Cycle 7 - Sexy Times Flashcards
Explain how recombination contributes to population genetic variation
- Reproducing sexually generates new multi locus combinations of alleles
- Ex., AB, ab, Ab, aB
- When gametes fuse, we get new and distinct combinations from the parents
Meanings of monoecious, dioecious
Sexually reproducing species may be dioecious (separate sexes) or monoecious (hermaphrodites)
Difference between sequential (protandry, protogyny) and simultaneous monoecy
Sequential monoecy/hermaphrodites: being born one sex and than switching to the other later
- Protandry: male first, switch to female
- Protogyny: female first, switch to male
Simultaneous monoecy: being both sexes at the same time (ex., flowers)
Explain the size-advantage model of sex change
- Plots reproductive success vs. size (increases with age)
- Consider the graph: it is more advantageous to as a male and then at a certain size (the threshold body size) switch to female
Explain the adaptive sex ratio manipulation
Determines which offspring has more to gain from being in good condition.
Example 1: in deer, females in good health tend to produce more males, while females in poor health produce more females because females have less to lose when being in poor condition
Example 2: in birds, attractive males father attractive males, and unattractive males father mostly daughters because females have less to lose from being unattractive
Explain the prevalence of sexual vs asexual reproduction in animals, plants and other forms of life
What are the costs of sexual reproduction?
Most living things are asexual, but in plants and especially animals, most species reproduce sexual
Exclusively asexual species of animals are rare and extinction-prone
- Time and energy consuming, often dangerous (ex., birds’ flashy colours attract predators)
- Cannot pass on all of your genes
- However, it lowers risk of extinction
Explain Muller’s ratchet
States that asexual lineages accumulate harmful mutations
- Rubies in the rubbish: offspring can have fewer harmful mutations than either parent
- Some offspring get lucky and decrease the amount of harmful alleles they inherit so “rubbish” is weeded out
- Asexual selection would show an accumulation of bad alleles
Explain the lottery principle
States that sexual reproduction is maintained because of immediate benefits to individuals that reproduce sexually
- Since the “stock market” (environment) is unpredictable and ever-changing, sexually-reproducting individuals are buying from several stock instead of placing all their money (alleles) into one stock.
Explain the red queen principle
Evolutionary arms race; states that we are running to stay in the same place
- Genotypes that are common in one generation have a low fitness in the next generations because parasites will be most adapted to the most common genotype (Host-parasite coevolution)
- Thus, we conclude that sex is favoured in environments with many parasites
Explain how it is determined which gender experiences selective pressure
- The sex that invests more into offspring (usually females) are more choosy
- Places selective pressure on the other sex (usually males)
“The sex that invests more in the offspring has a lower potential fitness”
Compare intrasexual selection and intersexual selection
Intrasexual selection refers to direct competition of members of the same sex
- Example: male-male competition for a mate
- Favoured traits include large tusks, horns, body size, etc.
Intersexual selection is driven by “female choice”
- Example: a specific breed of bird male spends most of their time constructing beautiful nests for females
- However, these traits intertwine with intrasexual competition, as males often wreck nests of other males
Which sex usually has higher potential fitness?
Which sex has higher average fitness?
- Males, as they have no gestation time and usually have low parental investment
- Additionally, males produce practically an infinite number of gametes
- On average, both sexes have the same general fitness
