1 / 26

Adaptation and Evolution

Adaptation and Evolution. Evolution is the change in the inherited traits of a population of organisms through successive generations Two factors at work: Processes that constantly introduce variation in traits Processes that make particular variants become more common or rare. Evolution.

lulu
Download Presentation

Adaptation and Evolution

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript


  1. Adaptation and Evolution

  2. Evolution is the change in the inherited traits of a population of organisms through successive generations • Two factors at work: • Processes that constantly introduce variation in traits • Processes that make particular variants become more common or rare Evolution

  3. Variation is introduced to a population’s gene pool by: • Mutation: a heritable change in the nucleotide sequence of the genetic nucleic acid • Gene flow: introduction or loss of new alleles into the population through immigration or emigration • Genetic drift: stochastic shifts in allele frequencies in small populations • Natural selection: change in allele frequencies over generations due to differential survival and reproductive success of genotypes Evolution

  4. Point mutations are caused by random errors in the copying process (during transcription) TYPES OF MUTATIONS: Point mutation

  5. Chromosomal mutations occur when chromosomes fail to properly separate during meiosis TYPES OF MUTATIONS: Structural Modification Irregular Number

  6. Scientists disagree about how and why genes mutate • For a long time they believed that genetic mutations were unrelated to whatever consequences such mutations would have on the species. • Researchers have found evidence that cells might be able to "choose" which mutations will occur to give them an advantage in stressful situations. • For example, when starving, certain bacterial cells might generate multiple mutations. If the mutated cell survives, the mutation is passed on; cells that die take their unsuccessful mutations with them. • Flexibility in antibody production Why do genes mutate?

  7. Gene Flow Wilson & Bossert, 1971

  8. In each generation, some individuals may, just by chance, leave behind a few more descendents than other individuals The genes of the next generation will be the genes of the “lucky” individuals, not necessarily the healthier or “better” individuals It happens to ALL populations—there’s no avoiding the vagaries of chance Genetic Drift

  9. Genetic Drift

  10. Bottleneck

  11. Fitness is a measure of the ability of an individual to produce viable offspring and contribute to future generations • Individuals vary in their relative fitness due partly to genetic differences among individuals and partly to environmental influences • Individuals with greatest fitness will contribute disproportionately to subsequent generations Fitness

  12. As the environment changes so do the fitness values of the genotypes • Some properties of fitness: • Fitness is a property of a genotype, not of an individual or a population • Individuals with the same genotype share the same fitness within the same environment • Fitness is measured over one generation or more Fitness

  13. Natural selection may not produce a “perfectly-engineered” trait • Reasons why natural selection might not produce perfection • Lack of necessary genetic variation • Constraints due to history • Trade-offs Survival of “Fit Enough”

  14. Adaptation is the evolutionary process whereby a population becomes better suited to its habitat • Important for an organism's survival • Adaptations may be: • Physiological • Morphological • Behavioral • Adaptation is the result of natural selection Adaptation

  15. An adaptation is a feature that is common in a population because it provides some improved function Adaptations are well fitted to their function A vestigial structure is a feature that was an adaptation for the organism’s ancestor, but that evolved to be non-functional because the organism’s environment changed Adaptation

  16. What are selection pressures in an organism’s environment? • Biotic factors • Predation • Competition • Mutualism • Abiotic factors • Resource availability • Physical conditions • Chemical conditions Ecology and Evolution

  17. Natural selection leads to adaptive radiation and speciation

  18. “natural” or anthropogenic… Selection can be…

  19. Beak Adaptation

  20. No predators Exponential growth Environmental and crop damage 1859 Rabbits brought to Australia

  21. Introduced in 1950 Initially highly effective Reduced rabbits by 99% Now mortality rate is less than 50% Myxoma virus control

  22. Describe change in rabbit population

  23. Describe change in myoma virus

  24. Over many generations, mutations produce successive, small, random changes in traits, which are then filtered by natural selection and the beneficial changes retained Traits become suited to an organism's environment: these adjustments are called adaptations Ok: Survival of the fittest Better: those that can --- survive Natural Selection

  25. http://evolution.berkeley.edu/evosite/evo101/IIIDGeneticdrift.shtmlhttp://evolution.berkeley.edu/evosite/evo101/IIIDGeneticdrift.shtml Sources

More Related