19.1.1Human Influences on Ecosystems
The Importance of Biodiversity — Cambridge IGCSE Co-ordinated Sciences 0654 - Biology Revision Notes & Topical Questions
5 min read 5 parts Lesson 2 of 3
Section 1 of 5Why habitats are destroyed
Habitat destruction
Growing population
- Growing population A larger human population needs more space for homes, food and resources, so rainforest, woodland and marine habitats are damaged.
Economic activities
- Economic activities Land is cleared to make way for farming, mining, building and industry.
Pollution
- Pollution Waste from human activities can poison habitats and make them unsuitable for the species that live there.
Broken food webs
- Broken food webs If one species disappears, the animals that fed on it may starve, so more species are lost.
Section 2 of 5Deforestation
1
Deforestation is the clearing of trees, usually on a large scale.
2
It can be sustainable only if the trees are replaced by replanting.
3
Usually the land is cleared for another use, such as building, cattle grazing or palm oil plantations, so it is not sustainable.
4
A plantation of one crop supports far fewer species than the original forest, so biodiversity falls.
5
As the area covered by trees shrinks, the harmful effects on the environment grow.
Section 3 of 5Effects of deforestation (Extended)
| Effect | Explanation (Extended tier) |
|---|---|
| Extinction of species | Habitats and food sources for animals and plants are removed, so some species have nowhere to live. |
| Loss of soil | Without roots to hold the soil, rain washes the topsoil away and nutrients are lost. |
| Flooding | Fewer trees take up and store water, so more rainwater runs quickly into rivers. |
| More carbon dioxide in the atmosphere | Fewer trees carry out photosynthesis, and burning or rotting trees releases carbon dioxide, which adds to global warming. |
Section 4 of 5Key terms
| Term | Meaning |
|---|---|
| Ecosystem | A community of organisms together with the non-living environment they interact with. |
| Biodiversity | The number of different species living in a particular area. |
| Habitat destruction | The damage or removal of the place where organisms live. |
| Deforestation | The clearing of trees, usually on a large scale. |
| Sustainable | Able to continue without using up resources or causing long-term damage. |
| Monoculture | A large area planted with a single type of crop. |
Section 5 of 5Exam technique
1
Defining biodiversity as the number of organisms. It is the number of different species.
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Saying that replanting never helps. Deforestation can be sustainable if trees are replaced.
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Listing only one effect of deforestation. Remember extinction, soil loss, flooding and carbon dioxide.
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Forgetting that losing one species can cause others to die because their food source has gone.
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