Ecosystems, Nutrient Cycles & Human Impact on the Environment (WJEC GCSE Biology): Exam Questions

Image 5 shows the carbon cycle.

Image 5

Use Image 5 to describe the carbon cycle.

Your answer should include:

• the names of the processes represented by the arrows W, X, Y and Z

• the names of two types of decomposers.

Image 7 shows a pyramid of numbers in African grassland.

Image 7

(i) State the producer in this pyramid.

[1]

(ii) Underline two terms from the list below that can be used to describe the zebra.

[1]

Producer

Secondary consumer

Carnivore

Herbivore

Primary consumer

(iii) Write the food chain that is represented by the pyramid of numbers in Image 7.

[1]

(iv) State the source of energy for a food chain.

[1]

(v) State one reason why not all of the energy is passed from one stage of the food chain to the next.

[1]

(vi) Suggest why this pyramid of numbers is not pyramid-shaped.

[1]

(vii) In the space below draw a labelled pyramid of biomass for the organisms shown in Image 7. Your pyramid of biomass does not need to be to scale.

[2]

Image 1.1 shows a food web from an area of grassland.

Image 1.1

(i) Use Image 1.1 to state the organisms which are present in the highest numbers.

[1]

(ii) Name the third stage (tertiary) consumers shown in the food web in Image 1.1.

Give the reason for your choice.

[2]

Name ........................................................................

Reason ......................................................................

One food chain from the food web is shown below. The images are not to scale.

Table 1.2 shows the results of an investigation of the organisms in this food chain in the area of grassland habitat.

Table 1.2

(i) Complete Table 1.2 by calculating the total biomass for each of the organisms in this food chain. One has been done for you.

[2]

Space for working.

(ii) Use Table 1.2 to complete the pyramid of numbers in Image 1.3 by writing the names of the organisms in this food chain and the numbers of each.

[1]

Image 1.3

(iii) State one way in which energy can be lost from a food chain and explain how this loss of energy is shown in the pyramid.

[2]

Sea anemones are animals which are often found in rock pools along the seashore. Image 5.1 shows a sea anemone.

Image 5.1

On warm sunny days:
• the water temperature in rock pools increases.
• evaporation occurs, so the concentration of salts in the water increases
• the water becomes acidic (pH lower than 7).
• concentration of salt in sea water is HIGHER than anemone cells.
• concentration of water in sea water is LOWER than anemone cells

Image 5.2 shows a rock pool at the end of a warm day.

Image 5.2

Fact file – Conditions required for sea anemones to survive.

Table 5.3 shows how the sea water temperature affects its oxygen concentration.

Table 5.3

Use the information to answer the following questions.

(i) State how the oxygen concentration of sea water changes when the temperature increases. [1]

(ii) Calculate the mean change in oxygen concentration per degree when the temperature rises from 10ºC to 30ºC. [2]

Mean change in oxygen concentration per degree = ............................................... mg/dm³

The statements in Table 5.4 refer to conditions in a rock pool at the end of a warm, sunny day when the sea water temperature was 24ºC. Write true or false for each statement. [4]

Table 5.4

The increasing level of carbon dioxide in the air is causing global warming. Image 7.1 shows one effect of global warming

Image 7.1

Image 7.2 shows part of the carbon cycle.

Image 7.2

Explain how the processes of photosynthesis, respiration and combustion each affect global warming. Suggest how humans could try to reduce the levels of carbon dioxide in the air.

Image 9.1 shows chickens in two different farming systems.

Image 9.1

In 1950 chicken was an expensive food and most adults in the UK, on average, ate only 1100g each year. By 2000 they ate 25kg per year as intensive farming had made chicken much cheaper.

In intensive farming, large numbers of chickens are reared indoors. Environmental conditions and food supply are constantly controlled. The chickens grow faster than free-range chickens and use less energy as their movement is restricted.

The farmer can monitor the chickens more easily than on a free-range farm. Much less land is used and labour costs are lower but larger amounts of concentrated waste are produced.

(i) Use the information given to calculate the increase in mass in the annual consumption of chicken for a family of four adults in the UK between 1950 and 2000.

[2]

Increase in mass = ......................................................... kg/family / year

During an investigation, the growth of chickens from different farm systems was compared. The results are shown in Graph 9.2 and Tables 9.3 and 9.4.

Graph 9.2

Table 9.3

Organ mass in chickens at six weeks

Table 9.4

Bone quality in chickens at six weeks

(ii) Use Graph 9.2 to calculate the difference in the body muscle mass at 5 weeks between intensively farmed chicken and a free–range chicken.

[1]

Difference = ......................................................... g

(i) Use the information on page 23 to suggest one advantage to farmers of farming chickens intensively.

[1]

(ii) State one feature of intensive farming which is an environmental disadvantage.

[1]

Some groups of people have ethical objections to intensive farming because of animal welfare concerns.

Using the information in Tables 9.3 and 9.4, state three features of intensive farming which support this point of view.

Image 7 shows the total amount of energy entering a grassland habitat in kilojoules per square metre during a year. The transfer of energy in a food chain is shown, as well as the energy that is lost from it as heat.

Image 7

(i) State the name of the stage in Image 7 which represents the herbivores.

[1]

(ii) State the name of one type of decomposer.

[1]

(i) Use the data from Image 7 to calculate the percentage of energy transferred from the first stage consumer to the second stage consumer. Give your answer to three significant figures.

[2]

Percentage of energy transferred = .........................................................

(ii) Suggest why the food chain shown in Image 7 would be unable to support a fourth stage consumer.

[1]

In the space below, use a ruler to draw a labelled pyramid of biomass to represent the food chain shown in Image 7. The pyramid does not need to be to scale.

State which process is responsible for the heat loss in Image 7.

Graph 8 shows the percentage change in global food production, human population and the land used for food production between 1960 and 2014.

Graph 8

Use the information in Graph 8 to state one conclusion about the efficiency of food production. Explain your answer.

Use your knowledge of the nitrogen cycle to explain how farmers can increase the nitrogen available to their crops and so increase their yield. Diagrams will not gain credit.

Image 1.1 shows a marine food web.

Image 1.1

Images are not to scale.

From the food web in Image 1.1, state the name of:

(i) the producer;

[1]

(ii) the tertiary (third-stage) consumer.

[1]

State what the arrows in the food web in Image 1.1 represent.

A disease caused the number of squid to decrease. Suggest what would happen to the numbers of penguins and crabs by underlining the correct word in each of the following sentences.

(i) The number of penguins would (increase / decrease).

[1]

(ii) The number of crabs would (increase / decrease).

[1]

The amount of pollution in water can be determined by measuring oxygen levels, pH levels or by using indicator species. Polluted water will have low oxygen levels, as bacteria use up oxygen. The water will become more acidic.

Air pollution can be assessed using indicator species, such as lichens. Lichens are organisms that consist of fungi and algae living together. Lichens can grow on tree bark and rocks. There are many species of lichen which can be grouped into three main types: bushy, leafy and crusty. The number of types of lichens present can indicate the level of air pollution.

• Bushy lichens can only survive in unpolluted air.

• Leafy lichens can survive a small amount of air pollution.

• Crusty lichens can survive in more polluted air.

• The more types of lichen growing in an area, the lower the level of air pollution.

Use the information above to complete Table 5.1 by writing true or false next to each statement.

[4]

Table 5.1

(i) In 2019, a study rated the air quality in the centre of Cardiff as being worse than the centre of London.

Image 5.2 shows the three main types of lichen.

In Image 5.2 circle the letter (A, B, C) of the type of lichen you may expect to find growing in Cardiff city centre if there was a lot of air pollution present.

[1]

Image 5.2

A scientist counted the number of species of lichens growing at different distances from the centre of Cardiff. Her results are shown in Table 5.3.

Table 5.3

(ii) Complete Table 5.3 by estimating the number of species of lichen likely to be found 5km from Cardiff centre.

[1]

(iii) State the independent and dependent variables in this investigation.

[2]

Independent variable ..................................................................................................

Dependent variable ..................................................................................................

(iv) I. State the relationship between the number of lichen species and the distance from the centre of Cardiff.

[1]

II. Use the information given to explain the relationship between the number of species of lichen and the distance from the centre of Cardiff.

[2]

(v) State how the scientist could improve her confidence in these results.

[1]

Nitrate Vulnerable Zones (NVZ) are areas where nitrate concentrations are a risk to human health, or harmful to the aquatic environment.

Llangorse lake is the largest natural lake in south Wales. Approximately two-thirds of the surrounding land is used for intensive farming. Natural Resources Wales (NRW) has calculated that 99% of the nitrate found in Llangorse lake comes from intensive farming.

Table 6.1 is used by NRW to estimate the risk from nitrate levels in water.

Table 6.1

Between December 2011 and July 2014, water samples were taken from Llangorse lake and the nitrate concentration analysed.

The results are shown in Graph 6.2.

Graph 6.2

Algal blooms were observed in Llangorse lake between April and October for each year shown in Graph 6.2.

(i) Using the information above, state the risk level for nitrates in Llangorse lake in January 2013.

[1]

(ii) Describe the annual trend common to all years shown in Graph 6.2.

[2]

(iii) Suggest a possible explanation for the common annual decrease in the nitrate levels in Llangorse lake.

[2]

Explain how intensive farming leads to the formation of algal blooms and how these algal blooms can be harmful to aquatic animals.

The United Nations Minamata Convention on Mercury is a global treaty to protect human health and the environment from the toxic effects of the heavy metal mercury.

In 2010, combustion of fossil fuels by industrial processes produced 24% of the total global emissions of mercury. Image 8.1 shows how this mercury is cycled in the environment.

Image 8.1

(i) Calculate the percentage increase in mercury from the plankton to humans. Give your answer to two significant figures.

[3]

Percentage increase = ........................................................

(ii) Using Image 8.1 and your own knowledge, explain how the mercury released during the combustion of fossil fuels by industrial processes becomes harmful to humans.

[3]

Apart from reducing mercury pollution, explain how reducing the combustion of fossil fuels can benefit the environment.