Human influences on the ecosystem

Question 1

Effects of deforestation-Species extinction through habitat loss

Answer 1

• Reduction of habitat or food sources leads to extinction

- Loss of forest habitat reduces plant and animal diversity - disrupts the food chain

Question 2

Effect of deforestation - loss of soil by soil erosion

Answer 2

Removal of trees means there are no roots to hold the soil, thin top layer of the soil is washed away during the rain

• Causes soil erosion and leaching of minerals
• Leads to desertification

Question 3

Effect of deforestation- flodding

Answer 3

Soil from erosion is washed into rivers, silting it and case flooding
- Forest id removed - no plant roots to take up rainwater - flows into streams and river - cause further flooding

Question 4

Effect of deforestation - CO2 build up

Answer 4

Forest have high rates of photosynthesis so it absorbs large amounts of CO2 - removal of forests contributes to increases carbon dioxide

Question 5

Describe the undesirable effects of overuse of fertilisers

Answer 5

• Fertilizers(soluble) are easily leached out into the soil and washed into rivers and lakes
• Algae absorb fertilizer and grow rapidly - form a blanket on the surface of water/blocking sunlight from algae below
• Algae and other plants die
• Bacteria decompose the dead algae and plants, using up oxygen in the water for respiration
• Animals in water die due to lack of oxygen

Question 6

Describe the undesirable effects of pollution to include: water pollution by sewage and chemical waste

Answer 6

Sewage(urine and faeces)
Sewage contains organic matter which bacteria break down, causing them to multiply and deoxygenate the water through aerobic respiration
- Sewage may contain disease-causing bacteria, which could get into drinking water supplies, causing cholera and typhoid

Question 7

Describe the undesirable effects of pollution to include: air pollution by greenhouse gases

Answer 7

CO2 is produced by burning of fossil fuels
- Methane is produced from the decay of organic matter and as a waste gas
Greenhouse gases trap heat in the earth’s atmosphere - concentration increase - more heat is trapped - atmosphere warmer
-Global warming

Question 8

Discuss the causes and effects on the environment of acid rain: sulphur dioxide and nitrogen oxides

Answer 8

Source: burning of fossil fuels and combustion of petrol in car engines
Effects:- damages leaves, killing plants
-Acidification of lakes, killing 
animals
-Corrosion of stonework
- Increase risk of asthma attack

Question 9

What are the solutions for the effects of acid rain?

Answer 9

• Changing the power stations from coal and oil to renewable energy sources
• Using catalytic converters in car exhausts to convert oxides of nitrogen to harmless nitrogen

Question 10

Describe the need for conservation of species and their habitats

Answer 10

• Many species are in danger of extinction due to habitat destruction and pollution
• The species may play an important role in a food chain
• Loss of rare species means that those genes is lost - important in future genetic engineering

Question 11

Describe the need for conservation of natural resources

Answer 11

• Increase the use of renewable energy

- Improve the efficiency of energy use(better insulation, smaller car engine, more public transport)

Question 12

Habitat can be conserved by:

Answer 12

• Using laws to protect the habitat

- Reducing public access to the habitat

Question 13

Oxides of nitrogen are found in the exhaust gases from cars. Suggest why these gases are formed in car engines.

Answer 13

Oxygen and nitrogen reacted together by high temperature