Evolution of sex Flashcards
Sex increases genotypic variance by which mechanism?
Meiosis.
Define anisogamy.
The male and female gametes differ.
In anisogamy, what is the female gamete like?
Large, nutrient rich and non-motile.
In anisogamy, what is the male gamete like?
Small, motile and only contributes the genetic material.
Give 3 disadvantages to sexual reproduction.
- It is energy inefficient and reduces growth rate of a lineage
- Males are techinically a ‘waste’ as they cannot produce offspring
- Sex breaks up beneficial genotypes in recombination. This is a problem is a population is in equilibrium.
What does it mean if a population is in equilibrium?
It is well-adapted, the genes are in optimum combinations.
Under what conditions is sexual reproduction advantageous? List 4.
- Optimal genotypes must be uncommon
- The population must be in disequilibrium
- There is directional selection
- Components of an optimal genotype, the alleles, are distributed throughout the population thus there is a need for gamete fusion.
Why is sex a faster mechanism for adaptation than asexual reproduction?
Asexual lineages have to wait for a mutation to occur, whereas recombinants from sex are frequently produced.
Define Muller’s ratchet.
Asexual lineages irreversibly accumulate deleterious mutations as they are not removed by recombination.
Why does drift have an effect on Muller’s ratchet?
Mutation-free lineages can be lost and mutation-riddled ones can prevail.
What effect does sex have on Muller’s ratchet?
It restores mutated genotypes or creates those that are so incredibly unfit that they go extinct.
What are Red Queen Dynamics?
An ‘evolutionary arms race’, e.g. between pathogen and host.