20. Human influences on ecosystems

21.1 Food supply

Core

• State how modern technology has resulted in increased food production in terms of:

– agricultural machinery to use larger areas of land and improve efficiency

– chemical fertilisers to improve yields

– insecticides to improve quality and yield

– herbicides to reduce competition with weeds

– selective breeding to improve production by crop plants and livestock, e.g. cattle, fish and poultry

• Describe the negative impacts to an ecosystem of large-scale monocultures of crop plants

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

21.2 Habitat destruction

Core

• Describe the reasons for habitat destruction, limited to:

– increased area for food crop growth, livestock production and housing

– extraction of natural resources

– marine pollution

• State that through altering food webs and food chains, humans can have a negative impact on habitats

• List the undesirable effects of deforestation as an example of habitat destruction, to include extinction, loss of soil, flooding and increase of carbon dioxide in the atmosphere

Supplement

• Explain the undesirable effects of deforestation on the environment

21.3 Pollution

Core

• State the sources and effects of pollution of land and water, e.g. rivers, lakes and the sea, by insecticides, herbicides and by nuclear fall-out

• State the sources and effects of pollution of water (rivers, lakes and the sea) by chemical waste, discarded rubbish, untreated sewage and fertilisers

• State the sources and effects of pollution of the air by methane and carbon dioxide, limited to the enhanced greenhouse effect and climate change

Supplement

• Explain the process of eutrophication of water in terms of:

– increased availability of nitrate and other ions

– increased growth of producers

– increased decomposition after death of producers

– increased aerobic respiration by decomposers

– reduction in dissolved oxygen

– death of organisms requiring dissolved oxygen in water

• Discuss the effects of non-biodegradable plastics in the environment, in both aquatic and terrestrial ecosystems

• Discuss the causes and effects on the environment of acid rain

• State the measures that are taken to reduce sulfur dioxide pollution and reduce the impact of acid rain

• Explain how increases in carbon dioxide and methane concentrations in the atmosphere cause an enhanced greenhouse effect that leads to climate change

• Describe the negative impacts of female contraceptive hormones in water courses, limited to reduced sperm count in men and feminisation of aquatic organisms

21.4 Conservation

Core

• Define a sustainable resource as one which is produced as rapidly as it is removed from the environment so that it does not run out

• Explain the need to conserve non-renewable resources, limited to fossil fuels

• State that some resources can be maintained, limited to forests and fish stocks

• State that products can be reused or recycled, limited to paper, glass, plastic and metal

• Outline how sewage is treated to make the water that it contains safe to return to the environment or for human use

• Explain why organisms become endangered or extinct, limited to climate change, habitat destruction, hunting, pollution and introduced species

• Describe how endangered species can be conserved, limited to monitoring and protecting species and habitats, education, captive breeding programmes and seed banks

Supplement

• Define the term sustainable development as development providing for the needs of an increasing human population without harming the environment

• Explain how forests and fish stocks can be sustained using education, legal quotas and restocking

• Explain that sustainable development requires: – management of conflicting demands – planning and cooperation at local, national and international levels

• Explain the risks to a species if the population size drops, reducing variation (knowledge of genetic drift is not required)

• Explain reasons for conservation programmes, to include:

– reducing extinction

– protecting vulnerable environments

– maintaining ecosystem functions, limited to nutrient cycling and resource provision, e.g. food, drugs, fuel and genes