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APY 107 (4)
Chapter 4

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University at Buffalo
APY 107
Niki Bertrand

The Forces of Evolution And The Formation of Species 04/04/2014 Forces of Evolution – factors that occur in natural population and changes in gene frequencies over multiple generations How Evolution Works Where does variation come from? Point Mutation – change in one base Chromosomal Mutation – large scale errors during replication we can get chromosomal mutation translocation, inversion, duplication How Natural Selection Works phenotypes gene ▯frequencies directional selection stabilizing selection – the average goes up and there are less on the extremes stabilizes population into the average stabilizing against any deviations from the extremes Gene Flow - the movement of genes between populations important because it can eliminate the harmful effect of inbreeding (when individuals with limited variation are breeding together ▯ harmful because it needs variation to survive) Genetic Drift – random changes in gene frequency in a population; the odds that genetic drift will have a profound change is greatest in very small populations Founder Effect – occurs when new populations migrate Ellis Van Crevald – type of dwarfism this particular founder group had this random change that was able to spread the population very quickly and become quite prevalent Genetic Bottleneck – occurs when a genetically diverse population undergoes a rapid reduction in size and increases again rapid reduction ▯ loses a large amount of variation examples: Elephant Seal – only 12 seals left ▯ lack of genetic diversity Sticklebacks – glaciers retreated and were stuck in pocketed lakes; one random mutation gave them the ability to survive and reproduce Sexual Selection: differential reproductive success among members of the same sex within species Animals mate non-randomly Male Struggle – to gain access to females Female Struggle – struggle by females to choose the right males female mate choice – driving force between certain male phenotypes sexual dimorphism – different in size between males and females runaway sexual selection – a males elaborate orientation may signal underline genetic health handicap principle – a male’s outlandish displays tell a female how vigorous they must be to survive EXAMPLE: peacocks ▯ large tails show that they are fit and why females should breed with them female can infer about these physical traits may choose a male for direct benefits (help raise offspring or with protection of predators) may choose a male for indirect benefits (for his genes) females have a limited reproductive offspring than males makes female a limited resource for the male females in turn have a much higher parental investment has to gestate, feed them, take care of them much more time commitment than the male Taxonomy and Speciation Systematics - used to understand evolutionary relatedness it classifies organisms based on a shared evolutionary history and do this by looking at similar features in related organisms Homologous – compare our arm to a whale’s fluke, you can see that our bones have homologous structures Analogous – it’s where some features are similar because of similar patterns of use; no shared ancestry Convergent Evolution – parallel Natural selection brought about similar form of function due to similar environments fennec foxes and artic foxes fennec foxes – desert foxes have huge giant ears artic foxes - tiny stubby ears species evolving due to its environment ancestral vs. derived derived – these are traits that species alone possesses which distinguish them from all other traits ancestral- from ancestors systematic biologists use these classifications to create phylogenic trees and the phylogenic trees are evolutionary histories of groups of related organisms Cladistics – certain traits are considered more evolutionary important and informative than others Cladograms – determine which traits are ancestral and which are derived doesn’t depict on time depicts relative degree of anatomical and evolutionary different Phenetics: numerical taxonomy – all similar traits to link two organisms together is not really used anymore clump organisms together regardless of homologous or analogous Law of Parsimony (Occam’s Razor) – the simplest solution tends to be the right one What is a Species? – dynamic and ever changing Species Concepts Biological – it defines species as interbreeding populations reproductively isolated from other such populations and refers to natural populations only Evolutionary – defines species as evolutionary lineages with their own unique identity Ecological – these species should occupy its own ecological niche that distinguishes it from all different species Recognition – defines species on unique traits or behaviors that allow members of spe
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