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Biology-Evolution
Flashcards for chapter 16-evolution.
16
Biology
9th Grade
11/07/2011

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Term
gene pool
Definition
the combined genetic information of all the members in one population.
Term
relative frequency
Definition
the number of times an allele occurs in a gene compared to other alleles.
Term
single-gene trait
Definition
a trait that is controlled by a single gene that has two alleles.
Term
polygenic trait
Definition
a trait that is controlled by a gene that has two or more alleles.
Term
directional selection
Definition
when individuals at one end of the curve have higher fitness than individuals in the middle or at the other end
Term
stabilizing selection
Definition
when individuals near the center of the curve have higher fitness than individuals at either end
Term
disruptive selection
Definition
when individual at the upper or lower ends of the curve have higher fitness than those closer to the middle
Term
genetic drift
Definition
a random change in allele frequency
Term
what does the Hardy-Weinberg principle state?
Definition
allele frequencies in a population will stay constant unless one or more factors cause those frequencies to change
Term
genetic equilibrium
Definition
the situation in which allele frequencies remain constant
Term
what are five conditions required to maintain genetic equilibrium from generation to generation?
Definition
1)there must be random mating, 2)the population must be very large, 3)there can be no movement into or out of the population, 4)no mutations, and 5)no natural selection
Term
speciation
Definition
formation of new species
Term
reproductive isolation
Definition
when members of two populations cannot interbreed and produce fertile offspring
Term
behavioral isolation
Definition
two populations are capable of interbreeding but have differences in behavior
Term
geographic isolation
Definition
two populations are separated by barriers such as rivers or mountains
Term
temporal isolation
Definition
two or more species reproduce at different times
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