B4: Living organisms in their environment

• Humans and the environment

• Ecosystems

Humans and the environment

Candidates will be assessed on their ability to:

• understand the principles of interdependence, adaptation, competition and predation; explain how these factors influence the distribution and population sizes of organisms in a given terrestrial or aquatic environment (B4.01)

• describe the impact of human activity on the environment, including the pollution of air and of water; recall the effects of air pollutants (eg sulfur dioxide, carbon monoxide) and of water pollutants (eg sewage, nitrates and phosphates) (B4.02)

• relate the level of impact on the environment to population size, economic factors and industrial requirements (B4.03)

• describe the effects of deforestation and overfishing; understand the importance of protecting natural populations (B4.04)

Ecosystems

Candidates will be assessed on their ability to:

• describe food chains quantitatively using pyramids of biomass (B4.05)

• understand that energy is transferred through food chains and that energy and biomass are lost between trophic levels (B4.06)

• understand that energy transfer can be maximised in food production, for example in fish farms (B4.07)

• explain the techniques used to maximise food production in terms of optimum feeding conditions, disease and predator control (B4.08)

• describe the stages in the carbon cycle, including the roles of micro-organisms; interpret carbon cycle diagrams (B4.09)

• describe the stages in the nitrogen cycle, including the roles of nitrogen-fixing bacteria, decomposers, nitrifying bacteria and denitrifying bacteria (specific names of bacteria are not required); interpret nitrogen cycle diagrams (B4.10)

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