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Microevolution and Macroevolution

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adriana bass

on 15 March 2013

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Transcript of Microevolution and Macroevolution

evolutionary change at or above the level of species Microevolution
Small scale evolution, changes in allele frequencies in a population level Genetic drift Changes in the gene pool of a population (smaller the better) Bottleneck effect: an event that drastically reduces the size of the population. Ex: natural disasters can be the cause of this Founder effect: colonization of a new location by a small number of individuals ex. fingers Population: group of the same species living in the same place at the same time

Evolution: change in species over time

Gene Pool: all of the genes found in a population Terms to know: Gene Flow The movement of individuals or gametes b/ween populations Gene flow can:
alter allele frequencies in a population
reduce differences b/ween populations Natural Selection N.S is the only mechanism that consistently leads to adaptive evolution best adaptive individuals have most reproductive success; this results in traits that adapt a population to its environment Terms to know: Adaptation: inherited traits that enhance fitness (REMEMBER NOT ALL TRAITS ARE ADAPTATIONS)

Fitness: how able one is to pass genes on (reproductive success) How natural selection can alter variation in a population: Stabilizing Selection: the middle is favored. ex: sickle cell heterozygotes
Directional Selection: One extreme is favored.
Disruptive Selection: Both extremes are favored, not the intermediate Sexual Selection preference of who one wants to mate with, (females choose who to mate with because they have a specific number of eggs they are born with so they want to make good use of them Balancing Selection Allows two or more phenotypic forms in a population balancing selection can come from:
Heterozygote advantage
Frequency- dependent selection
Neutral variation Ways to define a species 1)Taxonomy: field of biology that studies the classification of species 2)The Biological Species Concept: whether organisms can mate and produce viable and fertile offsprings 3) Morphological species: physical apperance 4) Ecological species: organisms that are different because of different ecological roles 5) Phylogenetic species: uses evolutionary history Prezygotic barriers Temporal isolation: ex. nocturnal animals and animals who funcion during the day
Habitat isolation: ex. a snake living in water and one on land
Behavioral isolation: ex. the dance the blue footed boobie dance to mate with the female
Mechanical isolation: ex. snail shells, spirals need to go the same way to mate
Gametic isolation: ex. red and purple sea urchins' egg and sperm cannot bind to one another Postzygotic barriers Reduced hybrid viability: offsprings don't survive Reduced hybrid fertility: None fertile offspring Hybrid breakdown: hybrids would not survive because they are unhealthy Are prezygotic barriers or postzygotic barriers more harmful? Question: Allopatric Speciation: -formation of species
-geographic isolation leads to specification Ex. squirrel on different sides of the grand canyon Sypmatric Speciation polyploidy: occurs mostly in plants, self fertilization, they have many copies of chromosome Reproductive barriers: can occur when populations diverge. ex: fruit flies will mate with those that experienced the same environment as them. maltose fruit flies with maltose fruit flies, starch fruit flies with starch fruit flies Adaptive Radiation species diversify when there's a change in environment ex. Galapagos finches Coevolution occurs in response to a change in the environment this could be beneficial or non beneficial

result of one organism changing to change the other Mutualism: positive/ positive relationships
parasitism: positive/ negative relationships
Commensalism: positive/ neutral relationships Slow or quick speciation: Punctured equilibrium model: periods of no change punctuated by periods of rapid change. ex: fossils Gradualism model: gradually changing species. ex: natural selection
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