20. Human influences on ecosystems
- Syllabus
- 0610–2026–2027
- Section
- 20
- Level
- —
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In this section
Topic 20.1
20.1 Food supply
Objectives in this topic
20.1.1—Humans have increased food production
- Describe how humans have increased food production, limited to: (a) agricultural machinery to use larger areas of land and improve efficiency (b) chemical fertilisers to improve yields (c) insecticides to improve quality and yield (d) herbicides to reduce competition with weeds (e) selective breeding to improve production by crop plants and livestock
20.1.2—Advantages and disadvantages
- Describe the advantages and disadvantages of large-scale monocultures of crop plants
20.1.3—Advantages and disadvantages
- Describe the advantages and disadvantages of intensive livestock production
Topic 20.2
20.2 Habitat destruction
Objectives in this topic
20.2.1—Biodiversity as the number
- Describe biodiversity as the number of different species that live in an area
20.2.2—Reasons for habitat destruction
- Describe the reasons for habitat destruction, including: (a) increased area for housing, crop plant production and livestock production (b) extraction of natural resources (c) freshwater and marine pollution
20.2.3—Through altering food webs and food
- State that through altering food webs and food chains, humans can have a negative impact on habitats
20.2.4—Undesirable effects of deforestation
- Explain the undesirable effects of deforestation as an example of habitat destruction, to include: reducing biodiversity, extinction, loss of soil, flooding and increase of carbon dioxide in the atmosphere
Topic 20.3
20.3 Pollution
Objectives in this topic
20.3.1—Effects of untreated sewage and excess
- Describe the effects of untreated sewage and excess fertiliser on aquatic ecosystems
20.3.2—Effects of non-biodegradable plastics
- Describe the effects of non-biodegradable plastics, in both aquatic and terrestrial ecosystems
20.3.3—Sources and effects of pollution
- Describe the sources and effects of pollution of the air by methane and carbon dioxide, limited to: the enhanced greenhouse effect and climate change
20.3.4—Process of eutrophication of water
- Explain the process of eutrophication of water, limited to: • 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
Topic 20.4
20.4 Conservation
Objectives in this topic
20.4.1—Sustainable resource as one which is
- Describe a sustainable resource as one which is produced as rapidly as it is removed from the environment so that it does not run out
20.4.2—Some resources can be conserved
- State that some resources can be conserved and managed sustainably, limited to forests and fish stocks
20.4.3—Organisms become endangered or extinct
- Explain why organisms become endangered or extinct, including: climate change, habitat destruction, hunting, overharvesting, pollution and introduced species
20.4.4—Endangered species can be conserved
- Describe how endangered species can be conserved, limited to: (a) monitoring and protecting species and habitats (b) education (c) captive breeding programmes (d) seed banks
20.4.5—Forests can be conserved using
- Explain how forests can be conserved using: education, protected areas, quotas and replanting
20.4.6—Fish stocks can be conserved using
- Explain how fish stocks can be conserved using: education, closed seasons, protected areas, controlled net types and mesh size, quotas and monitoring
20.4.7—Reasons for conservation programmes
- Describe the reasons for conservation programmes, limited to: (a) maintaining or increasing biodiversity (b) reducing extinction (c) protecting vulnerable ecosystems (d) maintaining ecosystem functions, limited to nutrient cycling and resource provision, including food, drugs, fuel and genes
20.4.8—Use of artificial insemination (AI)
- Describe the use of artificial insemination (AI) and in vitro fertilisation (IVF) in captive breeding programmes
20.4.9—Risks to a species if its population
- Explain the risks to a species if its population size decreases, reducing genetic variation (knowledge of genetic drift is not required)