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17 Cards in this Set

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  • Back
Population
All the Ind. of a species that live in one place at one time
-people in Omaha
-people in the world
-ducks in Eastern Nebraska
-deer in a forest
Devil's Hole Pupfish
-Death Vally
-isolated area
-only population of this fish in the entire world
Demography
-statistical study of populations
-the environment's capacity to support the pop. limits its size
3 Key features of pop.
-pop. size
-small pop. more in danger
-pop. density
-number of ind. in a certain area
-a ratio:
-# of ind.
---------
area
-dispersion
-the way the ind. are arranged
population model
-hypothetical pop. that has the key characteristics of a real pop.
carrying capacity
-the pop. size that an environment can support
*R-strategists
-pop. that grow very fast (explosions) and die quickly
-some insects, annual plants, bacteria
-young get little or no care from parents
-young mature and grow quickly
*K-strategists
-whales, rhinos, redwood trees
-slow pop. growth, live in environments that are stable and predictable
humans
-many traits of k-strategists
-BUT have changed the environment to greatly increase "carrying capacity"
Hardy-Weinberg Principle
-1908
-pop. don't change unless evolutionary forces act upon them
-true only for large pop. in which ind. mate randomly and the forces that change the proportions of alleles are not acting
-it uses math to predict the frequency of each genotype in a pop. if you know the allele frequencies
5 forces causing evolution in pop.
-mutations
-changing of alleles, doesn't happen often
-migration
-movement of ind. from one pop. to another
-creates a gene flow (mixing of new genes and alleles)
-nonrandom mating
-when ind. mate w/ others of their own genotype
-inbreeding
-mating w/ relatives
-genetic drift
-in small pop.
-chance event (fire, flood) causes the frequency of alleles to change
-this (in past) has affected humans-we used to live in small, isolated groups or tribes
-natural selection
-causes deviations from the Hardy-Weinberg Princ. by directly changing the frequencies of alleles
How natural selection shapes pop.
-natural selection reduces the frequency of a harmful recessive allele slowly because very few ind. are homozygous recessive and express the trait
genetic polymorphism
-when a gene in a pop. has more than one allele appearing at a significant frequency
-look/read fig 15-5 on p.337
polygenic trait
-a characteristic influenced by several genes
-human height
-often results in a normal distribution
directional selection
-when selection acts to eleminate one extreme from a range of phenotypes
-the genes promoting this extreme become less common
stabalizing selection
-when selection acts to eliminate extremes at both ends of a range of phenotypes
-increases the number of ind. that are similar
disruptive selection
-when selection acts to eliminate rather than favor the "average"
-the pop. will have larger numbers of ind. at the 2 extremes