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  • Biodiversity
    • Biodiversity is 'A measure of the number of species in a given area'
    • A species is 'A group of organisms that share a large number of common characteristics and can be interbred and produce fertile offspring'
    • Species diversity is 'The number of different species and the proportion of each species within a given area'
    • There are 25 hotspots of biodiversity around the world
      • Tropical rain forests and coral reefs are the most diverse habitats in the world
    • The number of species per square km increases as one moves from the poles to the tropics
      • Biodiversity is important because species are linked within ecosystems
        • If one species increases or decreases in number, it will affect other species within the ecosystem
    • The fossil record shows that the majority of all known organisms are now extinct
      • Extinction: 'Loss of a species'
        • Extinction is a natural process that has been occuring since life began. It is the current rate of extinction that is creating the biodiversity process
    • Major reasons for decline in biodiversity;
      • Loss of habitat due to deforestation
      • Loss of habitat due to pollution
      • Competition from the introduction of an 'alien' species
      • Loss of habitat due to drainage of wetlands
      • Over hunting by humans
    • Evolution
      • Evolution is the process by which new species are formed from pre-existing ones over a period of time
        • Evolution gives rise to variation
        • It involves a change in an organisms genotype and phenotype
      • Evolutionary history shows there have been 5 mass extinction events, when most species became extinct - these are referred to as bottlenecks in biodiversity
        • Since the mass extinctions, the fossil record shows that biodiversity has increased and new species have radiated out from a common ancestor
          • Natural selection brings about the evolution of species from a common ancestor. This is known as adaptive radiation
      • Adaptive radiation is 'The emergence of a new species from a common ancestor introduced to an environment'
        • Adaptive radiation occurs;
          • Following mass extinctions
          • When a species moves to a new area with lots of ecological opportunities
      • Natural Selection
        • Darwin's observations of variation within a population lead to the development of natural selection and the belief that natural selection drives evolution of new species
          • The basic principle of natural selection is that organisms better suited to their environment will survive and reproduce to produce successful offspring
      • Darwin's Finches
        • In 1832, Charles Darwin travelled to South America to carry out a scientific survey
          • He studies the flora and fauna of mainland South America and some of the surrounding islands, including the Galapagos islands
            • Among the many animals that Darwin studies on the Galapagos islands were the finches, of which he observed 14 different species
              • The islands were recently formed and therefore any animals or plants found there must have reached the islands from the mainland, 600 miles away
                • Finches cannot fly long distances so Darwin suggested that one common ancestor of the finches had reached the islands with the help of high winds/driftwood
                  • Darwin noticed that individual finches differed from one island to the next. The main differences were the shape and size of their beaks and that these were related to the different foods that were available on each island
                    • It seemed that on each island, the characteristics that best suited a finch to it's environment were inherited by the offspring. Darwin suggested that the different finches had developed from one common ancestor and that the type or beak had developed over time and become specialised to feed on a particular food source
                      • This is an example of adaptive radiation


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