Campbell Biology: chapter 23 Flashcards
________ evolve while _______ do not.
Change in allele frequencies in a population over generations
What are the three min mechanisms that can cause allele frequency change?
Natural selection, genetic drift, gene flow
differences among individuals in the composition of their genes or other DNA segments
The average percentage of loci that are heterozygous
differences in the genetic compositions of separate populations
a graded change in character along a geographic axis
Consists of all copies of every type of allele at every locus in all members of its population
If only one allele exists for a particular locus in a population, that allele is said to be ____.
States that the frequencies of alleles and genotypes in a population will remain constant from generation to generation.
hardy Weinberg principal
what are the 5 hardy Weinberg conditions?
1.no mutations 2.random mating 3.no natural selection 4. extremely large population size 5. no gene flow
Chance events that can cause allele frequencies to fluctuate unpredictably from one generation to the next .
What are two examples of circumstances that can result n genetic drift?
fonder effect and bottle neck effect
When few individuals become isolated from larger population, this smaller group my establish a new population whose gene pool differs from the source population
Sudden change in the environment, such a fire or flood, may drastically reduce the size of a population.
the transfer of alleles into or out of a population due to the movement of fertile individuals or their gametes.
the contribution an individual makes to the gene pool of the next generation relative to the contributions of other individuals
occurs when conditions favor individuals exhibiting one extreme of a phenotypic range, thereby shifting a populations frequency curve for the phenotype character in one direction or the other.
occurs when conditions favor individuals at both extremes of a phenotypic range over individuals with intermediate phenotypes.
acts against both extreme phenotypes and favors intermediate variants.
A form of selection in which individuals with certain inherited characteristics are more likely than other individuals to obtain mates.
What can sexual selection result in?
Difference between the two sexes in secondary sexual characteristics
meaning selection within the same sex, individuals of one sex compete directly for mates of the opposite sex.
mate choice- individuals of one sex are choosy in selecting their mates from the other sex.
differences in DNA sequence that do not confer a selective advantage or disadvantage.
occurs when natural selection maintains two or more forms in a population
if individuals who are heterozygous at a particular locus have greater fitness than do both kinds of homozygous
the fitness of a phenotype depends on how common it is in the population