Summary
Human influences on ecosystems involve various activities that impact biodiversity, soil fertility, and atmospheric conditions. These influences can lead to issues such as eutrophication, deforestation, and global warming.
- Eutrophication — the process where water bodies become enriched with nutrients, leading to excessive algae growth. Example: Fertilisers entering from farmland cause algae blooms in lakes.
- Deforestation — the removal of trees, which reduces biodiversity and soil fertility. Example: Cutting down forests for agriculture decreases habitat for species.
- Biomagnification — the increase in concentration of substances, like pesticides, in organisms at higher trophic levels. Example: Large fish accumulate more pesticides than smaller organisms.
- Greenhouse gases — gases like carbon dioxide and methane that trap heat in the atmosphere. Example: Burning fossil fuels releases CO₂, contributing to global warming.
Exam Tips
Key Definitions to Remember
- Eutrophication: Nutrient enrichment in water bodies causing algae blooms.
- Deforestation: Clearing of forests, reducing biodiversity and soil fertility.
- Biomagnification: Increase in concentration of substances in organisms at higher trophic levels.
- Greenhouse gases: Gases that trap heat in the atmosphere, like CO₂ and methane.
Common Confusions
- Fertiliser runoff vs. sewage: Both cause eutrophication but originate from different sources.
- Herbicides vs. insecticides: Herbicides target plants, while insecticides target insects.
Typical Exam Questions
- What causes eutrophication? Fertilisers and sewage entering water bodies.
- How does deforestation affect ecosystems? It reduces biodiversity and soil fertility.
- What is biomagnification? The increase in concentration of substances in organisms at higher trophic levels.
What Examiners Usually Test
- Understanding of how human activities impact ecosystems.
- Ability to explain processes like eutrophication and biomagnification.
- Knowledge of the effects of greenhouse gases on global warming.