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

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:

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

  

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