Theme 4c Pt 2 Flashcards
What is speciation? What does it cause
Process in which new species arise, this causes biodiversity
What is the study of speciation made of
Combines study of ecology evolution and genetics
And links macro and microevolutionary processes
What causes genetic divergence between populations
Drift
Founder effect and bottleneck
Mutation
Differential selection (natural, sexual)
What are the two types of reproductive isolation
Prezygotic mechanisms
Postzygotic mechanisms
What are prezygotic mechanisms give examples
They prevent mating or fertilization
Habitat isolation: some in one area prefer food one ground and others want food on trees
Behavioural isolation: diff behavioural patterns attract diff partners
Temporal isolation: diff timing of activity (night or day)
Mechanical isolation: some too big or too small to mate
Gametic isolation: zygotes don’t form
What are postzygotic barriers, give examples
Prevent zygote development or reproduction to stop hybrids from gene flow
Reduced hybrid viability: not healthy hybrid, born with defects
Reduced hybrid fertility: may not be able to make babies due to chromosomal differences
Hybrid breakdown: less fertility in f2 hybrids
What are the three possible outcomes of continued contact with two populations
They hybridize readily
They do not hybridize at all (prezygotic barriers)
They do hybrize but the offspring has reduced fitness (postzygotic barriers)
What are the two modes of speciation
Allopatric speciation
Sympatric speciation
(Spontaneous speciation also occurs but is rare)
What is allopatric speciation
Physical barrier divide geographic range (this is called vicraiance event) or population splits by moving to new area (dispersal)
Stops gene flow because population is separate, populations start evolving independently if they can’t breed with each other
Over time different allele become fixed due to mutation, drift, selection
In allopatric speciation, what happens if the barrier separating them is removed. Why?
They may remain separate because they are no longer interbreed because of pre and post zygotic mechanisms
What is peripatric speciation
Small peripheral part of ancestral population separates, over time most of the change occurs in the small population
What is sympatric speciation
No geographic barrier to gene flow, but morphological differences cause them to separate
So then mating between both extremes are discourage or disadvantageous
Caused by disruptive selection where both extreme are present
What is autopolyploidization (spontaneous speciation)
This is when meiosis fail and instead of haploid, the gametes are diploid
If this 2n gamete is fertilized with other 2n (selfing) you get an autopolyploid.
They can only mate with other autopolyploids (reproductive isolation)
What is alloployploidization
Similar to autopolyploidization, but it involves first the mating between two closely related species
What are species concepts
The framework to figure out how to organize the different clusters of variation in nature
