Ch. 16: Speciation Flashcards
What is a species?
- all the organisms that live together in a particular area
- a group of similar organisms that cannot interbreed
- a group of similar organisms that can interbreed
- an adult organism and all of its offspring
- a group of similar organisms that live in the same area
gene flow is required to maintain a species. disruption of gene flow leads to speciation.
What are factors that influence speciation rates?
- ecological specialization i.e. diets
- population bottlenecks
- type of pollination (animal vs wind)
- environmental changes
- sexual selection
Explain the Dobzhansky-Muller model.
- a population is subdivided, then the two groups evolve independently
- in each lineage, new allelse become fixed at different loci. The new alleles at the two loci are incompatible with one another.
- genetic incompatibility between the two isolated populations will develop over time
What is allopatric speciation?
When populations are separated by a physical or geographic barrier. Barriers can form when continents drift, sea levels rise and fall, glaciers advance and retreat, or climates change. The populations evolve through mutation, genetic drift, and adaptation to different environments in the two areas.
What is sympatric speciation?
Speciation without physical isolation. Disruptive selection–individuals with certain genotypes prefer distinct microhabitats where mating takes place.
What is the mechanism of sympatric speciation?
polyploidy: duplication of sets of chromosomes within individuals
What is autoploidy?
chromosome duplication in a single species
What is allopolyploidy?
combining chromosomes of two different species
What is habitat isolation?
when two closely related species evolve preferences for living or mating in different habitats
What is “reinforcement?”
If hybrid offspring survive poorly, more effective prezygotic barriers may evolve, and this is known as reinforcement
What is the hybrid zone?
if reproductive isolation is incomplete, hybrid zones may form where population ranges overlap
How does pollination effect speciation?
speciation rates are higher in animal-pollinated than wind-pollinated plants and are correlated with pollinator specialization
How does sexual selection effect speciation?
sexual selection results in high rates of speciation–especially in birds with polygynous mating systems and high degrees of sexual dimorphism
How does dispersal ability affect speciation?
speciation rates can be faster in species with poor dispersal abilities because they can be separated by narrow barriers
