Evolution Flashcards
(22 cards)
genetic drift
chance fluctuation of genes from one generation to next
small populations affected more
founder effect
type of genetic drift
by random chance, a small group is separated by migration or isolation and a new population breeds to make different gene pool
bottleneck effect
type of genetic drift
natural disaster occurs and only a small population survives to reproduce
gene flow
movement of gene from one population to another
can help or hurt a population
genetic pollution
negative effect of gene flow
unwanted gene is introduced and reduces fitness to an environment (decreases gene pool)
directional selection
one phenotype is favored over another
seen with change in environment
ex. gray moth favored in smoggy city over white moth
disruptive selection
two different phenotype extreme are favored over anything in between
ex. cuddlefish: small males pretend to be female while large males mate
stabilizing selection
middle type is favored
ex. mice that are too dark or too light would stand out so middle gray color is favored
species
a group of individuals that can interbreed in nature and produce viable offspring
prezygotic barrier
means before zygote
- habitat isolation
- temporal isolation
- mechanical isolation
- behavioral isolation
- genetic isolation
habitat isolation
different habitats make it difficult to mate (they will not even interact)
temporal isolation
different mating seasons
mechanical isolation
physically unable to interbreed
ex. ducks
behavioral isolation
species specific courtship ritual
- males and females look physically different
ex. peacock dance + bright colors
genetic isolation
sperm of one species cannot fertilize eggs of another species
post zygotic barriers
means after zygote
- reduced hybrid viability
- reduced hybrid fertility
- hybrid break down
reduced hybrid viability
hybrid offspring is frail and cannot survive
reduced hybrid fertility
hybrids that can survive are sterile
ex. mule (horse x donkey)
hybrid break down
some first gen offspring are fertile but next gen are weak or sterile
speciation
the process by which one species splits into two or more species
- allopatric speciation
- sympatric speciation
allopatric speciation
gene flow is interrupted due to geographical isolation
ex. canyon splits in two
sympatric speciation
geographically overlapping population
- when gene flow is reduced
- habitat differentiation: specialize in different resources
- sexual selection: different mating preferences
