Speciation - Ch. 14 Flashcards
What’s the difference between microevolution and macroevolution?
Microevolution- adaptation of populations
Macroevolution- multiplication of species, generating biological diversity
What is speciation?
the divergence of 1 species into 2 or more; the origin of new species
What does the biological species concept state, and what are it’s problems?
Populations/organisms belong to the same species if they can: 1. interbreed (mate) and 2. produce fertile offspring in a natural setting.
Problems: Extinct species, asexual species, remote populations
Solutions/other ways to define species: Observable + measurable traits, ecological niches (role in environment), genetic similarities (DNA)
How can populations become different species?
Reproductive barriers/Reproduction Isolation prevents individuals of closely related species from interbreeding.
What are the prezygotic barriers? (Prezygotic barriers are barriers that prevent mating or fertilization between species)
The prezygotic barriers are:
- Temporal Isolation- mating/fertilization occurs at different seasons or times of day
- Habitat Isolation- populations live in different habitats and do not meet
- Behavioral Isolation- little to no sexual attraction exists between populations; change in behavior reproductively isolates them
- Mechanical Isolation- structural/morphological differences prevent fertilization
- Gametic Isolation- female and male gametes fail to unite in fertilization; they are incompatible
What are the postzygotic barriers? (Postzygotic barriers are barriers that operate if interspecies mating actually occurs and results in HYBRID zygotes)
- Reduced Hybrid Viability- hybrids fail to develop or reach sexual maturity
- Reduced Hybrid Fertility- hybrids fail to produce functional gametes
- Hybrid Breakdown- hybrids are sterile
What are the 2 mechanisms of speciation?
- Allopatric- geographic barrier physically separates populations; gene flow is blocked
- Sympatric- takes place within habitat or parent species; reproductive barrier forms within a subset of population
What’s a polyploid?
Accidents during cell division results in an extra set of chromosomes (polyploid).