| What are the 3 different types of reproductive isolation? | temporal
behavioral
geographic |
| Why does speciation occur? | bec of divergence of isolated populations
it can be gradual or happen abruptly |
| What are different types of selection? examples? | directional
stabilising
disruptive |
| What are population bottlenecks? (4) | when an event greatly reduces the population size
can be natural (fires) or human induced (overhunting)
the remaining population will be smaller = less genetic variability
eg: overhunting northern elephant seals |
| What is the founder effect? | when a new population is made by a small subset of the larger population = less genetic variation + greater genetic drift |
| What are the 3 main types of selection? effect? | stabilizing: intermediate phenotype is favored over the extremes
directional: one phenotypic extreme is chosen
disruptive: both extremes are selected over the intermediate phenotype |
| What is reproductive isolation? what are the 2 types? | reproductive barriers emerge to keep 2 population from interbreeding = gene pools become separated
pre-zygotic: before fertilisation happens (no offspring)
post-zygotic: after fertilisation happens (infertile offspring) |
| what are the 3 pre-zygotic reproductive isolation types? examples? | temporal = diff period of activity and for reproduction
EG: leopard and wood frogs breed at diff times
behavioral = different courtship behaviors
EG: some birds only respond to specific mating calls
geographic = populations are in diff habitats within a region
EG: lions and tigers usually live in different habitats |
| what are the 3 post-zygotic reproductive isolation types? examples? | Hybrid unviability = fail to develop reproductive maturity
EG: some tadpoles die before maturity
Hybrid Infertility = the hybrids don't produce functional gametes
eg: mules are sterile
Hybrid breakdown = the 2nd generation of hybrids fail to develop properly
EG: offspring of hybrid copepods have lower survival potential |
| What is speciation? (5) | causes the formation of new species
happens when isolation barriers prevent gene flow bw 2 populations
= diverge due to genetic drift and natural selection
there are 2 types:
allopatric = divergence due to geographical isolation
sympatric = divergence in the same location |
| What is allopatric speciation? | geographical separation of population with a physical barrier
= exposed to different environmental conditions and diverge
eventually cant interbreed - speciation
eg: darwin's finches |
| What is sympatric speciation? | divergence of species in the same location
bec of difference in reproductive or behavioral isolation
eg: polyploidy in Allium |
| What is polyploidy? (4) | additional set of chromosomes if sex cells fail to undergo cytokinesis = abnormal zygotes
more common in plants bec they can self fertilise
reproduce asexually |
| What are the 2 models of speciation? | phyletic gradualism: from continuous change at a constant pace
gradual accumulation of genetic mutations over time
Punctuated equilibrium: from abrupt bursts bw periods of stability bec of rapid environmental changes |
| What is phyletic gradualism? evidence to support? | continuous divergence at a constant pace = speciation
supported by intermediate forms in the fossil record |
| What is punctuated equilibrium? evidence? | short evolutionary bursts bw stable periods
supported by gaps found in fossil records |
| What is the determination of speciation limited by? | certain organisms not reproducing sexually (bacteria)
breeding capacity is impossible to determine w fossils
physically impossible for certain members in a species to mate |
