Lecture 11 Flashcards
The impact of gene flow on the gene pool depends upon what?
Level of migration, movement, or hybridisation (how often)
Differences in allele frequencies b/w populations
What’s the purpose of gene glow?
Introducing new genetic variation
Reintroducing existing genetic variation
Gene flow tends to:
Homogenize more connected populations
Lack of gene flow promotes interpopulation differentiation
What’s the difference b/w migration & movement?
Migration – between distinct population (less connected)
Movement - between sub-population (more connected)
For gene flow to occur, individuals must be able to . . .
Disperse, interbreed, and produce viable offspring
Gene flow has a large impact on the gene pool of a population when:
The allele frequencies in residents (p) and migrants (x) differ
Migration rate (m) is high
Define speciation.
The evolutionary process by which new species arise through reproductive isolation. It causes one evolutionary lineage to split into 2 or more lineages.
What are some reproductive barriers that prevent gene flow and enable speciation?
Premating isolation → geographical isolation + behavioural isolation (e.g. courtship calling) → allopatric speciation
Selection for different mating signals creates reproductive isolation in the same sympatric population
Pre-zygotic isolation → mating time differences (spawning times e.g.) and ecological differences (e.g. flower shapes - attract different pollinators)
Natural selection has enabled plants and pollinators to co-evolve
Post-zygotic isolation → fertilized egg / offspring unviable
Prevents a hybrid zygote from successfully developing and reproducing themselves
What are the agents of change that cause genetic divergence b/w population in geographic isolation?
Mutation, selection, and genetic drift → chromosomal / DNA differences; change phenotype / behaviour, reproductive isolation
Distinguish between allopatric speciation and sympatric speciation.
Allopatric – speciation in different geographic locations
Sympatric – speciation in the same location
What is adaptive introgression?
Inheritance of beneficial variation from related species that accelerate adaptation to, and survival in new environment
What is hybridization?
the process of producing offspring by mating two parents from different varieties or species - can introduce beneficial traits from one species into another (adaptive introgression)
The species boundary can be semi-permeable and hybrid offspring are not always fertile
DNA fossil evidence show humans, Neanderthals, and Denisovans represent. . .
Separate, parallel lineages descended from a common ancestor
Molecular studies indicate that modern humans interbred with Neanderthals and Denisovans
What is incomplete linear assorting?
When the genetic signals in DNA don’t match what we expect to see in a species tree
