Practice Paper 2 (Edexcel IGCSE Science)

The diagram below shows a representation of the carbon cycle.

Explain how carbon is returned to the atmosphere at the stage labelled Y.

The diagram in part (a) is missing many details of the carbon cycle.

Label the diagram as follows to show where each of the processes occurs within the carbon cycle.

(i) Use a letter R to show where respiration occurs.

(ii) Use a letter P to show where photosynthesis occurs.

(iii) Use a letter F to show where feeding occurs.

Carbon from fossil fuels enters the atmosphere during combustion.

(i) Explain how this process contributes to rising average global temperatures.

(ii) Explain how cutting down trees during deforestation increases the problem described in part (i).

A student studies the organisms in a pond community.

Which of these is the correct description of a community?

The table shows the number of organisms per m² at different trophic levels in a pond community.

It also shows the total biomass of these organisms per m².

(i) Calculate the mean mass in g of a single primary consumer.

Give your answer in standard form.

(ii) Use the grid to draw a pyramid of biomass for the pond community.

The number of secondary consumers is low because energy transfer is not 100 % efficient.

(i) Explain why egestion is one reason why energy transfer is not 100 % efficient.

(ii) Give two other reasons why energy transfer is not 100 % efficient.

There is a general consensus amongst the scientific community that increased levels of carbon dioxide emissions, as a result of human activity, are causing global warming due to an enhanced greenhouse effect.

Explain how increases in the proportions of greenhouse gases in the atmosphere have led to global warming.

Global warming, and the climate change that it brings, have an overall detrimental effect on biodiversity and ecology in general.

Suggest and explain one effect of global warming that may be beneficial to an individual species.

The graph below shows the total greenhouse gas emissions from Europe and China from the years 1990 to 2019.

The emission data is given using the unit billion tonnes.

(i) Describe the data in the graph.

(ii) Give two reasons that could explain the trends shown in the graph.

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 0.214kg 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.

A scientist studies hair colour in mice.

Mice can have grey hair or white hair.

The hair colour is determined by a gene with two alleles.

In the first cross, a male mouse with white hair is mated with a female mouse with grey hair.

All the offspring have grey hair.

(i) State what is meant by the term gene.

(ii) State the phenotype coded for by the dominant allele.

A male mouse and a female mouse with grey hair were chosen from the offspring of the first cross. These mice are mated in a second cross.

Some of the offspring of this second cross has grey hair and some have white hair.

Use a genetic diagram to show the second cross.

You should give the genotypes of the parents and the gametes formed. You should also give the genotypes and ratio of phenotypes of the offspring.

The scientist concludes that a mouse with grey hair could have two possible genotypes.

Explain how the scientist could use a cross to determine the genotype of a mouse with grey hair.

Albino mice have white hair. These mice also have pink eyes as they do not have pigment in their irises.

They are also less likely to explore a new area when compared to mice with grey hair.

This is an example of one gene having many effects.

Describe how the genetic control of most phenotypic features differs from this example.

The diagram shows an insect-pollinated flower called a lily.

(i) Which of these is the name of structure P?

(ii) Which of these is the name of structure Q?

(iii) On which structure do pollen grains germinate?

Describe how the structures of P, Q and S would differ in a wind-pollinated flower.

Plants can also reproduce by asexual reproduction.

(i) Give one natural method that plants use to reproduce asexually.

(ii) Give one artificial method that a plant grower may use to reproduce a plant asexually.

(iii) Suggest why a plant grower may choose to reproduce a plant asexually rather than allowing the plant to reproduce sexually.

The image shows three different biological molecules.

Name the biological molecules represented by X, Y and Z.

Name one element found in all three of the biological molecules shown in part (a).

With reference to molecule Z from part (a):

(i) Outline the test used to identify the molecule in a sample of food.

(ii) Explain the effect of very high temperature on the shape of this molecule.

A group of scientists carried out a study to investigate the starch content of roots in a species of grass at four points throughout the year.

Their results can be seen in the graph below.

(i) Explain why the grass roots contain starch.

(ii) Explain how the starch found in the roots of grass species helps to support growth of the grasses.

(i) Calculate the percentage change in stored starch from January to October in the graph in part (b).

(ii) Suggest an explanation for the change calculated in part (i).

The diagram shows the position of some hormone producing glands in the female body.

Which of these structures is the adrenal gland?

The adrenal gland is an organ that secretes adrenaline.

State what is meant by the term organ.

Adrenaline is released into the blood when there is danger.

The list gives the effects of adrenaline on different parts of the body.

• dilates the pupil in the eye
• increases heart rate
• narrows small arteries in the intestine
• converts glycogen into glucose in the liver

Explain the advantages of these effects to a person in danger.