Evolution and Sex Flashcards
What is sexual selection?
A mechanism proposed by Darwin in 1871 to explain secondary sexual characteristics
Why was another mechanism needed to explain secondary sexual characteristics?
*They are not easily explained by natural selection
*They can be detrimental to survival
*Only appear at adulthood
How does Natural Selection differ from Sexual Selection
*NS focuses on survival; SS focuses on reproduction
*SS influenced by the social environment
2 mechanisms of Sexual Selection
*intrasexual competition - competition for mates
*Intersexual selection - Mate choice
3 types of intrasexual (M-M) selection
Contests, Scrambles, Endurance rivalry
What is Fisherian runaway selection?
Female preference favors a trait that is also favored by NS
Direct and indirect benefits of female choice
*Direct: Protection, resources, disease avoidance
*Indirect benefits: good genes, inbreeding avoidance, parental care
What are the 2 good genes models
*Handicap model - costly traits signal male strength
*Viability indicator model - Visible traits indicate underlying qualities
Sexually selected traits in primates
*behavioral displays
*Acoustic signals
*Ornaments
*Weapons
*Coloration
*Chemical signals
Why is Sexual Selection difficult to study
*Slow reproduction, long lifespan
* complex relationships
*Male sexual coercion
What is parental investment
Investment by a parent that increases offspring survival at the cost of future reproduction
conflicts arising from parental investment
*parent-offspring conflict
*sibling rivalry
*sexual conflict
What determines sex differences in behavior and morphology
The level of PI, not just being male or female
How does PI relate to mating systems
*Monogamy - Monomorphism
*Polygyny - Dimorphism
What is sexual conflict
When male and female reproductive interests do not align, leading to coercion or manipulation
Why do males commit infanticide
To bring females back into estrus and gain mating opportunities
female counter strategies to infanticide
*Confuse paternity through promiscuous mating
*Extend mating periods to avoid male control
*Cryptic female choice
Levels of competition in males
*complete monopolization
*maximizing copulations
*postcopulatory selection
Example of behavioural display
Stiff-leg in Colobus
Example of ornaments
Vervets and Orangutans
Examples of skin coloration
Macaques, Geladas, Uakari
