Human Influences on the Environment

Question 1

What are the biological consequences of the pollution of water by toxic chemicals?

Answer 1

• Agricultural runoff can cause toxic chemicals to go into the water
• These chemicals, which cannot be easily broken down by organisms are absorbed by plants and invertebrates building up in their tissues overtime
• This is called bioaccumulation, and any predators who eat them will also ingest these compounds and levels of the chemicals will build up over time - eventually humans may eat the marine organisms and ingest the chemicals
• Eventually, the toxins will build up to dangerous levels within organisms, causing their death of failure to breed and disrupting food chains

Question 1

What are the biological consequences of eutrophication caused by leached minerals from fertilisers running into bodies of water?

Answer 1

• Excessive nutrients and minerals from fertilisers run in to the water
• Aquatic plants and algae flourish and bloom
• Algae blooms on the surface prevent light from reaching aquatic plants, causing the rate of photosynthesis to decrease and the oxygen levels to reduce
• The increase in dead plant matter causes an increase in aerobic respiration in decomposers, further causing levels of oxygen to fall
• As a resut of low oxygen levels, marine organisms will die

Question 2

What are the consequences of deforestation?

Answer 2

• Habitats are destroyed and biodiversity is decreased
• Soil is eroded due to the loss of stabilising roots, and all the nutrients that would otherwise have been used by trees are washed away by rain and leached into lakes and rivers causing eutrophication
• The loss of nutrients also makes it very hard for plant life to regrow in the area
• Less trees means less transpiration which causes lower levels of rainfall and drouts
• A lack of trees also means less stable soil which can be easily washed away, decreasing the protection against flooding
• Finally, the carbon cycle is disrupted as less carbon dioxide is being taken out of the atmosphere by trees, causing increased levels of atmospheric carbon dioxide
• This, coupled with the burning of trees after them being cut down which also increases levels of carbon dioxide, contributes to climate change