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ORIGIN OF SPECIES & MODERN THEORY OF EVOLUTION

ORIGIN OF SPECIES & MODERN THEORY OF EVOLUTION. Red Queen Hypothesis (Theory of Natural Selection). The environment is constantly changing Natural selection operates to enable the organisms to maintain their state of adaptation (not to improve it)

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ORIGIN OF SPECIES & MODERN THEORY OF EVOLUTION

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  1. ORIGIN OF SPECIES & MODERN THEORY OF EVOLUTION

  2. Red Queen Hypothesis (Theory of Natural Selection) • The environment is constantly changing • Natural selection operates to enable the organisms to maintain their state of adaptation (not to improve it) • For a species to remain in existence in a constantly changing environment, it must have enough of the right kind of heritable variation to change along with the environment • If genetic variation is inadequate, the species will go extinct

  3. Selection Pressure The degree to which the environment plays a role in survival • Low Selection Pressure • Low mortality • Lots of survival, more variability • New combinations can be tested • Includes any new genes and mutations

  4. High selection pressure • High mortality • Only the most fit survive • Eliminates all but the “best” genes • Population becomes specialized

  5. Environmental Change • Factors that determine our environment are constantly changing • Change occurs as a result of high selection pressure • Environment change may make all individuals less fit and extinction possible • Change occurs as a result of low selection pressure • More forms of gene present due to increased variability • Environment change may favour the different gene

  6. MODERN THEORY OF EVOLUTION

  7. Modern evolutionary synthesis • The modern theory of evolution that takes into account all branches of biology • Biologists today define evolution as changes in the gene pool of a species over time. • Gene pool: the complete set of alleles contained within a species or population

  8. Mutations: The Source of Variation • All species exhibit genetic variation • New or altered traits arise when new alleles and genes are produced by mutation and acted upon by natural selection

  9. http://evolution.berkeley.edu/evolibrary/article/1_0_0/eyes_10http://evolution.berkeley.edu/evolibrary/article/1_0_0/eyes_10

  10. Homologous Genes and Pseudogenes Homologous • All mammals have similar numbers and arrangements of bones because they have inherited this pattern from a common ancestor • Similarly closely related species inherit homologous genes, which mutate and evolve over time • The degree of similarity between homologous genes provides good evidence for the degree of relatedness between species • The more closely related two species are, the more similar we would expect their homolgous genes to be

  11. http://tables.pseudogene.org/collection.py?id=15

  12. Pseudogenes • pseudogene • A vestigial gene that no longer codes for a functioning protein; genes that have undergone mutations and no longer serve a useful purpose • Like vestigial anatomical features, a pseudogene is the remaining part of a gene that once serves a useful purpose • These genes are found virtually in all species

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