Evolution Notes and warm ups

Cell Phones

Evidence for Evolution Lets first make sure we are on the same page – Organisms do NOT evolve….populations do – Evolution does NOT explain where life came from, just why populations change – The mechanism of evolution is Natural Selection (so when I say either term….I mean the same thing)

Lamarck’s BAD IDEA

Cut the tail off of a female and a male mouse Breed the mice What are the chances that the offspring will not have tails?

Two kinds of Evolution Macroevolution Change above a species level New characteristics such as feathers Most of the events on our timeline represent Macroevolution Microevolution Change at the species level Change in a population from generation to generation Give some examples of microevolution?

Natural Selection Is a process and can be divided into five steps – Genetic variation--all populations have genetic diversity that gives them individual combinations of traits – Overpopulation—all populations compete for limited resources due to over reproduction – Environmental change—all environments are dynamic – Differential Reproduction (Survival of the “fittest”)—when environments change, the best adapted members of the population survive and reproduce – Population change—the genes of the reproducing organisms (and thus the traits) increase in the population

Natural Selection Adaptations do not happen in response to change….. Adaptations are already present in the population and make the organisms MORE SUCCESSFUL in the NEW environment For example: there are brown bears and white bears….if there is another ice age which will be best adapted?

Natural Selection Simulation Genetic variation-- we will model a variety of different modes for nutrient acquisition Overpopulation—we will compete for limited resources Environmental change—all sources of nutrition destroyed except for one Differential Reproduction—only those of you who can collect AND eat 5 “nutrient nodules” survive and reproduce (save the wrappers as evidence) Population change—those of you who survive get to pass on your traits

Natural Selection CAN NOT produce perfect organisms because…. Selection can only edit existing variation Selection is limited by environmental change…which is always changing Adaptations are often compromises– best solution for the least energy Chance, selection and the environment interact

Increase Genetic Variation Mutations (point and chromosome) – Only passed on if they affect the gametes – Only source of NEW alleles – Most mutations are HARMFUL Sexual reproduction – Crossing over (20,000 genes in the human genome) – Independent assortment (2 23 possible combinations) – Random Fertilization (2 23 X 2 23 possible combinations) Prokaryotes – Conjugation – Transformation – Transduction Gene Flow – Immigration – Emigration – Migration

Decrease Genetic Variation Small populations – Fixed genes – Isolation (geographic or genetic) Differential reproduction – Sexual selection (peacocks, rams) – Self pollination/self fertilization Asexual reproduction Low mutation rate Gene Linkage Groups

Genetic Variation Why is genetic variation important? What would happen to a population if the environment changes but they have NO variation? Low genetic variation is usually caused by fixed alleles– meaning that all organisms are homozygous for that trait.

Speciation Jig Saw Founder effect Bottleneck effect Gene flow Prezygotic barriers Postzygotic barriers Habitat isolation Behavioral isolation Temporal isolation Mechanical isolation Gametic isolation Reduced hybrid viability Reduced hybrid fertility Hybrid breakdown Polyploid speciation Adaptive radiation Genetic drift

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