Biology Vocab and Key Concepts for Chapter 16 Evolution of Populations
Terms
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- gene pool
- combined genetic information of all the members of a particular population
- relative frequency
- the number of times that allele occurs in a gene pool compared with the number of times other alleles occur
- single-gene trait
- controlled by a single gene that has two alleles
- polygenic trait
- often has two or more alleles
- What two processes can lead to inherited variation in populations?
- the two main sources of genetic variation are mutaitons and the genetic shuffling that results from sexual reproduction
- How does the range of phenotypes differ between single-gene traits and polygenic traits?
- The number of phenotypes produced for a given trait depends on how many genes control the trait.
- directional selection
- individuals at one end of the curve have higher fitness than individuals in the middle or other end; evolution causes an increase in the number of individuals with the trait at one end of the curve
- stabilizing selection
- the curve have higher fitness than individuals at either end of the curve; keeps center of curve same but narrows overall graph
- disruptive selection
- individuals at the upper and lower ends of the curve have higher fitness than individuals near the middle; selection creates two distinct phenotypes
- genetic drift
- random change in allele frequency
- founder effect
- situation in which allele frequencies change as a result of the migration of a small subgroup of a population
- Hardy-Weinberg principle
- states allele frequencies in a population will remain constant unless one or more factors cause those frequencies to change
- genetic equilibrium
- allele frequencies remain constant; if no change then they don't evolve
- describe how natural selection can affect traits controlled by single genes.
- natural selection on single-gene traits can lead to changes in allele frequencies and thus to evolution
- describe three patterns of natural selection on polygenic traits. which one leads to two distinct phenotypes?
- natural selection can affect the distributions of phenotypes in any of three ways: directional selection, stabilizing selection, or disruptive selection. disruptive selection
- how does genetic drift lead to a change in a population's gene pool?
- in small populations, individuals that carry a particular allele may leave more descendants than other individuals, just by chance. over time, a series of chance occurrences of this type can cause an allele to become common in a population
- what is the Hardy-Weinberg principle?
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Five conditions are required to maintain genetic equilibrium from generation to generation:
-there must be random mating; -the population must be very large;
-and there can be no movement into or out of the population, -no mutations,
-no natural selection - speciation
- formation of new species
- reproductive isolation
- when the members of two populations cannot interbreed and produce fertile offspring
- behavioral isolation
- when two populations are capable of interbreeding but have differences in courtship rituals or other types of behavior
- geographic isolation
- two populations are separated by geographic barriers such as rivers, mountains or bodies of water
- temporal isolation
- two or more species reproduce at different times
- how is reproductive isolation related to the formation of new species?
- as new species evolve, populations become reproductively isolated from each other
- what type of isolating mechanism was important in the formation of different Galapagos finch species?
- speciation in the Galapagos finches occurred by founding of a new population, geographic isolation, changes in the new population's gene pool, reproductive isolation and ecological competition.