Lecture 23: Speciation Flashcards
What does the biological species concept state?
Species are groups of actually or potentially interbreeding natural populations, which are reductively isolated from other such groups.
Why can determining if two populations are actually different species be difficult at times?
Because speciation is often gradual.
What is speciation?
The process by which one species split into two species.
True or false. Not all evolutionary changes result in new species.
True.
What is the critical process of the formation of new species?
The segregation of the gene pool of the ancestral species into two separate gene pools.
True or false. Speciation is not facilitated by interruption of gene flow among populations.
False. Species is facilitated by interruption of gene flow on one populations.
What is allopatric (geographic) speciation?
Speciation that result when a population is divided by geographic barrier or when some members of a population cross a barrier and form a new, isolated population.
What is starting to be the most dominant form of speciation?
Allopatric speciation.
A barriers effectiveness I preventing gene flow depends on what?
On the size and mobility of the species in question.
What is sympatric speciation?
A partition of a gene pool that occurs without physical separation.
What is the most common means of sympatric speciation?
Polyploidy
What is polyploidy?
The duplication of whole sets of chromosomes.
What are the two ways of polyploidy can arise?
1) Autopolyploidy
2) Allopolyploidy
What is autopolyploidy?
-chromosome duplication in a single species
-can cure accidentally if two deployed damages combine resulting in a tetraploid individual
-usually sterile except for some tetraploid plants that can self fertilize or meet with another tetraploid
What is allopolyploidy?
-the combining of chromosomes from two different species
-can arise an individual individuals of closely related species interbreed, or hybridize
-usually fertile because each of the chromosomes has a nearly identical part to pair with during meiosis
What happens if hybridization occurs, and hybrids are less fit?
Natural selection will result in reinforcement of mechanisms that will prevent this hybridization in the future
What are the two types of mechanisms that can prevent hybridization?
-Prezygotic isolating mechanisms
-Postzygotic isolating mechanisms
When does the prezygotic isolating mechanism operate?
Before fertilization, it will prevent hybridization from occurring.
-spatial/habitat isolation
-temporal isolation
-mechanical isolation
-gamitic isolation
When does the postzygotic isolating mechanism operate?
After fertilization, and reduce the fitness of hybrid offspring.
What is a hybrid zygote abnormality?
The failure to mature normally, either dying during development or having severe abnormalities
What is low hybrid viability?
Hybrids that survive less well than individuals resulting from meetings within populations
What is hybrid infertility?
Hybrid that me mature normally, but be infertile when you get time to reproduce. Ex: Donkey+Horse=Mule
