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The Benefits of Biodiversity And Threats To It.

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________________ ________________ ________________ 2. Biodiversity is the variety of species on earth; extinction is the loss of species. Many new causes of extinction and lack of biodiversity have arisen which are directly attributable to human influences such as use of resources. ________________ ________________ ________________ ________________ 3. Reasons for species becoming endangered or extinct include: natural selection; habitat destruction such as deforestation and loss of hedgerows; pollution such as PCBs and oil; hunting and collecting; competition from domestic animals. ________________ ________________ ________________ Biodiversity is the variety of species on the earth. [Or if you prefer: Biodiversity is a contraction of ?biological diversity? and refers to the number, variety and variability of living organisms. It embraces two different concepts: one is a measure of how many different living things there are and the other is the measure of how different they are.] The benefits of biodiversity are: 1. ...read more.


Marine life has also been affected. About one third of the planet?s marine fish species rely on coral reefs. At the current rate of destruction, about half of the reefs could easily be lost in the next 20 years. About half the world?s forests have been cut down by deforestation during the last 30 years for reasons such as: the world demand for timber; wood can be used as a fuel; land is needed for farming; new roads; demand for paper and packaging. As well as the reduction in biodiversity caused by the loss of habitats, forests help to maintain a balance of carbon dioxide and oxygen in the atmosphere. Introduction of exotic species and competition from domestic animals Many exotic species are accidentally introduced, such as certain weeds and insect pests. Others are deliberate. For example, foxes, rabbits and cats were taken to Australia aboard European ships and have since ruined Australia?s indigenous wildlife. ...read more.


Their use has been banned or severely restricted in many countries since the 1970s and 80s because of the possible risks to human health and the environment. An oil spill is the release of a liquid petroleum hydrocarbon into the environment due to human activity, and is a form of pollution. Oil spills affect marine life by physical contamination or by smothering or by the bioaccumulation of the toxic components of oil in animal and plant tissues. Natural Selection The organisms that are better adapted to their environment are more likely to survive and reproduce offspring that are successful. There is a struggle for survival (competition between animals of the same species), with only those with the best genetic advantages surviving. These individuals reproduce and pass on their successful characteristics to their offspring, giving the next generation a selective advantage. When the environment or conditions change, the features needed to survive in it changes, so natural selection is continuous process. Natural selection can also maintain variation if there is no need to change and therefore stabilises a population. ...read more.

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