Diversity & Evolution

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  1. Charles Darwin's theory of natural selection
    • Overproduction of offspring - reproductive potential exceeds replacement
    • Constancy of population size - food supply limited
    • Struggle for existence - individuals constantly compete with one another for food etc only a few survive and reproduce
    • Variation within a population - inidividuals differ, variations are inherited, environment selects for certain ones and against others
  2. Natural Selection
    • Individuals who possess favourable characteristics survive better in existing environmental conditions
    • Organisms that are selected for reproduce and leave more offspring - Greater reproductive success and beneficial traits are passed to their offspring
    • Less favourable individuals eliminated over time
  3. Descent with Modification
    Over generations, proportion of individuals possessing advantageous characteristic increase in population
  4. Source of variation found in a population
    Mutation (gene/chromosomal) - only source that produces new alleles

    • Crossing over
    • Independent Assortment in meiosis
    • Random fusion of gametes
    • (These produces new allele combinations)
    • Allele frequency in gene pool change
  5. Natural Selection
    Process in which organisms with certain inherited characteristics are more likely to survive and reproduce than organisms with other characteristics
  6. NS due to environmental factors
    exerting a selection pressure on the individuals
  7. Genetic variation results in
    • phenotypic variation
    • Organisms with traits which enable them to better adapt to environment will be selected for
  8. Selected for organisms
    are likely to survive, reproduce and pass their genes coding for such advantageous traits to the offspring
  9. Differential Reproductive Success
    • Allele frequencies of these advantageous traits will increase in the population
    • This increases freq of individuals with favourable adaptations in the population
  10. Selection
    process whereby due to selection pressure, one phenotype leaves more offspring than another phenotype
  11. Fitness - reproductive success
    More surviving offspring an individual has, greater the number of copies of that inidividual's gene is present in future generations and the greater the individual's reproductive fitness
  12. Variation is what natural selection acts on
    Phentypes best suited for environmental conditions will be selected for, leading to differential reproductive success of certain phenotypes
  13. Genetic variations (recessive alleles per se) are protected from being eliminated through NS
    • Diploidy
    • Heterozygote advantage
    • Frequency Dependent Selection
    • Neutral Variation
  14. Diploidy
    • Recessive alleles not expressed in heterozygotes in diploid organisms hence will not come under selection pressure
    • Hence recessive allele still can be passed down through heterozygote, preserving it in the popln
  15. Heterozygote superiority
    • Heterozygote greater ability to survive and greater reproductive success than homozygote
    • i.e sickle celled allele increase resistance to malaria, convers advantage
    • allele harmful in homozygote - heterozygote advantage cause it to be preserved
  16. Frequency dependent selection
    • Fitness of a phenotype dependent on frequency relative to other phenotypes
    • i.e if alot, common, predator will eat most of them, if rare have advantage of survival suffers less predation than common ones
  17. Neutral Variation
    • Non coding DNA in eukaryotes
    • Variation in non coding DNA are neutral hence do not affect phenotype
    • Mutations occur in coding regions maybe neutral due to degenerate genetic code - more than 1 genetic code coding for 1 A.A
    • Will not come under neutral variations
  18. Evolution
    change in heritable traits of population over successive generations
  19. Microevolution
    change in allele frequency in gene pool of population over time
Card Set
Diversity & Evolution
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