Adaptation and Evolution

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

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

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

7. 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?

8. Gene Flow Wilson & Bossert, 1971

9. 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

10. Genetic Drift

11. Bottleneck

12. 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

13. 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

14. 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”

15. 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

16. 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

17. 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

18. Natural selection leads to adaptive radiation and speciation

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

20. Beak Adaptation

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

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

23. Describe change in rabbit population

24. Describe change in myoma virus

25. 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

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