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Ability to pass your genes on, or reproductive success.
The classical trick question gives you an individual who is strong, healthy, long-living, but does not reproduce. In this case, no matter how good the other traits are, if the individual does not reproduce, then it has a fitness of zero. |
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| selection by differential reproduction |
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Individuals who reproduce more viable offspring are selected for.
Individuals who reproduce less viable offspring are selected against. |
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| selects for a trait on one extreme. For example, selection for height of canopy trees in a rainforest: trees compete for sunlight, so selection favors trees to become higher and higher. |
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| selects for a trait that is moderate, and selects against the extremes. For example, birthweight: too low birthweight means that the baby is premature, too high birthweight means that the mom will have a hard time delivering, so there's a "just right" birthweight that is selected for. |
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| selects for the extremes. For example, birds occupying a habitat with 2 distinct niches (eating berries for a living and eating seeds for a living): small beaks are selected for eating berries, large beaks are selected for cracking seeds, medium beak is left out. |
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Natural selection acting on the group, not the individual.
Altruism sacrifice the fitness of the individual to benefit the group (family), which shares similar genes with the individual. When the benefit outweighs the cost, the altruistic behavior is selected for. |
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Increase in percent representation in the gene pool of the next generation
If the frequency of an allele increased, then that's evolutionary success for that allele.
If the frequency of alleles of an individual increased in a population, then that's evolutionary success for that individual. |
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Increase in percent representation in the gene pool of the next generation
If the frequency of an allele increased, then that's evolutionary success for that allele.
If the frequency of alleles of an individual increased in a population, then that's evolutionary success for that individual. |
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Three conditions for biological species
Be able to interbreed.
Be able to produce fertile, viable offspring.
Does this naturally.
Speciation is the formation of a new species. This can occur due to barriers to successful interbreeding within an initial species. |
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| Polymorphism is just a fancy word for different forms of alleles/traits. |
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| genetic change in a population caused by natural selection. |
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| Adaptation of traits to better fill a niche. |
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| Resources species use to survive in its environment. |
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Two species can avoid competition and better use the environment's resources.
Specialization occurs to better occupy a particular niche. |
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| Concept of population growth through competition |
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Population growth is checked by competition.
When resources get scarce, competition increases, which slows down population growth.
Competition within a species can force members within the species to occupy different niches, which drives speciation. |
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Inbreeding is mating between relatives.
Inbreeding increases the frequency of homozygotes, decreases heterzygotes, and decreases genetic diversity.
Inbreeding depression occurs because of the increase in the frequency of homozygous recessive detrimental alleles.
Some species (naked mole rats) naturally inbreed because:
They stay in one small area and don't migrate much.
Detrimental homozygous recessive alleles are eliminated because of many generations of natural selection. |
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Outbreeding is mating with non-relatives, which is just the opposite of inbreeding.
Outbreeding increases heterozygosity. |
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| bottlenecks, genetic drift |
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A bottleneck is a severe reduction in population size. This can be caused, for example, by a natural disaster that wipes out a majority of the population.
Genetic drift is the random changes in allele frequencies.
The effect of genetic drift increases as population size decreases.
Bottlenecks increase the effect of genetic drift. |
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Same lineage, evolving apart to be more different.
For example, bats and horses. Both share the same lineage as mammals, but the limb of the bat became wings while the horse developed hooves.
Divergent evolution produces homologous structures (bat's wing and horse's hoof). |
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Same lineage, evolving closer together to be similar, using similar mechanisms.
For example, the feeding structure in different species of crustaceans. The feeding structure came from mutation of pair of legs, turning them into mouth parts. This is a prime example of parallel evolution: same lineage, similar traits, evolved from similar mechanisms/mutations. |
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Different lineage, evolving closer together to be similar, using different mechanisms.
For example, bats and butterflies. Both have wings, but they came from totally different lineages, evolved through different mechanisms/mutations. Convergent evolution produces analogous structures (bat's wing and butterfly's wing). |
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Two species evolve in response to each other.
For example, predator/prey or host/parasite species.
Not yet an official MCAT topic, but many students confuse parallel evolution with coevolution. |
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Relationship where one benefits (parasite), and the other is harmed (host).
For example, worms living inside animal intestines. |
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Relationship where one benefits, and the other is not affected.
For example, some plants seeds disperse by sticking to animal fur. |
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Relationship where both species benefit.
For example, lichens are made from a mutualistic relationship between fungi and algae. The fungus provides anchor/absorption, and the alga provides photosynthesis. |
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| development through the life of an organism. |
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| development through evolutionary time of lineages/species |
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| vertebrate embryos share similar features |
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Gill slits
Notochord
Segmentation
Paddle-like limbs |
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| recapitulates phylogeny is the idea that the development of an organism repeats the evolutionary history of its species; starting with the fish-like common ancestor, which then changes to the modern form as development continues to adulthood. |
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