Effects of humans on ecosystems

The graph illustrates the concentration of dissolved oxygen at various points along a river. At which point is sewage discharged into the river?

May/June 2015

Which row identifies a cause and an effect of eutrophication?

May/June 2015

A farmer is cultivating wheat in a field. The farmer applies insecticides to eliminate insect pests and chemicals to remove weeds from the field. Which statements about this field are correct?

May/June 2016

Which greenhouse gas comes from factory chimneys and is produced by herbivores?

May/June 2016

Which two air pollutants are responsible for acid rain?

May/June 2018

A large number of the world’s main rivers are dammed to regulate water flow. Which result of this would be beneficial to humans in the long term?

May/June 2019

The following are some consequences of deforestation: 1 fewer animal habitats; 2 reduced uptake of carbon dioxide during photosynthesis; 3 burning that releases gases into the atmosphere; 4 soil erosion and the loss of minerals needed for plant growth. Which two consequences are most likely to lead to global warming?

May/June 2019

Which human activity will contribute most to global warming?

May/June 2021

Hardwood trees in tropical rainforests are often cut down for timber. After this, one fast-growing crop, such as palm oil, is cultivated on that same area of land. What effect will clearing the rainforest have on the environment?

May/June 2021

Which row identifies factors that could lead to famine?

May/June 2021

What rises over the long term because of tropical deforestation?

May/June 2022

What rises over the long term because of tropical deforestation?

May/June 2022

Which human activity is most likely to make the greatest contribution to global warming?

May/June 2023

Run-off from fields that have had nitrogen-containing fertilisers applied may cause fish to die in rivers. Which sequence of events explains what happens when fish die because of water pollution by nitrogen-containing fertilisers?

May/June 2023

Parts of tropical rainforests are frequently felled and cleared. Once the trees have been cut down, the land is usually set on fire. What are the effects of this activity?

May/June 2023

The diagrams illustrate how rain is affected when it falls on an area of forested land both before and after houses are constructed. Before houses are built, rainfall is $100\%$, with transpiration at $40\%$, surface runoff at $10\%$ and groundwater at $50\%$. After houses are built, rainfall is $100\%$, transpiration at $25\%$, groundwater at $32\%$ and surface runoff $?\%$. What is the difference in the percentage of surface runoff before and after the houses are built?

May/June 2024

The graph plots the oxygen concentration in a river at stations $1$ to $5$, with each station $100\,\text{m}$ apart. A sewage outflow is located just after station $1$. At which stations are the concentrations of organic matter the lowest?

May/June 2024

The cutting down of tropical rainforest trees has several effects. Which effect could result in global warming?

May/June 2024

The concentration of dissolved oxygen in river water is recorded at equal intervals along the length of the river. Some untreated sewage is accidentally discharged into the river. Which graph shows how this pollution affects the dissolved oxygen in the water?

May/June 2024

Calculate the estimated total mass of plastic pollution that entered the ocean in 2020.

May/June 2024

Untreated sewage has nitrates and phosphates in it. What happens in the lake if untreated sewage is discharged into it?

May/June 2025

DDT is an insecticide and it is damaging to living organisms. Because it is not excreted, it accumulates inside the cells of living organisms. The diagram illustrates the route followed by DDT as it enters a lake. Dissolved in water 3 taken up by aquatic plants 3 eaten by herbivorous fish 3 eaten by carnivorous fish 3 eaten by fish-eating birds Which organisms would be harmed most by the DDT?

May/June 2025

These statements outline the process of eutrophication, which can occur when excess nitrogen fertiliser washes from fields into streams. They are not arranged in the right sequence. 1. Bacteria decay dead plants and use up oxygen. 2. Animals die or leave the area. 3. Light cannot reach aquatic plants. 4. The growth rate of algae increases. 5. Aquatic plants die. In which order should these statements be arranged?

May/June 2025

Which graph illustrates the changes that happen in a river after sewage pollution has entered it?

Oct/Nov 2015

Which factor would be least likely to lead to famine?

Oct/Nov 2015

An ocean has been contaminated by an oil spill. What would be least likely to increase the rate at which microorganisms break down the oil?

Oct/Nov 2015

Some consequences of deforestation are given below. 1 reduced uptake of carbon dioxide from the atmosphere 2 desertification 3 carbon released from soil and rotting wood through the action of microorganisms 4 dry soil 5 flooding, landslides and soil erosion Which of these consequences help to cause climate change?

Oct/Nov 2015

Fig. 5.1 illustrates several human activities that have an impact on the environment.

Oct/Nov 2015

Which of the following, after being disposed of, affects a river ecosystem for the briefest period of time?

Oct/Nov 2016

For what reason does the oxygen concentration in a river fall after sewage is discharged into it?

Oct/Nov 2016

The diagram illustrates several ways that human activities can impact the environment. Which activity is most likely to cause acid rain?

Oct/Nov 2017

Which human activity is likely to make the greatest contribution to global warming?

Oct/Nov 2018

During the last few years, many major rivers in different regions of the world have become more acidic. What has led to this change?

Oct/Nov 2018

Why are insecticides sometimes considered pollutants?

Oct/Nov 2018

The diagram indicates where a number of features are positioned beside a river that begins in the mountains and flows to the ocean.

Oct/Nov 2018

The graph illustrates how the percentage of carbon dioxide in the atmosphere has altered since 1700.

Oct/Nov 2018

Sewage is discharged into a river. Which curve shows the oxygen concentration in the river?

Oct/Nov 2019

The diagram illustrates the sources of a pollutant type that enters an ocean bay. What identifies the pollutant type?

Oct/Nov 2019

Describe the ways in which human activity may damage the ecosystem of a tropical rainforest.

Oct/Nov 2019

Which property would be unwanted in an insecticide?

Oct/Nov 2020

Which characteristic would be unwanted in an insecticide?

Oct/Nov 2020

Atmospheric air is made up of several gases.

Oct/Nov 2020

Which gas is involved in causing acid rain?

Oct/Nov 2021

The table presents the source and the effect of four air pollutants. What are the four pollutants?

Oct/Nov 2021

Costa Rica is a relatively small nation, occupying about $0.03\%$ of the Earth’s surface. Roughly $5\%$ of the planet’s plant and animal species are present in Costa Rica.

Oct/Nov 2021

The graph illustrates the dissolved oxygen concentration at various locations along a river. At which point is sewage discharged into the river?

Oct/Nov 2022

The graph illustrates the concentration of dissolved oxygen at various positions along a river. At which point is sewage discharged into the river?

Oct/Nov 2022

A team of scientists studied the total mass of carbon dioxide released when animals and plants are reared on farms and then eaten by humans as food.

Oct/Nov 2022

The list below shows some changes that may take place in a lake polluted with nitrogen-containing fertiliser. In what order do these changes happen?

Oct/Nov 2023

When large amounts of nitrates are carried into rivers, these changes may happen and fish may die. 1. Water plants die and sink to the river bed. 2. Bacteria increase very quickly. 3. The concentration of oxygen in the water falls. 4. More single-celled water plants grow, turning the water green. In what sequence do these changes happen?

Oct/Nov 2023

What human activity has done the most damage to tropical rainforests?

Oct/Nov 2024

A lake has been contaminated by sewage. How will the water in this lake differ from water that has not been polluted?

Oct/Nov 2024

Lake Victoria in Africa is one of the largest freshwater lakes on Earth. It is a key ecosystem for people who live around the lake and catch fish there as part of their diet.

Oct/Nov 2024