Practice Paper 1 (Edexcel IGCSE Science)

The diagram shows a cycle found in ecosystems.

Give the name of the cycle.

(i) In the image in part (a), which process is represented by the letter W?

(ii) In the image in part (a), which process is represented by the letter X?

Name a group of organisms that is responsible for decomposition.

Carbon dioxide is released into the atmosphere by the decomposition of organic material.

The rate of this decomposition depends on a number of factors.

Design an investigation to find out if changing the pH of organic material affects the rate of decomposition.

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

The diagram shows a food chain in the Antarctic ocean.

(i) Which term describes the trophic level of the krill?

(ii) Draw a labelled pyramid of biomass to represent this food chain.

The microscopic plants float in seawater, but also grow on the lower surface of ice.

The krill feed on the microscopic plants.

They remove microscopic plants from the lower surface of the ice at a rate of 1.6 cm² per second.

Calculate the time taken for the krill to remove microscopic plants from one square metre of ice.

Give your answer in minutes.

A student investigates the rate that krill feeding removes microscopic plants floating in seawater.

Suggest how the student could do this investigation in a laboratory.

Krill obtain most of their food from microscopic plants growing on the lower surface of ice.

Explain how global warming could affect the whale population in the Antarctic ocean.

The air around us can contain a lot of chemicals that can be harmful to human health.

Explain the biological consequences of air pollution by sulfur dioxide.

State how sulfur dioxide pollution can be reduced.

Another chemical that contributes to air pollution is carbon monoxide.

(i) State whether carbon monoxide is a greenhouse gas. Explain your answer.

(ii) Explain why carbon monoxide is a harmful air pollutant.

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.

Devise 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.

Cleft chin is a phenotype believed to be controlled by a single gene that has two alleles.

The dominant allele, N, codes for cleft chin and the recessive, n, allele codes for the absence of the cleft chin.

With reference to the example of cleft chin, state what is meant by the following terms

(i) Phenotype

(ii) Gene

(iii) Allele

A woman with a cleft chin has a child with a man who also has a cleft chin. The child does not have a cleft chin.

(i) Use a genetic diagram to show the genotypes of the parents, the gametes they can produce and all the possible genotypes and phenotypes of their children.

(ii) The parents then have a second child.

Calculate the probability that this child will be female and not have a cleft chin.

(iii) Sometimes a cleft chin does not develop even if the individual inherits the dominant allele.

Suggest what might cause this.

Most inherited conditions are not controlled by a single gene, but by many genes.

Describe how a scientist could distinguish between a genetic condition in rats controlled by a single gene and one controlled by many genes.

Scientists investigate the effect of salt (NaCl) concentration on the germination of maize seeds.

Batches of seeds are watered with different concentrations of salt solution.

They count the number of seeds that germinate in each batch 12 days after sowing. They then determined the percentage germination.

(i) Describe how the scientists could tell if a maize seed had germinated.

(ii) The scientists measured the germination after 12 days.

State two other abiotic variables that the scientists need to control in their investigation.

The table shows the scientists’ results.

(i) Plot a line graph to show the effect of the concentration of the salt solution on germination.

Use a ruler to join your points with straight lines.

(ii) Explain the effect of increasing the concentration of the salt solution on germination.

As plants grow, they produce roots and stems.

(i) Compare the responses of roots and stems to gravity.

(ii) Compare the responses of roots and stems to light.