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Evolution: Natural Selection & Adaptation. Chapters 15 and 16. 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: - PowerPoint PPT Presentation
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Evolution:Natural Selection & Adaptation
Chapters 15 and 16
I. Evolution is the Unifying Principle of all BiologyA. forms foundation for all other concepts
1. answers all “why” questions2. explains context of boil. phenomena
B. two major aspects:1. descent from a common ancestor why org. have similar characteristics2. adaptation to environment explains diversity of life
II. Charles DarwinA. developed theory of evolution
• 1859: The Origin of SpeciesB. descent with modification
• “change through time”C. evol. occurs through natural selection
1. env. determines which ind. will survive and reproduce• are fittest ind. possess best adaptations
2. adaptations• characteristics that increase chance of survival and reproduction
III. Natural SelectionA. mechanism of evol.B. based on five key points:
1. ind. vary within pops.2. some variation is inherited and affects survival3. more offspring are produced than env. can support4. offspring with most adaptive traits will survive
better and produce more of their own offspring• offspring will also have the adaptive traits
5. over time, the pop. changes• more adaptive traits become more prevalent
C. environmental forces affect an individual’s phenotype1. to survive, an org’s. phenotype must become adapted to env.
• but, genotype determines phenotype2. orgs. with most adaptive genotypes survive better and pass their genes
onto their offspring• their genotypes produce a more fit and adaptive phenotype
o such organisms are “selected for”3. variation in pop. small genetic changes produce new genotypes lead
to new, better adapted phenotypes4. continued phenotypic change development of new species
D. variation1. occurs in pops. in many different traits
a. behavioral, biochemical, physicalb. must be genetically basedc. two primary sources
i. mutation• source of new variations
ii. crossing over• source of new combinations of traits
d. is very beneficial to a pop. evol. cannot occur without it2. maintained through a wide variety of mechanisms
a. dispersal of youngb. masking recessive allelesc. heterozygote advantaged. others
Fig. 15.7 Variation in a human population
Fig. 16.16 An example of heterozygote advantage
E. Modern Synthesis – Today’s Theory of Evolution• incorporates genetics into evolution
F. nat. sel. causes populations to change, not individualsG. selection is not a random processH. evol. is not based on the needs of organisms
• mutations acted on by nat. sel. adaptation to local env. conditionsI. selection has been tested and confirmed many times in many organismsJ. fittest ind. are those more likely to survive, based on adaptations
1. evolution is not “survival of the fittest”2. survival not as important as reproduction
Fig. 16.3 Natural selection in peppered moths
IV. Evidence and Examples of EvolutionA. fossil record
1. radioactive dating2. hard-bodied vs. soft-bodied organisms3. phylogenetic trees
Fig. 17.17 Evolutionary history of Equus
Fig. 30.7 Human evolution
B. biogeography1. study of where organisms are found on earth2. provides evidence of past evol. history3. isolated regions have their own types of plants and animals4. 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
Fig. 15.14 Biogeography. Some mammals of Australia and their North and South American counterparts.
C. comparative anatomy1. homologous vs. analogous structures2. adult and embryological evidence3. transitional organisms4. vestigial structures
Fig. 15.15 Homologous structures
Fig. 15.16 Developmental homologies
Fig. 15.12 Transitional fossils - Archaeopteryx
Fig. 15.13 Ambulocetus – an ancestor of whales and a transitional fossil
Fig. 17.1 Whale evolution, showing transitional organisms
Some vestigial structures
D. molecular biology 1. genetic code and cellular structure2. DNA and amino acid similarities3. number of mutations4. phylogenetic trees
Fig. 15.17 Biochemical differences – evidence from molecular biology
E. artificial selection• selective breeding
Fig. 15.8 Artificial selection in animals
Fig. 15.9 Artificial selection in plants