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SHSU BIOL 1308 - bio lecture notes

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Species: can and choose to breed with each other and no other species, produce viable offspringAllopatric Speciation: Other ; gene flow is interrupted or reduced when a population is divided into geographically isolated subpopulations; “Other country speciation”; the definition of barrier depends on the ability of a population to disperse** the greater the barriers subdivide a region, the greater the degree which speciation will occurSeparate populations may evolve independently through: MUTATION- not always bad, NATURAL SELECTION- who survives and who doesn’t & GENETIC DRIFT- randomness in nature (genetic variations)Randomness of events= more dramatic in smaller populations (genetic drift)Reproductive isolation may arise as a byproduct of genetic divergenceSurvives and passes on genes; stays in population- SELECTED FORDies and doesn’t pass on genes; taken out of population- SELECTED AGAINST (natural selection)Sympatric Speciation: Together; can overlap and interact; speciation takes place in geographically overlapping populations; can occur if flow is reduced by factors including: POLYPLOIDY, SEXUAL SELECTION, & HABITAT DIFFERENTIATIONPOLYPLOIDY: chromosome number is changing (going up); presence of extra sets of chromosomes due to accidents during cell division; much more common in plants than animals; can produce new biological species in sympatry with a single generationAUTOPOLYPOD- individual with more than two chromosomes sets derived from a single speciesALLOPOLYPOID: species with multiple sets of chromosomes derived from different species**takes a long time for randomness in nature to lead to sustainability of a species; TYPES OF NATURAL SELECTION:ARTIFICIAL SELECTION: humans are involved; start manipulating the ploidy of specific plants; humans involved in creating genetically modified organisms ALLOPATRIC SPECIATION: Has the same chromosomes and could interbreed, but they choose not to; want nothing to do with each otherDispersal- few members of a species move to a new geographical areaVicariance- natural situation (barrier) arises to physically divide organismsADAPTIVE RADIATION: start with one species and overtime it evolves into a lot of different species; always able to recognize on a cartogram; each has its own distinctive characteristics**SYMPATRIC SPECIATION:Speciation with the same physical location and conditionsArises from errors in chromosomes during cell divisionAneuploidy- two few chromosomesAutopolyploidy- two or more complete sets of chromosomes after divisions; results fromerrors in meiosisEnter another one here!!Genetic variability & environmental pressures- start the road to natural selection which leads to microevolution which leads to macroevolutionHybrids- either out-compete the original species; continue to be created for a long time; Fusion- two parental species made a hybrid; out-competing the two parents- arrow on slide should be purple (only one still around)Stability- hybrids continue to be producedReinforcement- fillGradual speciation- species diverge gradually through time with small stepsPunctuated equilibrium- species exhibits a large change in a relatively short period of time- no change for 100s of years and then the environment changes dramatically and randomlyDr Stephen J Gould – PEMicroevolution- changes in gene frequency above the gene level; before macroevolution*the more rapidly the environment changes, the more changes you’ll see in the natural world- different natural selection patternsMICROEVOLUTION leading to MACROEVOLUTION*** changes in the environment very quickly results in adaptive radiationPPT 2 CHAPTER 19:GENETIC DRIFT: the randomness in nature1. The chance events can cause allele frequencies to fluctuate. Nature is not teleological.“Fate” = Genetic driftDarwin’s Postulates (1859)The Theory of Natural Selection (Darwin 1859) – The 4 Postulates:1) There is variation among individuals within populations.2) At least some of the variations among individuals are hereditary (passed from parent to offspring).3) In every generation some individuals are more successful at surviving and reproducing than are others.4) Survival and reproduction are not random.- some individuals (those with favorable adaptations) tend to out-survive and out reproduce others (those that lack such adaptations)POPULATION GENETICS:1 : 2 :31 geneGene A2 alleles A= dominant allele a = recessive allele3 GentotypesAAAaAaFor every one gene there are two alleles and three genotypes. For now, this is how we will address population geneticsP + Q = 1 P = frequency of dominant alleleQ = frequency of recessive allele.P2 + 2PQ + Q2 = 1P2 = % of population that is genotypically homozygous dominant.2PQ = % of the population that is genotypically heterozygous.Q2 = % of the population that is genotypically homozygous recessive.ALLELE- different versions of the same geneDOMINANT ALLELE- codes for a functional proteinRECESSIVE ALLELE- if you get two recessive genes from your mom and dad; in theory should mean a decrease in fitness in the natural world; if your eyes are blue you lack the receptors to produce color; light effects them more negativelyAA and Aa transcribe and translate a “functional” protein. aa individuals do NOT transcribe and translate a functional protein for gene “A”; to wit, these individuals are going through life WITHOUT protein “A”. Blue eyes= example of natural selection going one way and sexual selection going another

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