* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
Download Document
Survey
Document related concepts
The Selfish Gene wikipedia , lookup
Punctuated equilibrium wikipedia , lookup
Mate choice wikipedia , lookup
Evolution of sexual reproduction wikipedia , lookup
Sociobiology wikipedia , lookup
Hybrid (biology) wikipedia , lookup
Hologenome theory of evolution wikipedia , lookup
Reproductive isolation wikipedia , lookup
The eclipse of Darwinism wikipedia , lookup
Natural selection wikipedia , lookup
Microbial cooperation wikipedia , lookup
Evidence of common descent wikipedia , lookup
Saltation (biology) wikipedia , lookup
Sexual selection wikipedia , lookup
Transcript
Evolution Notes Puzzle of Life’s Diversity A. Darwin 1. author of “On the Origin of the Species” 1859 2. theory of evolution (‘descent with modification’) and natural selection 3. evidence was found in: a. paleontology (fossil record) – shows gradual changes and mass extinctions b. biogeography – comparing and contrasting the distribution of organisms on different continents and observing their similarities of adaptation c. comparative morphology – i. homologous structures: body parts that resemble each other in form and structure (ex. bones of a whale fin, bat wing, human arm) ii. analogous structures: body parts that resemble each other because they are adaptations to similar environments (ex. shape of penguin, shark, dolphin) d. embryology – comparing similar stages of development to establish evolutionary relationships (Post-Darwin) e. molecular biology – examining DNA, RNA, amino acids, and proteins to estimate evolutionary divergences I. B. Main factors that increase species diversity: 1. mutations a. additions, deletions, and substitutions may be neutral, harmful, or helpful b. culling won’t eliminate unwanted traits 2. gene shuffling & crossing over during sexual reproduction 3. gene flow –immigration into a population 4. variation increases fitness, or the likelihood that a species will survive in changing environmental conditions C. Evolution: 1. Macro – major events changing life on earth as shown by the fossil record; patterns and rates of change among populations over time 2. Micro – small changes in genes, chromosome, and allele frequencies in a population II. Natural Selection A. Differences in survival and reproduction among individuals in a population that differ in heritable traits B. Individuals with higher fitness (superior phenotypes) will survive, reproduce, and pass their genes onto their offspring; while those with inferior traits are selected against. C. How Selection Acts Upon Populations: 1. Directional Selection: environment favors traits that are at ONE extreme of a range of traits a. Ex. peppered moths in Manchester, England b. humans artificially select crops for agriculture and animals for breeding which accelerates this 2. Stabilizing Selection: intermediate forms of a trait have high fitness while the extremes are selected against Ex. birth weight/size of organisms 3. Disruptive Selection: environment favors both extremes of a trait (opposite of stabilizing selection) Ex. finches feeding on hard and soft seeds 4. Sexual Selection: non-random mating where male competition and female choice lead to traits/behaviors that are selected for. small large Speciation – formation of a new species; genetic divergence A. Species – a group of individuals capable of interbreeding and producing fertile offspring B. Reproductive isolation – when members of two populations can no longer interbreed and produce fertile offspring because of 1. Prezygotic barriers: i. Allopatric speciation – physical barriers such as rivers, mountains, or bodies of water separate populations preventing gene flow; eventually causes speciation ii. Sympatric speciation – formation of a new species w/o physical barriers a. Behavioral isolation – differences in courtship rituals or other behaviors prevent possible interbreeding of species b. Temporal isolation – species reproduce at different times c. Mechanical isolation – genitalia is incompatible d. Ecological isolation – one habitat may have 2+ microenvironments e. Gametic mortality – molecular differences prevent hybridzation 2. Postzygotic barriers prevent the successful development of hybrids after a zygote forms IV. The Hardy-Weinberg Principle: allele frequencies within a population will remain in equilibrium if A. there are no mutations B. the population is large C. no emigration or immigration D. mating is completely random E. all individuals are reproducing equally (no nat. select.) equation: p frequency of: AA 2 + 2pq + q Aa 2 = 1 p = frequency of the dominant (A) allele aa q = frequency of the recessive (a) allele In a sample population: 1st generation 490 homozygous dominant butterflies 90 homozygous recessive butterflies 420 heterozygous butterflies th 10 generation 1470 homozygous dominant butterflies 270 homozygous recessive butterflies 1260 heterozygous butterflies Is the population evolving?