Exam 4 part 1 Flashcards
gene frequency
allele frequency in a population
Hardy Weinberg assumptions
- infinitely large
- random mating
- no selection
- no migration
- no mutation
directional selection
favors one extreme or the other
- homozygotes favored
disruptive selection
favors both extremes
stabilizing selection
heterozygotes favored
genetic drift
random loss and fixation of alleles
founder effect
loss of genetic variation when a small population is created from a group leaving a larger population
bottlenecking
a drastic size reduction due to some environmental event causing a loss of diversity
assortative mating
mate based on phenotype
positive assortative mating
mating like individuals together
- more homozygotes
negative assortative mating
opposites attract
- more heterozygotes
inbreeding
changes frequency of genotypes but not allele frequency
- more homozygotes
non random mating changes …
frequency of genotypes but not allele frequency
evolution 2 step process
- genetic variation arises
- alleles increase or decrease in frequency in the gene pool
reproductive isolation
species can no longer exchange genes
prezygotic reproductive isolation
ecological, behavioral, temporal, mechanical, and gametic
ecological isolation
differences in habitat
behavioral isoaltion
differences in mating behavior
temporal isolation
reproduction takes place at different times
mechanical isolation
anatomical differences
gametic isolation
gametes are incompatible
postzygotic reproductive isolation
hybrid inviability, hybrid sterility, hybrid breakdown
hybrid inviability
hybrid zygote does not survive to reproduction
hybrid sterility
hybrid is sterile
hybrid breakdown
F2 is inviable or sterile
allopatric speciation
geographic barrier initiates speciation by blocking gene flow
allopatric speciation example
darwins finches (beak size)
sympatric speciation
a single interbreeding population without a geographic barrier
sympatric speciation example
apple maggot fly change in diet
