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| Evolution by Natural Selection |
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Definition
| 1. variation is 2. heritable and leads to 3. differential survival and reproduction |
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| genes play some role, but environment is also important |
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| idea that genes have absolute control |
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| Evolution is controversial |
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Definition
-emphasis on variation
-perfect type
-evolution is stochastic (blind)
-Probabilistic
-speciation
-conflicts with religion |
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Definition
| incorporates genes into natural selection |
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| Role of genes in behavior (examples) |
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Definition
Study mutants "knockouts"
-in drosophila, stuck males won't disengage (mating behavior alteration)
-dunce line learning deficiency) |
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| study populations with genetic differences, example: food preferences of inland vs coastal gardener snakes |
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Definition
| coastal only eats toads and fish, not banana slugs because they resemble leaches. coastal will eat banana slugs in lab. |
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Term
| condition dependent strategy (plus example) |
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Definition
environment triggers alternative development. ex tiger salamander larvae 2 kinds- normal and carnivorous. Related to body size, number of larvae in pond, and kinship.
ex. #2 spadefoot toad - carnivore vs omnivore
-dependent on # of shrimp in pool
-large number of shrimp means toads will be carnivorous, because carnivores have faster development so they can escape pool faster (before it dries up). |
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Definition
| outcome of a process, change in response to prevailing conditions |
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| physiological (acclimation) |
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| adjustment to new environment, no genetic change. heat, cold, altitude etc. |
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| trait favored by natural selection today, benefits organism now (example ducks have webbed feet, which is advantageous over ducks w/out) |
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| Evolutionary Origin of Trait |
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Definition
Trait evolved by N.S. in response to selective conditions and is currently maintained by n.s. for same reason
ex. penguins didn't evolve wings for swimming by they use them to swim, and they have been maintained because it is advantageous |
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| trait that confers current utility, high fitness today, but NO EVOLUTIONARY ASSUMPTION |
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| evolved for same reason it confers utility today |
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| trait that confers utility but evolved for some other reason |
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| adaptation for growth, exaptation for birth |
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does trait confer higher fitness?
-observe natural variation (this is really first a study of aptation)
-create/manipulate variation in the environment or the trait |
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| Same trait evolving in different organisms experiencing similar selective pressures proves that it is unlikely to be accidental, and instead that trait is adaptation to that environment. |
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Definition
| Different selective pressures lead to divergent behavior. Ex. Kittiwake vs Black-headed gulls. Kittiwakes have evolved cliff nesting as a result of a low predation environment, so we see no egg shell removal or next cleaning. |
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| similar selective pressures lead to similar shared behavior (across species!) Likely a result of CONvergent evolution ( |
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| similar as a result of INDEPENDENT adaptation to same or similar environmental conditions, leads to convergent evolution. Ex arctic animals have white coats. |
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| similar as a result of common ancestry, not independent adaptive events, so not more data points |
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| alternative adaptive peaks |
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| evolving different traits to solve same problem |
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| multiple solutions to same problem leads us to look for adaptations to problems that aren't there. Road side analogy, we don't want to run into each other so we pick a side of the road, but we didn't necessary have a reason for picking the right side! |
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| How do you identify adaptations? |
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Definition
-study natural selection
-design principles
-convergent evolution
-historical approaches (fossil records) |
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not all traits are adaptive
not all adaptive traits are perfect |
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Definition
genetic drift
founder effects
correlated consequences of selection for another trait (pleiotropy, genetic linkage)
-no genetic differences?
-historical legacy?
-gene flow
**functional equivalents |
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Definition
| we may see equivalent traits but that doesn't mean anything sometimes |
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| developmental constraints |
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Definition
| ex. skinks lose parts of their tail, adaptations occur proximally first |
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Definition
| can't reach optimality because evolution of existing design results in decreased fitness. Ex. Jet plane |
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*PRIMARY force for ev. change*
-selection for a higher or lower direction of a character
-nature's eq. to artificial selection
-measurable response (we can observe it)
-change in mean, not in variance |
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| Directional Selection examples |
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Definition
Bullfrog
-big male = advantage because correlation of chest cavity to croak (females want bigger males, more protection, more eggs etc)
*What about extended phenotype? we would also see that territory is an extended phenotype of the male |
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Definition
selection AGAINST phenotypes that deviate from optimal value of character
-no change in mean, but DECREASE in variance
-most traits under stabilization
EX. Jamaica Croacking Gecko
-large body = good for mating but dangerous for predation
Ex Birth Size
Ex clutch size and parental investment |
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Term
| Disruptive Selection (african seed cracker) |
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Definition
Selection for two or more modal phenotypes against those intermediate between them.
-important for speciation (rare)/ ev. change
Ex. Seed cracker
-bird with small or large beak, but not in the middle
-dominant recessive trait |
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| Frequency-Dependent Selection (positive or negative) |
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Definition
When the selective value of an allele is affected by frequency within population
-negative: when common has disadvantage, because predators form search images, deletion of resources, and "rare male advantage"
-positive: when common has advantage, because when you stand out you are more of a target, and when animals are brightly colored then common is good! |
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Definition
| Gene-> Individual -> kin -> Group-> species |
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Definition
-selfish gene theory: artificially increases a gene frequency w/in population. Doesn't seg. at meiosis.
-t allele
-fundamental unit of heredity = gene
-fundamental unit of selection |
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Definition
favor reproductive success of relatives over individual
-relies on inclusive fitness model
-important for explaining heritability of altruistic traits!!
-direct and indirect fitness |
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Analogous to individual selection on groups
-weak relative to individual selection
generally operates in concert with IS
-only in extreme cases would it be expected to work against IS |
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Definition
origin/extinction of clades (groups of species)
-macroevolutionary
-can't really explain individual |
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| Biological species concept |
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Definition
species are actually/ potentially interbreeding populations which are REPRODUCTIVELY ISOLATED from other such groups
-w/in locality, sympatric species are distinct entities
-across populations a species may differ, but maintains connectedness (due to hybrids? gene flow? breeding?) |
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| Post-mating reproductive isolation |
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Definition
gametic/zygote mortality
hybrid inviability
hybrid sterility (ex. mule) |
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| pre-mating reproductive isolation |
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Definition
-ecological (habitat or temporal): mates don't meet
-ethological (behavioral): different mating rituals. Ex = different boobies in the galapagos (blue footed, masked, red footed)
-mechanical (no behavioral component): they attempt but no sperm transfer |
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Definition
populations are separated geographically, then they become separate species
-no behavioral component |
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individuals are interacting and you never interupt gene flow, so how?
-instantaneous: something happens that immediately changes species, for ex. change in chromosome number
-gradual = behavioral = driving component |
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Definition
| two populations are sympatric if they are physically capable of encountering one another with moderately high frequency |
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energy maximization
-more energy = more offspring produced
ex. orb |
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Makes testable predictions
-if natural condition follows the model then you have identified the key factors influencing an organisms behavior (yay!)
-if not, you need to investigate other factors |
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Definition
1.) never eat anything bigger than your head
2.) eat items that lead to highest energy gain/ profitability
-profitability = energy gain/ time |
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| Profitable vs. unprofitable prey |
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Definition
animals CAN distinguish
ex. northwestern crows: feed on whelks, they choose bigger ones because when they drop them they are easier to break and give more food
-optimal flight height is 5 m (max energy gain) |
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| Distinctions in levels of profitability |
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Definition
| ex. oyster catchers: go for medium size mussels (30-40mm) because the big ones have a lot of barnacles and are difficult to open |
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(small energy gain/ handling time) is greater than > (large energy gain/ search + handling time)
-the key here is the abundance of more profitable item |
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Definition
1. acceptability of a food item depends on the abundance of the MORE PROFITABLE food item and not on its own abundance
2. when high-ranking items become more common, less profitable items will be eliminated from the diet |
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Definition
| birds will eat smaller food item when bigger food items are spaced further apart |
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Definition
| occurs when density of preferred food type increases |
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(energy not the only factor)
vitamins/minerals
-ex. moose require minimum daily Na. Water plants are low cal but high Na, so they will strike a balance in their diet combining Na intake with max energy |
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(another food choice constraint)
some high energy foods = high toxin
-dirt = toxin neutralizer
-ex howler monkey: the more common tree species they are less likely to feed on due to high alkaloid and tannium levels, which make it difficult to digest. New leaves have more water and are better, and monkeys feed wastefully, only eating the petiole (lower toxins there). |
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| Intraspecific competition |
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Definition
competition with the same species
-ex young bear might take a fish because the bigger bear will go after it |
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| Foraging and Biotic interactions |
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Definition
-Competition (again, intra and interspecific)
-predation: sometimes optimal foraging is too risky
-ex. barn feeder birds: they will feed individually inside barn, but feed in groups outside
-ex. manatees will not "excavate" as much as they could because stirring up dust makes them visible to sharks
-ex. wolf and elk: after wolf introduction there were less calves born in summer AND less calves surviving winter, meaning there were both direct and risk effects |
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Definition
| preference determined by e/(h+s), for each item the net energy return from searching and handling time |
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Definition
long handling time and short-ish search times
-ex lion
-you specialize as habitat improves
-ex. bears only eat energy rich parts of fish (eggs, head) |
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short handing time long search time
-ex insectivorous birds |
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highest number, and best supply of profitable food
-ex rats in lab have food stations with levers, they will go to station that gives bigger pellets
-ex. as you introduce more large worms, birds will become more specialized to eat large worms, but this doesnt happen right away |
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Definition
animals will continue to sample lower density areas why? because if that area suddenly changes then they have a back-up plan
-compromise? sampling costs
-animals will spend more time sampling as the quality of the site decreases
-ex. great tits and grids containing meal worms. birds quickly switched to the second highest prey density site. |
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Definition
chipmunks store food in cashes
-they will urinate on a site after it has been depleted so that they do not return
-reduces sampling costs |
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animals can LEARN from their previous sampling experiences
-they adapt their search behavior to match local environmental conditions
-ex. woodpeckers learn to adapt search behavior accordingly, by increasing or decreasing the number of holes they sample to match the optimal number of attempts |
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| why do we find animals in sub optimal patches? PERCEPTION |
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Definition
-foragers are unable to accurately perceive the measure of food abundance at a particular site
-Their information might be bad, and they havent been able to find the best site.
-They might not perceive the quality of sites correctly (their prey are camouflaged) |
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| sub-optimal patches LEARNING |
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Definition
| animal hasnt adapted to new environmental conditions |
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Definition
| model for how animals will settle into patches that accounts for differences in patch quality and competition from others |
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Patch Choice Model - Marginal Value Theorem
-when is optimal time to leave? |
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Definition
-Energy in patches shows diminishing return (meaning return rates diminish as forages collect resources from patch)
-forager should leave patch when resources are depleted to the point where other patches will yield higher energy (so when the avg. drops below the avg. of surrounding patches)
-this takes travel time into account |
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| So when thinking about moving...animals should consider |
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Definition
1. the abundance of food at current site relative to others around (avgs)
2. the difficulty or time it takes to get to another site |
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Definition
when animals bring food back to a specific site
-ex. starlings feed on beetle larvae and bring them back in their beaks. They will see diminishing gain curve because it becomes harder to probe as bill fills.
-The farther they travel the more they fill their beaks before returning home |
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