Speciation Flashcards
If gene flow stops, what happens to isolated populations?
- Allele frequencies can diverge
- Populations begin to evolve independently
- Divergence may occur due to mutation, natural selection, and genetic drift
What is speciation?
When genetic divergence results in two or more distinct species stemming from an ancestral species
What is the Morphological Species Concept?
When a species shares more similar characteristics with each other because of shared evolutionary history
What is the Genetic Species Concept?
When species share more similar DNA because of shared evolutionary history
What is the Biological Species Concept?
A species contains groups of organisms that can interbreed and produce viable offspring and are reproductively isolated from other species
After splitting off from an ancestral population, each new population evolves in what ways?
Develop mutations independently
Each population has different selective environments
Members of the same species are linked by what?
Shared evolutionary history via the ability to exchange genetic information
What are the limitations to the Biological Species Concept?
Hybrids, extinct organisms, and asexually reproducing species
What are the limitations to the Morphological Species Concept?
Variation within species is tremendous
What are the limitations to the Genetic Species Concept?
Variation within species is tremendous
What is another definition for speciation?
The process by which populations attain reproductive isolation
What is reproductive isolation?
Biological barriers that impede members of different species from interbreeding and producing viable, fertile offspring
What are the 2 categories of biological barriers?
Pre-zygotic and post-zygotic barriers
What are pre-zygotic barriers?
Barriers that prevent mating or fertilization if mating does occur
What are post-zygotic barriers?
Barriers that prevent hybrid offspring of two species from developing into viable, fertile adults
What are the 5 pre-zygotic isolating mechanisms?
- Habitat (ecological or spatial) Isolation
- Temporal or Seasonal Isolation
- Behavioral Isolation
- Mechanical Incompatibility
- Gametic Isolation
What is Habitat Isolation?
When habitat preferences lower the probability of mating between individuals associated with different habitats
What is Temporal or Seasonal Isolation?
When species are prevented from interbreeding due to differences in the timing of mating or fertility, such as having different mating seasons
What is Behavioral Isolation?
When mating behavioral differences prevent mating
What are 2 examples of mating behavioral differences?
- Incorrect courtship displays
- Can’t recognize mating signals
What is Mechanical Incompatibility?
When morphological differences, often in genitals, prevent mating
What is Gametic Isolation?
When the sperm does not survive or physically cannot fuse with the egg
What are the 3 post-zygotic isolating mechanisms?
- Reduced hybrid viability
- Hybrid infertility
- Hybrid breakdown