Next Unit is Ch 22-26 Ch 22. Charles Darwin

1. Next Unit is Ch 22-26Ch 22. Charles Darwin

2. H.M.S Beagle (1831-36) • Noticed that plants and animals from different parts of the world had distinct different characteristics • Those in same climate on different continent looked same • Compared animals in Galapagos with those in South America (finches and lizards) • Similar, but different and unique

3. Origin of Species (1859) • Finally published abstract • Only published because of Alfred Wallace • Young scientist who came up with same theory • He was supposed to publish larger multi-volume dissertation • Descent with Modification (evolution) • Descent from unknown common ancestor • Over millions of years, they accumulate diversity • see fig. 22.7

4. Theory of Natural Selection ************** • Five observations • All species have such great potential fertility • Populations remain stable in numbers • Environmental resources are limited • Individuals vary within population • Much variation is heritable • 3 inferences • Production of too many individuals leads to a struggle for existence • Struggle is not random, those that inherit best traits for environment are more likely to survive and reproduce (Darwinian Fitness) • Unequal ability to survive and reproduce leads to a change in a population (adaptation of a population)

5. Evidence of evolution • Taxonomic categories • Artificial selection • Homology-similar structures due to decent with modification • Anatomical Homologies(fig 22.14) • Homologous structure • Same structure, different function • Vestigial structures • Vs. analogous structures • Different structure same function • Embryological homologies • Molecular homologies • Compare DNA or proteins

6. Biogeography • Geographic distribution of species • Those located closer probably are related • Island biogeography show many endemic plants and animals • Fossil Record • Example of natural selection • Pesticide resistant insects • Drug resistance bacteria/viruses

7. Ch 23. Population Genetics

8. Hardy-Weinberg theorem • Frequency of alleles in a gene pool remain constant over generations unless acted on by agents other than Mendelian genetics. • Assumptions • No Gene Flow (migration) • No net mutations • Random mating • No natural selection • Very large populations • Small population can show genetic drift by chance, bottle-neck effect, or founder effect

9. Hardy Weinberg equation • p2 + 2pq + q2 = 1 • p = frequency of dominant allele • q = frequency of recessive allele • p + q =1 • Microevolution-the study of allele frequency from one generation to another

10. Preserving Genetic Variation • Polymorphisms • 2 distinct characteristics are both in high percentages in population • Nucleotide diversity (0.1%, or 1/1000 differences) • Geographic variation • Cline-gradual change in phenotype based on environment • Could be caused by both environment and genetic • Mutation and migration • Sexual recombination (recombination and independent assortment) • Diploidy (always heterozygotes) • Balanced polymorphisms • Heterozygote advantage • Frequency-dependent selection • Neutral Variation (no selection for or against)

11. Types of natural selection • Directional Selection • Favors one extreme form of trait • Stabilizing selection • Favors the average form (kills both extremes • Diversifying (disruptive) • Favors both extreme forms of the trait • See fig 23.12

12. Sexual selection • Sexual dimorphisms • Secondary sex characteristics not associated with reproduction or natural selection (peacock) • Natural selection does not fashion perfect organisms • Evolution is limited to modifying existent structures • Adaptation are often compromises • Some evolution is based on chance and not adaptations • There is typically no perfect variant

13. Ch 24 Origin of species

14. Speciation-creation of new taxonomic group • Species • Biological species concept-a population whose members can interbreed and produce viable offspring • Ecological species concept-based on its ecological niche • Pluralistic species concept-factors defining species changes based on species • Morphological species concept-based on features • Genealogy species concept-based on genetic history

15. Isolating mechanisms • Prezygotic • Habitat Isolation • Behavioral isolation • Temporal isolation (time) • Mechanical isolation • Gametic isolation • Postzygotic • Reduced hybrid viability • Reduced hybrid fertility • Hybrid breakdown • First generation is viable, but not second

16. Modes of speciation • Allopatric speciation • Geographic barriers can lead to origin of species (i.e. islands, rivers, mountains) • Geographic isolation has to be followed by a reproductive barrier • Adaptive radiation • Formation of new species from common ancestor based on different environments • Sympatric speciation • New species give rise within parent population • Can be due to polyploidy (such as plants) • Allopolyploidy-2 different species contribute to polyploidy • Animals typically will need a change in habitat or mating preference within same geographic area

17. Tempo of speciation • Gradualism • Speciation occurs slowly with minor changes in morphology • Punctuated equilibrium • Speciation occurs in rapid burst with long periods of no change • Exaptation-structure that evolves in one environment, but then is used for a different purpose in another environment

18. Ch. 25 Origin of Life

19. History of Life • Life starts 4 billion years ago • Prokaryotes evolve 3 billion years ago • Photosythesis evolved 2.7 b.y.a. (oxygen) • Started with bacteria and then chloroplast evolved • Eukaryotes evolve 2.1 bya • Endosymbiont theory • Chloroplast and mitochondria were once prokaryotic cells that joined other cells • Both chloroplast and mitochondria have prokaryotic DNA • Multicellular eukaryotes evolved 1.2 bya • Animal explosion during Cambrian period (543 mya) • Animals colonize land 500 mya

20. Origin of Life • Spontaneous generation-life can come from inanimate material • Louis Pastuer disproved theory in 1862 with flasked and broth (fig 26.9) • Biogenesis theory-life from life

21. Abiotic synthesis of organic molecules • First hypothesized by Oparin in 1920 • Tested in 1952 by Miller and Urey • taking water, hydrogen, methane, and ammonia and adding electric spark, you can form amino acids • our oxygen prohibits spontaneous formation of molecules • Other theories of molecules from space exist as well • Using Heat can build larger macromolecules • RNA might have been first genetic material • Protobionts (Protocell)-interaction of molecules to form higher level of order (cell-like) • Had membrane and could perform osmosis and diffusion • Probably could not replicate well or go through protein synthesis

22. Ch 26 Phylogeny and Systemics

23. Phylogeny-the evolutionary history of species • Uses the fossil (found in sedimentary rock) to place and date species • Dating Fossils • Relative dating • Using the series of rock layers to determine what order the fossils lived • Absolute dating (radiometric dating) • Using the radioactive isotope of known chemicals half-life to determine age of fossils • Shown evidence of plate tectonics and Pangaea • Shown that there has been a few mass extinctions throughout time (5 mass extintions pgs 521-523) • Fossils are very poor chronicle of the history of life.

24. Systemics • Taxonomy-naming and classifying organisms • Kingdom, Phylum, Class, Order, Family, Genus, Species. • Binomial name is genus and species. • Make phylogenic trees by cladistics (fig 25.80) • Cladistics analysis • Cladogram-phylogenic diagram of one group • each branch point represents divergence from a common ancestor • Some scientist want to redue classification system based on phylogenetic trees (PhyloCode) (ex. birds and lizards) • Each branch is called a clade • Clades should be monophylic • The ancestor and all of its descendents • See fig 26.10

25. Constructing cladograms • Sort homologous structures from analogous structures • Analogous structures represent convergent evolution • Identify shared primitive traits vs. derived traits • Shared derived traits are more important in showing relationships • Use an outgroup to compare with ingroups • Outgroup-organisms less related to all others that we are studying (won’t have the primitive traits) • Using a character table allows us to compare species traits • See fig 26.11 • Recently have used molecular systemics • Each mutation signifies a change • Molecular clocks-Can use the rate at which DNA mutates to determine age • Use the least number of changes to determine phylogeny (figs 26.14 and 26.15) • Parsimony (Occam’s razor)