Human influence on ecosystem

The table shows some information about two closely related species of sea bird.

Sewage pollution at the mouth of a river destroys its fish stocks. What is likely to happen to local populations of these birds?

• A There will be no change to either species.

• B Species X numbers will decrease, species Y will remain constant.

• C Species Y numbers will decrease, species X will remain constant.

• D Both species numbers will increase

A large amount of herbicide is applied to a field. Heavy rainfall carries much of it into a nearby lake.

What will be the effect of this on the lake?

• A Herbicide decreases the growth of water plants.

• B Herbicide decreases the number of bacteria.

• C Herbicide increases the rate of evaporation from the lake.

• D Herbicide kills the fish.

The diagram shows four positions on a river where water samples were taken.

Which graph shows oxygen concentrations in the river?

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Which process may result in eutrophication in a lake?

• A bleach entering from a factory

• B fertilisers entering from farmland

• C hot water entering from a power station

• D pesticides entering from farmland

Over-use of fertilisers on farmland causes the chemicals in the fertilisers to be washed into ponds and lakes.

This causes eutrophication resulting in the following events.

1 algae grow

2 fish die

3 bacteria grow

4 oxygen decreases

What is the correct sequence of these events?

• A 1 → 3 → 4 → 2

• B 1 → 4 → 3 → 2

• C 3 → 4 → 2 → 1

• D 4 → 1 → 2 → 3

The graph shows changes in part of a lake after it has been polluted by fertilisers from a nearby farm.

At which time will the oxygen concentration in the water be lowest?

• A

• B

• C

• D

Which feature of deforestation has the greatest effect on the atmosphere?

• A extinction of forest animal species

• B increased risk of flooding

• C reduction of photosynthesis

• D soil erosion

On the map shown, sulfur dioxide is produced at X. Which region is most likely to experience acid rain?

• A

• B

• C

• D

Different pesticides were tested to see how poisonous they were to fish. Scientists found the concentration of pesticide that killed 50% of the fish within four days.

The table shows the results of the tests.

Which pesticide was the most dangerous to the fish?

• A DDT

• B dieldrin

• C malathion

• D parathion

A persistent pesticide is one that does not break down. What is one disadvantage of a persistent pesticide?

• A It becomes more concentrated at each level in the food chain.

• B It breaks down within a few months

• C It only destroys one particular pest in the food chain.

• D It does not dissolve in water.