Speciation Flashcards
What is the biological species concept?
When two groups can reproduce together they are of the same species and their offspring can reproduce
What is speciation?
A process by which one species splits into two species.
Segregation of the gene pool of an ancestral species into 2 separate gene pools
What speciation is caused by a geographic barrier?
Allopatric speciation
What factors affect allopatric speciation?
In different environments, populations will evolve differently through natural selection.
Genetic drift and mutation can also be factors
Most dominant form of speciation
What are the factors that determine the efficacity of a barrier?
Size and mobility of the species
What is symmetric speciation?
Partition of gene pool happens without physical seperation
What is polyploidy?
Duplication of whole sets of chromosomes
How does polyploidy arise?
- Autopolyploidy
- Allopolyploidy
What is autopolyploidy?
Chromosome duplication in a single species.
Occurs accidentally if 2 diploid gametes combine resulting in a tetraploid individual
What happens between tetraploid and diploid populations after autopolyploidy?
They separate because their hybrid offspring are triploid and sterile
Tetraploid plants can self-fertilize (or mate with another tetraploid), which results in reproductive isolation
What is allopolyploidy?
The combining of chromosomes from two different species
This happens when individuals of closely related species interbreed, or hybridize
Why are alloploids usually fertile?
Each of the chromosomes has a nearly identical partner to pair with during meiosis
What are prezygotic isolating mechanisms for? What are the types of prezygotic isolating mechanisms?
To prevent hybridization from occurring
- Spatial/Habitat isolation: live in different locations
- Temporal isolation: Mating periods don’t overlap
- Behavioral isolation: individuals of one species may reject or fail to recognize individuals of other species as mating partners
- Mechanical isolation: have differences in size and shape of reproductive organs
- Gametic isolation: sperm of one species may not attach or penetrate the egg of other species
What are postzygotic isolating mechanisms?
- Hybrid zygote abnormality: fail to mature normally, either dying during development or have severe abnormalities
- Low hybrid viability: hybrids may survive less well than individuals resulting from matings within populations
- Hybrid infertility: may mature normally, but be infertile when they attempt to reproduce
