Chapter 19 Flashcards
loss of alleles within a population, purely by chance
genetic drift
a reduction in genetic variation when a subset of population sets up a new colony
founders effect
natural events get magnified-makes effect of genetic drift larger
bottleneck effect
genetics
genotype
what it looks like
phenotype
phenotypes produced by combined effects of 2 or more genes
continuous variation
what gives rise to genetic diversity among offspring?
random assortment of chromosomes, crossing over, random fertilization
loss of chromosomes
deletions
copy is made of chromosomes
duplications
uneven crossing over of non-homologous chromosomes
chromosome translocations
a group of interbreeding individuals in the same area, somewhat isolate from other groups
the population
all the alleles of all the genes in a population
gene pool
% of each genotype in the population
genotypic frequency
% of each allele in the population
allelic frequency
if a large population reproduces sexually at random, then the genetic frequencies should not change in the next generation and remains in equilibrium
hardy-weinberg equilibrium
conditions for hardy-weinberg equilibrium
- no mutations
- mating is random
- no selection (equal survival)
- very large population size
- no gene flow in or out (no immigration or emigration)
an evolving population is one that is showing genetic change over generation
change in allele frequency over time
microevolution
acts non-randomly on phenotypes of individuals, changes allelic and genotypic frequencies of populations non-randomly, always leads to adaptation of population to the current environment
natural selection
genetic frequency changes due to random events, often occurs in small populations
outcomes: random changes in allele frequency in either direction, often reduces diversity, one allele may become fixed, all others lost
genetic drift
alleles move in/out of the population
migration of adults, dispersal of gametes
Adds diversity to the population, reduces differences between populations, and increases survival under stressful conditions
gene flow
fitness is relative to other individuals in the population
Fittest= best reproductive success
relative fitness
shifts character’s mean value to one direction
directional selection
intermediates are less fit than extremes, maintains diversity
disruptive selection
intermediate types are more successful than the extreme, variation is reduced
stabilizing selection
success based on traits related to obtaining mates (and not directly related to the environment)
sexual selection
when girls and boys look different
ex: male cardinals are bright red to appeal to the females, which are brown in order to hide while laying eggs.
sexual dimorphism
