Revision notes · Ecology
Biodiversity and the effect of human interaction on ecosystems
Biodiversity4.7.3.1
Definition: Biodiversity is the variety of all the different species of organisms on Earth, or within an ecosystem.
High biodiversity ensures the stability of ecosystems by reducing the dependence of one species on another.
- •A high biodiversity ensures the stability of an ecosystem by reducing the dependence of one species on another for food, shelter, and maintaining the physical environment.
- •The expanding human population and increasing standard of living mean that humans are using more natural resources.
- •Human activities produce large amounts of waste, which causes pollution unless properly managed.
- •Unless human activities and waste generation are controlled, biodiversity will continue to decrease.
⚠️ Common mistake: Confusing biodiversity with the total number of individual organisms, rather than the variety of different species.
🧠 Remember: High biodiversity = a stable, resilient ecosystem.
Waste management4.7.3.2
Definition: Waste management involves treating and disposing of human waste safely to prevent pollution and protect ecosystems.
Rapid population growth leads to increased waste production, causing severe air, water, and land pollution.
| Type | Caused by |
|---|---|
| Water | Untreated sewage, agricultural runoff containing fertilisers, toxic industrial chemicals |
| Air | Smoke and acidic gases (e.g. sulfur dioxide), which lead to acid rain |
| Land | Toxic chemicals (pesticides, herbicides), waste disposed of in landfill |
- •Pollution kills plants and animals, which reduces biodiversity in affected ecosystems.
⚠️ Common mistake: Thinking fertilisers directly poison aquatic life, rather than causing an algal bloom that leads to oxygen depletion by decomposers.
🧠 Remember: Pollution harms three main areas: water, air, and land.
Land use4.7.3.3
Definition: Land use refers to the clearing and modification of natural land by humans for agriculture, housing, quarrying, and waste disposal.
Human land use reduces the overall area of natural habitat available for other species.
- •Humans reduce the amount of land available for plants and animals by building, farming, quarrying, and dumping waste.
- •The destruction of peat bogs to produce cheap garden compost reduces the area of this habitat and its biodiversity.
- •Decaying or burning peat releases stored carbon into the atmosphere as carbon dioxide, contributing to global warming.
- •There is a conflict between cheap compost production for food and the conservation of peat bogs.
⚠️ Common mistake: Forgetting that decaying peat releases carbon dioxide through microbial respiration, not just when it is burned.
🧠 Remember: Destroying peat bogs releases carbon dioxide and destroys unique habitats.
Deforestation4.7.3.4
Definition: Deforestation is the large-scale removal of trees and forests from land that is then converted to non-forest use.
Large-scale deforestation in tropical regions cleared land for agriculture, causing serious environmental damage.
- •Deforestation primarily occurs to clear land for cattle, rice fields, and growing crops for biofuels.
- •Loss of trees reduces the amount of carbon dioxide removed from the atmosphere via photosynthesis.
- •Burning cleared wood and microbial decay of dead trees release carbon dioxide back into the atmosphere.
- •Deforestation causes a severe loss of habitats, leading to extinctions and a reduction in biodiversity.
⚠️ Common mistake: Believing that living trees release carbon dioxide when cut down, rather than releasing it when burned or decayed.
🧠 Remember: Deforestation = less photosynthesis, more carbon dioxide, lower biodiversity.
Global warming4.7.3.5
Definition: Global warming is the gradual increase in the Earth's average surface temperature caused by rising levels of greenhouse gases.
Increasing atmospheric levels of carbon dioxide and methane trap heat, driving global climate change.
- •Carbon dioxide and methane are key greenhouse gases that absorb infrared radiation and warm the atmosphere.
- •Biological consequences include loss of habitats due to rising sea levels from melting ice caps.
- •Changing global weather patterns affect temperature and rainfall, altering where species can survive.
- •Changes in migration patterns and species distributions can lead to extinction and reduced biodiversity.
⚠️ Common mistake: Confusing global warming with the hole in the ozone layer.
🧠 Remember: Greenhouse gases trap heat, causing climate change and habitat loss.
Maintaining biodiversity4.7.3.6
Definition: Maintaining biodiversity involves direct human interventions and conservation strategies designed to protect habitats and species.
Programs have been put in place by scientists and governments to reduce human impact on ecosystems.
- •Breeding programmes for endangered species help prevent extinction and boost population numbers.
- •Protection and regeneration of rare habitats, such as coral reefs, mangroves, and peat bogs, preserve ecosystem stability.
- •Reintroduction of field margins and hedgerows in farmland provides habitats and food sources for wild organisms.
- •Government targets to reduce deforestation and carbon emissions, alongside increased recycling, help preserve habitats.
⚠️ Common mistake: Assuming that recycling alone is sufficient to maintain biodiversity without active habitat protection.
🧠 Remember: Breed, protect, replant, and recycle to preserve ecosystems.
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