Term
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Definition
- Directional selection moves mean one direction or the other
- [image]
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Term
| How fast does evolution happen? |
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Definition
- when selection is strong
- heritability is high
- selected individuals very different than non-selected
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Term
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Definition
- reduces the amount of variation in a trait
- maintains mean
- decreases variance
[image] Ex: Galls in plants, and insects, birds |
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Term
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Definition
- increases amount of variation in a trait
- doesn't shift mean
[image] |
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Term
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Definition
- explains bizarre adaptations of males
- Bateman's principle: Female reproductive success typically limited by resources. Male R.S. limited by access to mates.
- [image]
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Term
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Definition
- size, color, etc differences
- Ex: elephant seals
- humans not very sexually dimporphic (~10%)
- sexual selection not relevant to humans necessarily
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Term
| 2 components of Sexual Selection |
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Definition
- male-male competition
- femae choice (to obtain best mate possible)
- nuptial gifts
- showy males
- bird/frog songs
- Coloration:
- used to display health
- takes energy to make pigments
- birds prefered uninfected birds with brighter beaks
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Term
| Assumptions of Hardy-Weinberg Principle |
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Definition
- no selection
- no mutation
- infinite population size
- no migration (movement between differing populations)
- random mating
NULL model allows us to study departures from assumptions |
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Term
| attacking H-W problems/frequencies |
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Definition
- calculate allele frequencies
- calculate observed genotype frequencies
- calc. expected genotype frequencies (p2:2pq:q2)
- compare observed/expected
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Term
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Definition
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Term
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Definition
Major Histocompatibility Complex |
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Term
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Definition
at DNA level "point mutations" at chromosome level gene duplication, etc
can change proteins can change gene regulation source of all variation minimal effects in short term 10-6 mutation rate per generation
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Term
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Definition
Alleles can be lost, without regard to phenotypic differences Effect is larger in smaller pops an allele is 'fixed' if it is the only allele left Drift can also lose good genes
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Term
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Definition
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Term
| 4th assumption: No migration |
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Definition
Migration is another name for gene flow among populations will change allele freqs within a population if the source pop differs in frequencies. Gene flow can cause homogenization of populations may explain why populations can't adapt to conditions at margin of species range
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Term
| Last assumption: Random mating |
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Definition
- Does not directly change p,q
- Does cause genotype frequencies to depart from p2:2pq:q2
- Non random mating could be
- diassortative: mates are more diff. than random
- assortative: mates are more similar than random
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Term
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Definition
- increases heterozygosity
- with MHC, variation could be maintained via disassortative mating (fish/mammals can detect MHC genotypes by smell)
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Term
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Definition
- If trait is heritable, increases homozygosity
- in extreme, could lead to speciation
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Term
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Definition
- form of non random mating
- (assortative mating)
- selfing
- increases homozygosity
- inbreeding depression = reduction of fitness due to inbreeding (caused by rare, deleterious, recessive alleles)
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Term
Mechanism and Impact on Variation - Selection
- Mutation
- Drift
- Gene flow
- non-random mating
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Definition
- Selection: increase, reduce, or maintain
- mutation: increase (original source of all variation)
- Drift: reduce
- Gene flow: increase w/in pop, reduce among pop
- non random mating: increase heterozygosity (disassortative). increase homozygosity (assortative)
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Term
Darwin's thoughts (never talked about origin of species!) |
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Definition
- Evolution as natural descent with modification
- natural selection as mechanism for adaptation
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Term
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Definition
- the divergence of a single ancestral species into 2 descendent species
- process responsible for all biodiversity
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Term
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Definition
- Morphological (looks different)
- Biological (reproductive isolation)
- Phylogenetic (a species is the smallest monophyletic group)
- looks for pattern of independent evolution
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Term
| Biological Species Concept |
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Definition
- focuses on reproductive isolation
- Prezygotic - prevents mating
- habitat (stickleback fish)
- behavioral differences (lightning bugs)
- genetic differences (sea urchins)
- Post zygotic -after mating
- progeny with low survivorship
- progeny with low fertility
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Term
| How Rep. Isolation established? |
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Definition
- Allopatric (different homeland) speciation, geographic isolation leads to reproductive isolation
- Dispersal - islands, etc
- vicariance - physical barrier divides species (ox bow in rivers)
- Sympatric - same homeland. can feed on different things (ie soapberry)
- (sometimes gene flow prevents divergence, even when selection would favor for different adaptations (banded, solid snakes)
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Term
| Sympatric speciation, cont'd |
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Definition
- polyploidy in plant also leads to sympatric speciation
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Term
| What happens when recently diverged species come into contact? |
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Definition
- Sometimes R.I. not complete, and fertile hybrids form
- ie. Townsend's warbler overtaking hermit warbler on West coast of North America
- example: sunflower = new hybrid species, unique combination of traits, withstands drier habitat than parental species, RI from both parents
- Humans create hybridization oppurtunities
- lose distinct species through hybridization
- ie. flicker (bird) 2 species--> 1
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Term
| Differentiation in human pops. |
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Definition
- all human populations are 99.9% similar (genetically)
- Most human diversity is in Africa
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