Flashcards · 0610 · Topic 20

Human influences on ecosystems flashcards

19 cards on Topic 20, subtopics 20.1 to 20.4. Pick a subtopic or study them all.

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Ways agricultural machinery and chemical fertilisers increase food production: Machinery: larger areas can be farmed, more efficiently. Fertilisers: improved yields.
How insecticides and herbicides increase food production: Insecticides kill insect pests, improving quality and yield. Herbicides kill weeds, reducing competition with the crop.
Advantages and disadvantages of large-scale monocultures: For: efficient use of machinery, high yield, lower cost per unit. Against: low biodiversity, pests and diseases spread easily, heavy use of pesticides and fertiliser, habitats such as hedgerows removed.
Advantages and disadvantages of intensive livestock production: For: animals move less and are kept warm, so less energy is lost and they grow faster; high output at lower cost. Against: disease spreads quickly, waste can pollute water, welfare concerns, large amounts of crop feed needed.

Biodiversity: The number of different species that live in an area.
Reasons for habitat destruction: More land for housing, crop plants and livestock; extraction of natural resources; freshwater and marine pollution.
Undesirable effects of deforestation: Reduced biodiversity, extinction, loss of soil, flooding, and an increase in carbon dioxide in the atmosphere.
Why can deforestation cause flooding and loss of soil?: Fewer trees take up and transpire water, so more rain runs off; with no roots holding it, soil is washed away.

Effect of untreated sewage or excess fertiliser in a river: Sewage: bacteria decompose it, using up dissolved oxygen, so aquatic animals die. Fertiliser run-off: producers grow rapidly; when they die, decomposition lowers oxygen and animals die.
Effects of non-biodegradable plastics: Not broken down by decomposers. In water: animals become entangled or swallow plastic, and fragments enter food chains. On land: plastic fills landfill and traps or is eaten by animals.
Sources of carbon dioxide and methane: Carbon dioxide: combustion of fossil fuels, burning forests. Methane: livestock such as cattle, rice fields, landfill.
Enhanced greenhouse effect: Extra carbon dioxide and methane keep more thermal energy in the atmosphere, leading to climate change.
Eutrophication in six stepsExtended: More nitrate and other ions → more growth of producers → producers die and are decomposed → more aerobic respiration by decomposers → dissolved oxygen falls → organisms that need dissolved oxygen die.

Sustainable resource: One which is produced as rapidly as it is removed from the environment, so that it does not run out. Examples: forests and fish stocks.
Why species become endangered or extinct: Climate change, habitat destruction, hunting, overharvesting, pollution and introduced species.
How endangered species can be conserved: Monitoring and protecting species and habitats; education; captive breeding programmes; seed banks.
Methods for conserving fish stocksExtended: Education, closed seasons, protected areas, controlled net types and mesh size, quotas and monitoring.
Artificial insemination (AI) vs IVF in conservationExtended: AI: sperm collected from a male, stored or transported, and placed in a female. IVF: eggs fertilised outside the body; embryos placed in a female.
Why is a small population at greater risk of extinction?Extended: It has reduced genetic variation, so fewer individuals may have alleles that let them survive environmental change or a new disease.