Darwin’s theory
Proposed that sexual selection is a form of natural selection - selection of traits that increases mating success
Why are females picky with mates?
Females have fewer eggs (than males have sperm) - so can’t afford to “waste” any on mating with unworthy males
- also carry young, give birth, lactate etc
Do males have greater reproductive potential than females?
yes, they can father more offspring
why does sexual selection rise?
males compete for females whose eggs are a scarce resource. this leads to males competing more males
Intrasexual selection
direct male to male combat. however, a fight will only occur if both males are a similar size/strength.
Intersexual selection
Females prefer to mate with males who have an exaggerated form of male trait
What impact does the environment have on mate choice?
- sound (vocalisations) can be used to attract mates - need to be loud to hear over noise pollution in city
- sunlight (make peacocks will angle feathers towards sun to be more attractive)
Strategies for mating
- courtship / nuptial gifts
- displays (peacock tails)
- aggressive competition
- sperm competition
Example of courtship feeding / nuptial gifts
Male spiders will bring food to the female to say they want to mate
examples of Courtship displays
- peacocks will show off their feathers
Sperm competition
- competition between sperm from rival males to fertilise egg
- sometimes mate guards female to prevent further mating
- copulatory plugs (stick insects and guinea pigs. plugs prevent mating)
