M1 Flashcards
prezygotic barriers
prevent mating or fertilization if mating occurs
postzygotic barriers
prevent hybrid zygote from developing into fertile adult or their offspring from reproducing
genetic incompatibilities maintain species boundaries
* some proportion of offspring are less fit
types of prezygotic barriers
- temporal isolation
- behavioral isolation
- mechanical isolation
- gametic isolation
- habitat isolation
- geographic
- ecological
reproductive barriers
- prezygotic barriers
- postzygotic barriers
habitat isolation
prezygotic barrier: occupying different habitats ➞ never come into contact
1. geographic: lions & tigers
2. ecological: diff levels of same habitat
* fish who live at diff levels of same lake
temporal isolation
prezygotic barrier: breeding at diff times
- ex: corals gametes dont come into contact b/c 1 hr diff in spawing
behavioral isolation
prezygotic barrier: do not recognize each other as potential mates
- mating calls or dances
- ex: fireflies’ light patterns
mechanical isolation
prezygotic barrier: physiological diff preventing copulation
- ex: dragonfliy genetalia or snail’s shell
gametic isolation
prezygotic barrier: sperm cannot fertilize egg
- species-specific protein recognition
- ex: purple & red urchin habe jelly coat surrounds egg w/ compounds that recognize specific proteins ➞ sperm needs specific proteins to enter coat & diff ones to enter egg
types of postzygotic barriers
- reduced hybrid viability
- reduced hybrid fertility
- hybrid breakdown
reduced hybrid viability
offspring don’t complete development or have low survivorship
- ex: yellow-belly & fire-belly toads’ hybrid offspring have low embryonic development & malformed jaws ➞ don’t eat ➞ cannot survive
reduced hybrid fertility
can make viable offspring but infertile
- ex: horse + donkey ➞ mule b/c diff # of chrom
hybrid breakdown
offspring are viable & fertile but their offspring are inviable or sterile
- ex: toad hybrid ➞ 75% survive backcross ➞ very few live to adulthood
- hybrid cross ➞ hatchlings but no tadpoles or adults
microevolution
w/in species ➞ changes in freq of gene variant across gen
- small-scale changes
- short time-frame
macroevolution
speciation ➞ accumulation of many microevolutionary changes resulting in new groups
* long-scale changes
* LONG time-frame (geographic time-scales)
taxa (taxon)
group of org on a phylogenic tree
sister taxa
most closely related on a phylogenic tree
* don’t assume that taxa close together are most closely related
branch point
where 2 diff taxa diverge on a phylogenic tree
clades
monophyletic clade
groups of taxa
a group that includes all taxa descended from a specific common ancestor
* can make 1 cut ➞ cut off 1 branch
speciation vs extinction
speciation: creating new lineages
* barrier to gene flow ➞ genetic divergence ➞ reproductive isolation
extinction: removing branches, loss of lineages
modes of speciation
- allopatric - vicariance
- allopatric - founder effect
- parapatric
- sympatric
allopatric speciation - vicariance
geographic separation into separate pop through physiological barrier means species cannot physically come into contact and no gene flow gives rise to new species
- ex: tectonic plates & penguins
- ex: oxbow lakes formations
allopatric speciation - founder effect
small group of indiv separate from original pop & become geographically separate ➞ pop diverge & become reproductively isolated
* ex: european starlings (geographical isolation)
* ex: snails on diff islands have opposite habddeness so cannot mate (mechanical isolation)
parapatric speciation
part of pop moves into new pop still connected to original pop
envir gradient
* envir gradient
* extension of range
* ex: zinc mine grass (habitat & temporal isolation)
* bird ring species can recognize neighbors mating call but not others’ (behavioral)
sympatric speciation
species diverge in same geographic location ➞ species ranges overlap
* new niche forms w/in pop & indiv in new niche diverge
* ecological habitat isolation ➞ ex: limnetic fish at diff levels of the lake
* insects on adjacent host plants
ex: hawthorn insect vs apple insects ➞ ecological isolation but also temporal isolation because diff fruiting time