Evolution and Speciation Flashcards
What is microevolution?
How species change over times
What is macroevolution?
How new species arise?
What is the biological species concept?
Groups of actually or potentially interbreeding populations which are reproductively isolated from other such groups
What are the limitations of the biological species concept?
Is a higher organism targeted theory - only applies to sexually mating organisms
What is introgression?
A gene can move from the gene pool of one species to the gene pool of another (usually geographically close)
What is the initial event to give rise to a new species?
the generation of barriers to gene flow within a species
What is allopatric speciation?
when a population becomes geographically separated
What is sympatric speciation?
Barriers arise to gene flow without geographical separation
What is parapatric speciation?
When adjacent subpopulations have limited contact
What is the problem with the three main models of speciation?
Although the circumstances might exist now, it is hard to tell which factor was actually the causative agent of speciation
What are the two reproductively isolating mechanism in a population which has genetically diverged?
Pre Zygotic and Post Zygotic isolation
What is the Dobzhansky Muller theory?
That reproductive isolation involves interactions at multiple gene loci
What genetic manipulation can be used to prove the Dobzhansky Muller theory?
The use of x linked chromosomes in drosophila
What is Haldane’s Rule?
Hybrid sterility or inviability effects are greater in the heterozygotic sex
How does a series of inversion in a balancer chromosome prevent recombinants?
The series of inversions prevent synapsis of adjacent chromosomes.
If crossovers were to occur, the recombinants would produce aneuploid gametes which are inviable (from acentric and dicentric chromosomes)
How can you identify if progeny contain the balancer chromosome in a screen?
From the dominant visible marker allele
How can you ensure a member of the population does not contain two balancer chromosomes?
They carry a recessive lethal mutation
What is the mathematical theory behind snowball speciation
Quadratic increases of new allele interactions between species
How is chromosomal rearrangement different to balancer chromosomes?
It is a naturally occurring phenomenon unlike balancer chromosomes which are genetically engineered
Where are you likely to find chromosome rearrangements?
In closely related species which are growing in different populations
What is the difference between intrinsic and extrinsic hybrid sterility?
Intrinsic sterility does not rely on environmental factors whereas extrinsic does
What specific category of reproductive isolation does pollination by different insects fall into?
Ecological prezygotic isolation
Why might selection favour prezygotic isolation to postzygotic isolation? (assuming no geographical barriers exist)
It would save ‘cost’ for the species to have prezygotic mechanisms in place = REINFORCEMENT
What is a heterogenous habitat?
A habitat which is not geographically separated but patches of the habitat offer different selective pressures
What is an example of an organism that underwent sympatric speciation (presumed)
The American hawfly
What is the idea of group selection in sexual mating?
The idea of viewing the benefit of the potential mate on the whole group rather than the individual
What is runaway sexual selection theory?
That female choice of mate drives the evolution of a particular phenotype past the point at which it is increasing their (and potential offspring) chance of survival
What is Handicap theory?
Suggests that a particular phenotype can demonstrate a large obvious handicap to an individual - and their survival to adulthood must mean that they have otherwise perfect genotypes
