13 Human Influences on Ecosystems

Question 1

Describe the Carbon cycle

Answer 1

A cycle that recycles the finite resource of carbon to allow new organisms to be made and grow. Carbon dioxide is taken from atmosphere with photosynthesis. Passed on to animals and carbon dioxide is returned as a result of respiration. If animals die and decomposing microorganisms are not present, they become fossil fuels over millions of years. When they are burned, they release carbon dioxide into the atmosphere.

Question 2

Effect of increased use of fossil fuels and mass deforestation on carbon dioxide and oxygen concentrations in the atmosphere

Answer 2

Increased use of fossil fuels increases the CO2 content and reduces oxygen content as the carbon combines with oxygen to make CO2, and mass deforestation reduces the amount of producers available to take carbon dioxide out of atmosphere and release oxygen.

Question 3

Effects of Deforestation

Answer 3

Habitat destruction, extinction, loss of soil, flooding, and increase of CO2 in the atmosphere. Plants are also a major carbon store so if they are cleared, burned or left to rot, the carbon is released into the atmosphere.

Question 4

Sources and effects of pollution of water: Chemical waste

Answer 4

Source: Industries produce liquid waste that is disposed into water systems.
Effect: Sewage leads to eutrophication, but other toxic substances have to be removed completely because they do not break down and are absorbed by plants and animals, damaging food chains and webs.

Question 5

Sources and effects of pollution of water: Discarded rubbish

Answer 5

Source: Much rubbish consists of plastic that is either discarded or buried in landfills.
Effect: Plastics are non-biodegradable and remain in the environment for hundreds of years. Animals also eat them and can get into food chains this way.

Question 6

Sources and effects of pollution of water: Untreated sewage

Answer 6

Source: lack of sewage treatment plants in inhabited areas due to poor infrastructure and lack of money.
Effect: Provides a good source of food for bacteria which increase rapidly, depleting the oxygen dissolved in the water as they respire aerobically and causing the death of aquatic organisms. This is known as eutrophication.

Question 7

Sources and effects of pollution of water: Fertilisers

Answer 7

Source: Runoff from agricultural land if applied in too high concentration.
Effect: Causes Algal blooms which then die and provide a good source of food from decomposing bacteria which increase rapidly, depleting the oxygen dissolved in the water and causing death of aquatic organisms such as fish. This is known as eutrophication.

Question 8

Problems with the decay of non-biodegradable plastics

Answer 8

May break down into small particles called nurdles which are swallowed by animals by mistake
May be broken down to release toxins
Plastic bags may be swallowed by animals
Plastic nets or ropes may entangle animals and cause suffocation.

Question 9

Define and explain eutrophication

Answer 9

A natural process that occurs when a body of water becomes enriched with nutrients. Excessive nutrient can lead to an overabundance of plant growth. As they grow faster, they respire more rapidly taking oxygen from the water, leaving less oxygen in the water for other organisms, causing them to die.
This could however be caused by the runoff of fertilisers from farmland entering the water to cause the increased growth of algae and water plants.