IGCSEScienceEdexcelScience (Double Award) (Modular)Biology Unit 2Exam Questions5. Ecology & the EnvironmentHuman Influences on the Environment

Human Influences on the Environment (Edexcel IGCSE Science (Double Award) (Modular): Biology Unit 2): Exam Questions

Exam code: 4XSD1

1 hour7 questions
Easy
Medium
Hard
1a
1 mark

Which row of the table gives the combination of factors that would lead to an increased amount of human waste being produced?

+ means increasing       - means decreasing

 

Standard of Living

Population 

Life expectancy

A

+

+

+

B

-

+

+

C

-

-

+

D

-

-

-

    Choose your answer

    1b
    2 marks

    State two ways in which pollution can reduce biodiversity.

    How did you do?

    1c
    2 marks

    The boxes below show a number of pollutants and the ways that they affect ecosystems.

    Two columns of rectangular boxes. The left column lists three pollutants, from top to bottom: sulfur dioxide from burning fossil fuels, nitrates from overuse of fertiliser, and use of pesticides on crops. The right column lists three effects, from top to bottom: eutrophication, bioaccumulation, and acid rain. No lines have been drawn between the two columns.

    Draw a line between each pollutant and the effect that it creates.

    How did you do?

    1d
    2 marks

    Pesticide levels in the water of a lake were measured at a level of 877 parts per billion.

    The same pesticide was measured in the gills of a fish living in that lake and showed biomagnification by a factor of 9.75 million (9 750 000) times.

    Calculate the concentration of the pesticide in the fish's gills. Give your answer in standard form. 

    How did you do?

    1e
    1 mark

    Part (d) gives an example of biomagnification, in which the level of a dangerous compound gets higher at successive trophic levels. 

    Explain how biomagnification differs from bioaccumulation.

    How did you do?

    2a
    3 marks

    When raw sewage is released into a waterway it can lead to eutrophication. 

    The statements below list some of the stages of the process of eutrophication. 

    Complete the table by numbering the statements to put the stages into the correct order. 

    Stage of Eutrophication

    Order

    Algal bloom prevents sunlight from reaching aquatic plants. Water oxygen levels fall

     

    Excessive nutrients from fertilisers run-off from the land into the water

     

    Algae also show rapid growth

     

    Death of organisms requiring dissolved oxygen in water

     

    Decomposition rate increases. Aerobic respiration of decomposers reduces dissolved oxygen further

     

    Aquatic plants flourish, growing rapidly

     

    How did you do?

    2b
    2 marks

    Explain one other potential consequence of the release of raw sewage into a water system. 

    How did you do?

    2c
    3 marks

    One of the steps of eutrophication involves the decomposing microorganisms carrying out aerobic respiration and depleting the quantity of dissolved oxygen in the water.

    (i) Add the correct words in the gaps in the space below to complete the word equation of aerobic respiration.

    ............................ + oxygen → ............................ + ............................

    [2]

    (ii) Respiration provides energy for the cell processes carried out by these decomposers.

    Name one of these processes that is directly linked to how the decomposers get their nutrition.

    [1]

    How did you do?

    3a
    3 marks

    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.

    How did you do?

    3b
    1 mark

    State how sulfur dioxide pollution can be reduced.

    How did you do?

    3c
    4 marks

    Another chemical that contributes to air pollution is carbon monoxide.

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

    [2]

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

    [2]

    How did you do?

    1a
    4 marks

    Farmers may add chemical fertilisers to their soil.

    Explain how chemical fertilisers can increase crop yield.

    How did you do?

    1b
    4 marks

    These fertilisers may leak into rivers.

    A scientist measures the oxygen content of water in two different locations of the same river during the month of April.

    A curved river drawn as two arcs running from left to right. Location A is labelled at the left-hand end of the river and location B at the right-hand end. An arrow above the river, labelled direction of river flow, points from left to right, so water flows from location A to location B. A grey rectangle labelled farmer's field lies beside the river, between location A and location B.

    In location A he finds that the mean dissolved oxygen was 6 mg per litre and at location B he finds that the mean dissolved oxygen was 3 mg per litre.

    He concludes that the use of fertiliser in the field has affected the oxygen content of the river.

    Discuss his conclusion.

    How did you do?

    1c
    1 mark

    Some farmers use alternative substances to chemical fertilisers.

    Suggest one alternative substance that a farmer may use.

    How did you do?

    2a
    2 marks

    The diagram shows a river and the location of a fertiliser factory. The arrows indicate the direction of the flow of the river.

    Line diagram of a meandering river. Arrows at the top of the diagram and at the bottom right show that the river flows from the top of the diagram towards the bottom right. A fertiliser factory stands on the left bank, part way along the river's course. Site A is labelled on a bend upstream of the factory and site B is labelled on a bend downstream of the factory

    A scientist recorded the nitrate concentrations of the water at site A and site B. Her results are shown in the table.

    Site

    Nitrate concentration / mg per dm3

    Sample 1

    Sample 2

    Sample 3

    Mean

    A

    17

    25

    18

    20

    B

    49

    64

    58

    Calculate the mean nitrate concentration found at site B.

    How did you do?

    2b
    4 marks

    The scientist observed algae and some dead fish in the river at site B. These were not present at site A.

    Give an explanation for these observations.

    How did you do?

    2c
    4 marks

    Scientists carried out another test and found higher than normal levels of sulfuric acid dissolved in the water in the stream at both sites. 

    Explain a series of events that could have led to sulfuric acid washing into the river. 

    How did you do?

    1a
    4 marks

    The table below gives data about how the carbon dioxide (CO2) concentration of the earth's atmosphere has changed over time.

    Year

    CO2 concentration in parts per million

    1800

    282

    1900

    295

    1950

    310

    2000

    370

    2020

    410

    2022

    420

    Plot the data from the table on the graph paper provided below.

    Blank graph paper, printed as a grid of small squares grouped into larger squares, with no axes, scales or labels printed on it

    How did you do?

    1b
    3 marks

    Explain why carbon dioxide concentrations in the atmosphere are changing.

    How did you do?

    1c
    2 marks

    In 2022 a climate activist claimed that, to arrest global warming, the atmospheric CO2 level should be brought back to the level of the year 1900.

    Using the data from the table in part (a), calculate the percentage decrease that the climate activist claims would be needed to return the atmospheric CO2 level to its 1900 level. 

    How did you do?

    2a
    2 marks

    When fossil fuels are burned sulfur dioxide gas (SO2) can also be released into the atmosphere. 

    Flue gases from the burning process can be captured and desulfurised, a process which traps the flue gases and reacts with the sulfur dioxide with calcium hydroxide.

    A further step results in the formation of calcium sulfate which is a major component of plasterboard used in the building industry. 

    Ca(OH)2(s) + SO2(g) → CaSO3(s) + H2O(l)

    Apart from supplying the building industry, explain one benefit of the process of flue gas desulfurisation. 

    How did you do?

    2b
    3 marks

    Describe the potential consequences for living organisms of failing to carry out flue gas desulfurisation. 

    How did you do?

    2c
    5 marks

    There are currently two main ways in which household rubbish is disposed of by local authorities in the UK.

    These are:

    • Landfill: rubbish is buried underground

    • Incineration: rubbish is burned at 1000 °C

    The table below outlines some of the features of both methods. 

    Landfill

    Incineration

    Traditional, trusted

    A newer method

    Needs a large hole in the ground, e.g. a disused quarry

    Involves a high-tech incineration plant

    Generates CO2 and methane as organic waste decays

    Generates a lot of CO2

    Causes odours and insect/rat infestations

    Clean-burning can mean that few pollutants are emitted to the atmosphere/rivers

    Requires waste to be transported a long way, even exported

    Generates heat and electricity for the local grid

    Suitable sites are running out

    Unpopular with local people

    Toxins can be leached from landfill sites when water runs through a site

    Can be set up in all localities

    Use the data in the table and your knowledge of waste treatment to evaluate both methods of waste disposal. 

    How did you do?