CIE IGCSE Biology: 复习笔记:20.1.2 The Importance of Biodiversity

CIE IGCSE Biology: 复习笔记:20.1.2 The Importance of Biodiversity

Human Pressures on Other Species

Biodiversity

  • Is defined as the number of different species that live in a particular area
  • Human activities have tended to force biodiversity downwards, whereas, high bidiversity is needed for stable ecosystems
  • Habitat destruction by humans is a major downward pressure on biodiversity

Reasons for Habitat Destruction

 

  • The increasing human population of the planet is causing destruction of many habitats from rainforest to woodland to marine
  • Many habitats are destroyed by humans to make space for other economic activities, or by pollution from these activities, and this reduces the biodiversity of these areas
  • This interrupts food chains and webs, meaning that more species may die because their prey is gone
  • The main reasons for habitat destruction include:

 

21.2-Habitat-Destruction-table

 

Deforestation

 

  • Deforestation is the clearing of trees (usually on a large scale)
  • If trees are replaced by replanting it can be a sustainable practise
  • Generally the trees are being cleared for the land to be used in a different way (for building, grazing for cattle, planting of monocultures such as palm oil plantations etc) and therefore it is not sustainable
  • As the amount of the Earth’s surface covered by trees decreases, it causes increasingly negative effects on the environment and is a particularly severe example of habitat destruction
  • Undesirable effects of deforestation include:
    • Extinction of species
    • Loss of soil
    • Flooding
    • Increase of carbon dioxide in the atmosphere

     

 

 

21.2-Consequences-of-Deforestation-table

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