Evolution: Natural Selection & Adaptation

1. Evolution:Natural Selection & Adaptation Chapters 15 and 16

2. Evolution is the Unifying Principle of all Biology • forms foundation for all other concepts • answers all “why” questions • explains context of boil. phenomena • two major aspects: • descent from a common ancestor  why org. have similar characteristics • adaptation to environment  explains diversity of life • Charles Darwin • developed theory of evolution • 1859: The Origin of Species • descent with modification • “change through time” • evol. occurs through natural selection • env. determines which ind. will survive and reproduce • are fittestind.  possess best adaptations • adaptations • characteristics that increase chance of survival and reproduction

3. Natural Selection • mechanism of evol. • based on five key points: • ind. vary within pops. • some variation is inherited and affects survival • more offspring are produced than env. can support • offspring with most adaptive traits will survive better and produce more of their own offspring • offspring will also have the adaptive traits • over time, the pop. changes • more adaptive traits become more prevalent • environmental forces affect an individual’s phenotype • to survive, an org’s. phenotype must become adapted to env. • but, genotype determines phenotype • orgs. with most adaptive genotypes survive better and pass their genes onto their offspring • their genotypes produce a more fit and adaptive phenotype • such organisms are “selected for” • variation in pop.  small genetic changes  produce new genotypes  lead to new, better adapted phenotypes • continued phenotypic change  development of new species

4. variation • occurs in pops. in many different traits • behavioral, biochemical, physical • must be genetically based • two primary sources • mutation • source of new variations • crossing over • source of new combinations of traits • is very beneficial to a pop. evol. cannot occur without it • maintained through a wide variety of mechanisms • dispersal of young • masking recessive alleles • heterozygote advantage • others Fig. 15.7 Variation in a human population

5. Fig. 16.16 An example of heterozygote advantage

6. Modern Synthesis – Today’s Theory of Evolution • incorporates genetics into evolution • nat. sel. causes populations to change, not individuals • selection is not a random process • evol. is not based on the needs of organisms • mutations  acted on by nat. sel.  adaptation to local env. conditions • selection has been tested and confirmed many times in many organisms • fittest ind. are those more likely to survive, based on adaptations • evolution is not “survival of the fittest” • survival not as important as reproduction Fig. 16.3 Natural selection in peppered moths

7. Evidence and Examples of Evolution • fossil record • radioactive dating • hard-bodied vs. soft-bodied organisms • phylogenetic trees Fig. 17.17 Evolutionary history of Equus

8. Fig. 30.7 Human evolution

9. biogeography • study of where organisms are found on earth • provides evidence of past evol. history • isolated regions have their own types of plants and animals • similarity of unrelated species in similar environments Page 274 Biogeographical regions Fig. 15.5 An example of evidence through biogeography – the European hare and the Patagonian (S.A.) hare

10. Fig. 15.14 Biogeography. Some mammals of Australia and their North and South American counterparts.

11. comparative anatomy • homologous vs. analogous structures • adult and embryological evidence • transitional organisms • vestigial structures Fig. 15.16 Developmental homologies Fig. 15.15 Homologous structures

12. Fig. 15.13 Ambulocetus – an ancestor of whales and a transitional fossil Fig. 15.12 Transitional fossils - Archaeopteryx

13. Some vestigial structures Fig. 17.1 Whale evolution, showing transitional organisms

14. molecular biology • genetic code and cellular structure • DNA and amino acid similarities • number of mutations • phylogenetic trees Fig. 15.17 Biochemical differences – evidence from molecular biology

15. artificial selection • selective breeding Fig. 15.9 Artificial selection in plants Fig. 15.8 Artificial selection in animals