(iii) The table shows the nutritional composition of mycoprotein and the nutritional composition of lamb.

Discuss whether eating mycoprotein is more healthy than eating lamb for a growing human.

[5]

Scientists carry out an experiment to see if reducing the availability of oxygen affects the production of yoghurt.

They use increasing acidity as a measure of yoghurt production.

They record the acidity of two cultures, one with a reduced oxygen level and one with a normal oxygen level, over 210 minutes.

The table shows their results.

Explain why increasing acidity can be used as a measure of yoghurt production.

Give one abiotic variable that the scientists should control in their experiment.

(i) Plot a line graph to show how the percentage acidity changes over the period of 210 minutes for the reduced oxygen level and for the normal oxygen level.

Use a ruler to join the points with straight lines.

[5]

(ii) Explain why the changes in percentage acidity are different in the reduced oxygen level and in the normal oxygen level cultures.

[2]

A balanced diet contains the correct proportion of vitamins.

The table lists the functions of some vitamins.

Complete the table by stating the correct vitamins.

The first one has been done for you.

Yeast is used to make bread.

A student investigates the effect of vitamin C on the growth of yeast cells.

This is his method.

• Put 0.50 g of yeast into a flask containing 200 cm³ of glucose solution and add 0.10 g of vitamin C.

• Put 0.50 g of yeast into another flask containing 200 cm³ of glucose solution without vitamin C.

• Measure the dry mass of yeast in each flask after 30 hours

The table shows the student’s results.

(i) The student calculates that the mean rate of yeast growth with vitamin C is 0.22 g per hour.

Calculate the mean rate of yeast growth without vitamin C.

Give your answer in g per hour.

[2]

(ii) Suggest how to find the dry mass of yeast in each flask.

[2]

(iii) State the dependent variable in this investigation.

[1]

(iv) The method gives some variables that the student controlled.

Justify two other variables the student should control.

[4]

The diagram shows a yeast cell.

Which of these is correct for this yeast cell?

Which type of organism is a yeast cell?

Scientists use genetically modified (GM) yeast to produce biofuel.

The yeast uses the glucose in respiration to produce ethanol.

Which of these equations shows the respiration in the yeast?

Biofuel is made from ethanol.

Scientists use genetically modified (GM) yeast to produce biofuel.

The GM yeast contains an enzyme that digests plant cell walls to produce glucose.

The yeast uses the glucose in respiration to produce ethanol.

(i) Name an enzyme used by scientists to genetically modify the yeast.

[1]

(ii) The GM yeast is a recombinant strain.

State what is meant by the term recombinant.

[1]

(iii) Suggest why biofuel produced using glucose from plants could reduce global warming.

[2]

The graph shows the mass of ethanol produced by GM yeast and by normal yeast over a period of 3 days.

(i) Calculate the percentage increase in the mass of ethanol produced by GM yeast compared to normal yeast after 1 day.

[2]

(ii) Give two reasons why the rate of ethanol production decreases after 1 day.

[2]

Farmers can keep their animals indoors or outdoors.

A student uses this apparatus to compare the heat loss from animals kept indoors and outdoors.

He uses a covered beaker to represent animals indoors and an uncovered beaker to represent animals outdoors.

This is the student’s method.

• Pour 200 cm³ of hot water into each beaker

• Measure the temperature of the water in each beaker

• Cover one beaker with a cardboard box

• Measure the temperature of the water in each beaker after 30 minutes

The student repeats the investigation six times and calculates the mean temperature of the water for each beaker.

The table shows the student’s results.

Give the dependent variable in this investigation.

Give one reason why the student uses the same volume of water in each beaker.

Calculate the difference between the percentage decrease in temperature for the uncovered beaker and the percentage decrease in temperature for the covered beaker.

The student concludes that it is better for farmers to keep their animals indoors.

Discuss this conclusion. 

Describe how the student could modify his investigation to find out if an animal’s body size affects heat loss.

The table shows data on crops grown and pesticide used in Norway in 2011.

State what is meant by the term pesticide.

Determine which crop had the largest area sprayed with herbicide.

Show your working.

Suggest why spring and winter wheat have different percentages of insecticide applied to them.

Discuss the different combinations of pesticides applied to fruit and cereal crops.

Explain an alternative to insecticide that a farmer could use.

Bread can be produced from flour using yeast.

Design an investigation to find out if changing the starch content of the flour causes the bread to expand more.

Your answer should include experimental details and be written in full sentences.

Farmers sometimes use biological control to reduce the damage to their crops caused by pests such as insects.

Which of these is an advantage of using biological control over chemical control?

Aphids are tiny insects that have very sharp mouthparts. They push these mouthparts into the phloem found in stems. They then feed on the phloem contents.

Shipher Wu and Gee-way Lin, National Taiwan University, CC BY 2.5 <https://creativecommons.org/licenses/by/2.5>, via Wikimedia Commons

(i) Name two substances the aphids obtain from the phloem.

[2]

(ii) Explain how aphids feeding from the phloem of crop plants can lead to a reduction in yield.

[4]

Silverflies and hoverflies are two species of insect whose larvae feed on aphids.

Scientists investigate the feeding behaviour of these species in a laboratory experiment.

This is the scientists’ method.

• Place a single silverfly in a container

• Place a single hoverfly in a separate container

• Keep the containers at 12 °C

• Put 30 aphids in each container

• Count the number of aphids consumed each day for several days

• Determine the mean number of aphids consumed per day

The scientists repeat the method at two higher temperatures.

The graph shows the scientists’ results.

The scientists conclude that the hoverfly is the most effective biological control agent for aphids.

Discuss the scientists' conclusion, referring to information in the graph and the scientists' method in your answer.

In some countries, snails are farmed as a source of protein.

The image below shows a snail.

A scientist investigates the effect of temperature on the growth of snails.

The scientist measures the mean (average) shell height of groups of snails kept at three different temperatures for 24 weeks.

The table shows the scientist’s results.

(i) Plot a line graph to show how the mean shell height increases with time for each temperature.

Use a ruler to join the points with straight lines.

[5]

(ii) Explain the effect of temperature on the growth of snails in this investigation.

[3]

(iii) State the dependent variable in the investigation.

[1]

(iv) State how the scientist made sure their results were reliable.

[1]

Assimilation efficiency is the percentage of food that is eaten and not egested as faeces.

Assimilation efficiency is calculated using this formula.

$\text{assimulation efficiency}(\%)=\left(\frac{\text{mass of food eaten}-\text{mass of faeces egested}}{\text{mass of food eaten}}\right)\times 100$

(i) A snail eats 1.2 g of food and produces 0.30 g of faeces.

Calculate the assimilation efficiency of this snail.

[2]

(ii) Explain why the assimilation efficiency of a primary consumer is less than the assimilation efficiency of a secondary consumer.

[2]

The production efficiency of an animal is the percentage of assimilated food that is made into new biomass.

The table shows the production efficiency of a mammal and a snail, both of which are primary consumers.

Suggest why there is a difference in the production efficiency of the mammal and the snail.