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Biodiversity Notes for Biology

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´╗┐Biodiversity, Evolution & Natural Selection Notes Biodiversity: * Variety of different organisms within a habitat. Two aspects to consider are: * Species richness: the number of different species within an area of known size at a particular time. A species is a group of organisms with so many features in common that they can mate and produce fertile offspring. * Genetic diversity: the genetic variation within a species Endemism: * Where a species is found in only one particular area * The ring tailed lemur is restricted to the island of Madagascar, so is endemic to Madagascar * Happens because the organism evolved within the region hasn?t migrated out to other areas Molecular phylogeny : * Compares the structure of a particular molecule from different organisms to discover their degree of evolutionary relatedness * The more similar the structure of the molecule, the more closely related the organisms are because changes in molecule structure generally occur slowly as they are caused by mutations * The ...read more.


survival and reproduction * Evolution is the change in the frequency of certain alleles in a gene pool over time due to natural selection Evolutionary sequence: * A population of organisms shows genetic diversity due to having a variety of alleles (caused by mutations) * Environmental conditions change * Natural selection removes some individuals with alleles that are not as advantageous * The remaining individuals grow and reproduce, passing on the advantageous alleles * Over many generations the frequency of these alleles increases Evaluation of new data: * All life is split into the prokaryotes and eukaryotes- most scientists agreed to this * A scientist called Woese suggested a third group which he called the archaea- published a paper in a scientific journal, could use internet or conference now * Other scientists study the evidence carefully, called peer review- scientists are checking that the evidence is accurate and correct, and that the conclusions drawn are sensible and that the methods used are appropriate * Other scientists ...read more.


* Any unusual genes in the founder members of the population may become amplified as the population grows-known as the founder effect Natural selection: * Survival of the fittest * If the niche changes due to changes in the environment, other characteristics may make an individual more successful * Natural selection will favour the survival of individuals with those different characteristics and we say the selection pressure has changed * Changes in selection pressure result in changes within the species Types of selection: * Directional selection: occurs anywhere that environmental pressure is applied to a population- frequently seen in insect populations that are seen as pests. Chemicals kill many instantly, but directional selection ensures that they become resistant over generations * Diversifying selection: occurs when conditions are very diverse and small subpopulations evolve different phenotypes suited to their very particular surroundings * Balancing selection: takes place when, as a result of natural selection, variety is maintained by keeping an allele with a population even though it might seem to be disadvantageous. ...read more.

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