The Organism in the Environment (Edexcel IGCSE Science (Double Award) (Modular): Biology Unit 2): Exam Questions

Lichens are organisms that grow well on stone walls in unpolluted air.

Lichens grow less well in polluted air.

Car exhaust fumes contain sulfur dioxide that pollutes air.

A scientist investigates the effect of pollution by cars in a city.

This is her method.

• Measure the percentage area of a stone wall in the city centre covered by lichen

• Repeat this measurement at different distances from the city centre

The table shows her results.

Explain the results shown in the table.

Describe a method to measure the percentage of a stone wall covered by lichen.

Adding water to a powder called sodium metabisulphite will release sulfur dioxide gas.

Design a laboratory investigation to find out the effect of sulfur dioxide gas on the heat released by germinating seeds.

Include experimental details in your answer and write in full sentences.

The table gives some examples of biological processes.

Complete the table by giving the name of each process.

The first one has been done for you.

Zinc is poisonous to many plants and can affect natural selection.

A scientist investigates the ability of one grass species to survive at different distances from a zinc mine.

The scientist uses a sampling method to measure the percentage cover of this grass species at different distances from the zinc mine.

The graph shows the scientist’s results.

(i) The zinc concentration in soil is higher near the zinc mine than it is further from the zinc mine.

Explain how natural selection could be responsible for the results shown in the graph between 0 and 100 metres.

[4]

(ii) Describe a method the scientist could use to compare the population size of the grass species at 50 metres and 100 metres from the mine.

[4]

A scientist uses this method to investigate the effect of water quality on the growth of fish.

• fill a pond with filtered water

• fill another pond with unfiltered water

• place the same mass of fish of the same species in each pond

• determine the increase in total mass of fish in each pond after 180 days

The graph shows the scientist’s results.

The mean rate of increase in total mass of the fish in the filtered water is 0.214 kg per day.

Calculate the difference between the mean rate of increase in the total mass of the fish in filtered and unfiltered water.

Unfiltered water contains more bacteria.

Explain why unfiltered water containing more bacteria affects the growth of fish.

Give one biotic variable the scientist controlled in the investigation.

Give a method the scientist could use to control interspecific predation in the ponds.

Deforestation is the cutting down of trees.

After deforestation, many dead leaves are left on the forest floor.

A student investigates the decomposition of these leaves.

This is her method.

• Collect four samples of dead leaves each with a mass of 6.0 kg

• Label the samples P, Q, R and S

• Cut sample P into small pieces and keep at 10 °C

• Cut sample Q into small pieces and keep at 20 °C

• Do not cut sample R and keep it at 10 °C

• Do not cut sample S and keep it at 20 °C

• Measure the mass of each sample after three months

The graph shows her results.

Explain the results obtained by the student.

Calculate the difference between the rate of decomposition in sample P and the rate of decomposition in sample Q.

Give your answer in kg per month.

The student needs to control biotic variables in her investigation.

Give two biotic variables she should control.