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Bio 181 Speciation (macroevolution)

Terms in this set (33)

Species Concepts
How we define species
Species Latin for
"kind"
helps determine polarity of character of interest
a population or group of populations whose members are actually
or potentially interbreeding with one another but are reproductively isolated for other such groups
if 2 species cannot interbreed with each other they are sperate species.
Reproductive isolating mechanisms
any factor that impedes two species from
producing viable, fertile hybrids (3 kinds)
3 kinds of Reproductive isolating mechanisms
1. prezygotic
2. post zygotic
3. Reinforcement
Prezygotic isolating mechanism
impede mating between species or hinder the
fertilization of ova (happens before reproduction even occurs)
5 kinds of prezygotic isolating mechanisms
1. habitat
2. behavioral
3. temporal
4. mechanical
5. Gametic
Habitat isolation
→ two species or populations live in different habitats within a given area; encounter each other rarely
Behavioral isolation
special signals to attract mates differ. SPECIES SPECIFIC SIGNAL (mating call, songs, light production
Temporal isolation
→ two species breed at different times of day, different
seasons, or different years
don't even get the chance to interbreed because the timing is off.
Mechanical isolation
closely related species are anatomically
incompatible. (Parts don't fit) see this in plants a lot. Mechanically not possible to reproduce
Gametic Isolation
mating occurs, but fertilization does not occur
Environment is so foreign that the sperm can't survive.
Postzygotic isolating mechanism
fertilization occurs but something happens to
Zygote ( something goes wrong after fertilization occurs)
3 kinds of post zygotic isolating mechanisms
1. hybrid zygotę abnormality
2. hybrid infertility
3. Low hybrid viability
Hybrid zygotę abnormality
genetic incompatibility between two species
may abort development of hybrid at some embryonic stage
Hybrid infertility
production of offspring normal in every aspect
but being sterile (EX: Mule)
Low hybrid viability
c. Low hybrid viability → hybrids have lower survival.
Hybrid offspring just has something not right and it has low chances of survival, and they don't make it to reproductive age.
Reinforcement isolating mechanism
strengthening of prezyotic barriers. As populations diverge and differences build up, they reinforce any of these prezygotic mechanisms to become stronger and limiting the opportunity for interbreeding to occur
Speciation
the formation of new species
Microevolution is the mechanism for ___
Macroevolution
Allopatric speciation
speciation takes place in populations geographically separated
(a single population is separated by a physical barrier, and they may diverge enough to where they are distinct to where they are located and reproducing, if they come back together, cannot occur) (mountains and oceans are good barriers)
Sympatric speciation
speciation takes place in geographically overlapping populations
More common than we thought- (species evolving in the same area. Something else results in them no longer interbreeding so over time they become different) we see this among plants a lot.
Hybrid zones
areas of incomplete reproductive isolation- Where hybrids can form.
3 possible outcomes of hybrid zones
1. Reinforcement
2. Fusion
3. stability
Reinforcement (inn hybrid zones)
If hybrid offspring are less successful, complete reproductive
isolation may evolve through reinforcement
Strengthening the reproductive isolating mechanism.
Fusion
→ If hybrid offspring are successful, then the two populations would merge
again, and speciation would not occur

species comes back together again but this time they are still similar enough, so reproduction is possible, and their young are viable, and they fuse back together.
Stability
If hybrid offspring are only slightly disadvantaged, a narrow hybrid
zone may persist
Adaptive radiation
Relatively quick diversification of species from a single or a few ancestors
when introduced to a variety of new environmental opportunities
Endemic species
found in one location only
Coevolution
Cases where two (or more) species reciprocally affect each other's evolution
specific coevolution
"Evolution in two
species brought about by reciprocal selective effects between the entities"
diffuse coevolution
species may evolve in response to a number of other
species
Red Queen Hypothesis
each species has to run (evolve) as fast as possible just to stay in place -- because predators, competitors, and parasites also continue to evolve
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