Lecture 13. Evolution of Sex and Sexual Selection Flashcards
What were Darwins two worries about natural selection ?
- Altruism
2. Sexual selection
What are the two problems with sex ?
- How could sexual reproduction evolve in the first place
2. How such mal-adaptively showy males could evolve
Does asexual or sexual reproduction get the most genes into the next generation ?
Asexual
Does asexual or sexual species populate a new environment more quickly ?
Asexual - sexual needs a mate
What was John Maynards Smiths idea called ?
The two fold cost of sex
What is the two fold cost of sex ?
Sexual reproduction is less efficient as
- only half the individuals genes are present in each offspring
- males dont produce offspring directly
What are some other negatives to sexual reproduction mentioned by John Maynard Smith ?
- Courtship and mating takes times, energy and is dangerous
- Finding a mate of the right age, species, sexual state can be difficult
- Courtship is showy which attracts predators and takes time
- Letting another individual that close carries danger or parasites and disease as well an injury
What are the advantages of sexual reproduction at an individual level ?
More variation in offspring leads to:
- Sibling competition reduced
- Better protection against predators
What are the advantages of sexual reproduction at a population level ?
- Mullers ratchet
- Hill Robertson Effect
- Sexual species survive longer
What is sexual reproduction at an individual level necessary for ?
Evolution of sex
What is sexual reproduction at a population level necessary for ?
Help with maintenance but not original evolution of sex
Why do we need to consider individual benefits not population ones when explaining the evolution of sex ?
- Evolution depends on selection between individuals
- The first mutant from asexual to sexual had to outcompete the asexuals in the population
- Benefits only obtained by the population wouldn’t spread a new allele for sex at the expense of the asexual alleles
- Its not for the good of the population that traits evolve
Why do aphids switch from being asexual to sexual just before winter ?
Future conditions are uncertain so variable offspring are a good bet
When do asexual produced offspring do well ?
When environment is stable
What does increase variation mean for siblings ?
Reduced competition meaning offspring survive in many different habitats and offspring compete less as fewer in any one patch
What was better protection against parasites also called ?
Red Queen Hypothesis
What is the red queen hypothesis ?
Evolutionary arms race between hosts and parasites which sexual reproduction can help the hosts win
What is the benefit to the individual parent concerning red queen hypothesis ?
Relief from parasites for some offspring, at least briefly
What is Miller’s Ratchet ?
Gradual accumulation of deleterious mutation
What does Mullers Ratchet effect
Asexual reproduction
What is the Hill Robertson effect ?
Getting multiple mutation into one individual is easier in sexuals
What species survive longer ?
Sexual
What are the two types of sexual selection ?
- Intersexual
2. Intrasexual
What is inter sexual selection ?
Female choice
What is intra sexual selection
Male - male competition
What is the result of inter sexual selection ?
Ardent males and reluctant females
What does honest mean ?
Anything difficult for poor quality, sickly males to maintain
What does female choice create ?
A directional selection pressure towards even bigger and more costly displays in males
What are the two theories to explain extreme males ?
- Fishers Run Away Process
2. Zahavis’ Handicap Principle
What is fishers run away process ?
The trait will continue until the detrimental effect is so strong that the extra chance of breeding is not enough to make it up
Why dont females stop preferring extreme males ?
Sexy sons hypothesis
What is Zahavi’s handicap principle ?
Male is displaying uncheatable signal of good genes as he survived despite handicap of excessive tail
What does evolution not produce ?
What is best for the species
What does selection favour ?
Whoever breeds best and this does lead to mal-adaptively extreme results
