Effects of Humans on Ecosystems (Cambridge O Level Biology)

Deforestation can cause an increase in the concentration of carbon dioxide in the atmosphere.

State two other undesirable effects of deforestation.

[2]

State two uses for land that has been cleared of trees.

Table 1 shows the area of forest that was removed in Brazil each year between 2006–2010.

Table 1

Give your answer in km². Show your working.

[2]

Describe the trend in the data shown in Table 1.

Suggest two reasons for the trend you have described in part (ii).

Some animals are farmed intensively.

Describe the negative impacts to an ecosystem of intensive livestock production.

State why fertilisers, herbicides and insecticides are used in farming.

Fertilisers, herbicides and insecticides can all pollute water.

List two other sources of water pollution.

Fig. 1 shows a photograph of an area where the trees have been cut down.

Fig. 1

State the name of the type of habitat destruction shown in Fig. 1.

[1]

State three human activities, other than cutting down large areas of trees, that can cause habitat destruction.

Human activity can cause pollution of the environment.

Table 1 shows some pollutants, the environment they pollute and some of the effects.

Complete Table 1.

Table 1

A farmer has not used any insecticides or artificial fertilisers on a crop. 

Explain ways in which this may help the local environment.

Many scientists predict that, as the world’s human population increases, there will be a shortage of food.

Suggest and explain why an increase in human population is predicted to lead to a global human food shortage.

Fig.1 shows a river and the location of a fertiliser factory. The arrows indicate the direction of the flow of the river.

Fig. 1

A scientist recorded the nitrate concentrations of the water at site A and site B. 

Table 1 shows the results of this investigation.

Table 1

Calculate the percentage difference in the mean nitrate concentration between site A and B.

Show your working and state the nature of the difference.

Scientists observed algae and dead fish at site B.

Suggest an explanation for these observations.

Explain the importance of using chemical fertiliser in modern farming practices.

The graph in Fig. 1 shows the area of forest land lost in Ecuador in the years 2014 - 2019 inclusive. 

Fig. 1

Calculate the total area of land lost to deforestation in Ecuador from the beginning of 2014 to the end of 2019. 

Identify in Table 1 below the possible reasons for the change in the area of forest lost per year between 2014 and 2017.

Place a tick (✓) in the boxes below that apply.

Table 1

Suggest two explanations for the reductions in loss of forest land in Ecuador in the years 2018 and 2019.

Conservationists looking at the data in Fig. 1 would not be fully satisfied with the 2018 - 2019 trend shown in the data.

Explain why.