ch 23 Flashcards
(18 cards)
homology
characters in different organisms that are similar because they were inherited from a common ancestor that also had that character
microevolution
small genetic changes in a population
a change in frequency of a SINGLE alleledue to selection
population genetics
the study of how populations change genetically over time
population
a localized group of individuals capable of interbreeding and producing fertile offspring
gene pool
various alleles at all the gene loci- how many of each allele are present in a population
described in terms of genotype and allele frequencies
hardy weinberg theorem
describes a population that is in equilibrium from generation to generation
not evolving
frequencies of alleles in a population’s gene pool remain constant from generation to generation
tells us that sexual reproduction alone cannot bring about a change in genotype and allele frequencies of a pop
five conditions that keep a hardy-weinberg equilibrium
no mutations
no gene flow - no migration in or out
randomly mating - individuals pair by chance (not based on genotypes or phenotypes
no genetic drift - population is large and changes in allele frequencies are due to chance alone
no selection - selective forces don’t favor one genotype over another
what is the significance of the hardy-weinberg equilibrium
if the population isn’t in equilibrium then it is evolving.
the H-W tells us which factors caused the evolution
hardy weinberg equation
p^2 +2pq + q^2 = 1
p^2 = frequency of AA genotype
2pq = frequency of Aa
q^2 = frequency of aa genotype
p+q = 1
what two processes produce the variatio in gene pools that contributes to differences among individuals
mutation
sexual recombination
mutation
changes in the nucleotide sequence of DNA
causes new genes and alleles to arise
three major factors alter allele frequencies and bring about most evolutionary change
natural selection
genetic drift
gene flow
natural selection
differential success in reproduciton
resuklts in certain alleles being passed to the next generation in greater proportions due to more successful reproduction
genetic drift
the smaller a smaple, the greater the chance of deviation from predicted results
describes how allele frequencies fluctuate unpredictably from one generation to the next
bottleneck effect
sudden change in the environment may drastically reduce the size of a population
small sample of a population that may no longer be reflective of the original population’s gene pool
founder effect
occurs when a new colony is started by a few members of the original population.
reduced genetic variation
gene flow
consists of genetic additions or subtractions from a population
tends to reduce differences between two populations over time
why can’r natural selection make perfect organisms
evolution is limited by ancestral constraints
adaptations are often compromises
selection can only edit existing variatins.
