Biology Edexcel SNAB A Levels Biodiversity

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  • Biodiversity
    • Topic 4
      • Species richness: The number of different species living in the same area. Genetic Diversity: The genetic variation within species.
        • Species richness can be measured by random sampling. This is done by using 10 quadrats placed in random area, all the species found in each quadrat are recorded to estimate the total species richness
          • Genetic diversity can be measured by identifying the different alleles in a gene pool
      • Endemic:A species found in only one particular area
        • Molecular Phylogeny: The evolutionary relationship between species based on their molecular differences.
          • Three Domains: *Bacteria           *Archaea         *Eukaryota
      • Types of Adaptation: Anatomical = A physical adaptation which can be seen by the naked eye can be internal or external
        • Behavioural = Change in the organisms actions to increase survival chances
        • Physiological = Changes in the biochemical functioning of the organism in response to an altered environmental stimulus
      • Natural Selection: Survival of individuals in a population because they have advantageous alleles that improve their chances of survival and reproduction. Evolution: Change in the frequency of certain alleles in a gene pool over time due to natural selection.
      • Conservation: *Education       *Scientific Research          *Captive Breeding programmes    *Reintroduction programmes
    • Topic 5
      • Abiotic Factors: Non-living factos such as pollution and climate which affects the organisms survival in their habitat
        • Biotic factors: Living factors such as animals competing for food or mutualism which affects organisms survival in habitat.
      • Primary Succession: Newly formed habitat where there has not been a community established before
        • Secondary Succession: Newly formed habitat where an existing community has been cleared.
          • Deflected Succession: A community that remains stable only due to human activity prevents succession running its course.
      • Autotrophs:  Organisms that produce their own energy such as plants.
        • Primary consumers: Herbivores that eat plant materials Secondary Consumer: Carnivores that feed on primary consumers Tertiary Consumers: Carnivores at the top of the food chain
      • Speciation: Formation of new species due to environmental changes caused by selective pressure which lead to evolution by natural selection.
        • Ecological Isolation: When organisms become separate species due to living in different areas of their habitat.


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