BIO152H5 Lecture Notes - Lecture 18: Inclusive Fitness

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18 Apr 2012
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Lecture 18 - Sexual Selection and Male Competition
November 17, 2011
Behaviour (cont'd)
Natural Selection and Altruism
- individuals that help close relatives can improve their inclusive fitness
Reciprocal Altruism
- exchange of fitness benefits that are separated in time
Natural Selection and Behaviour
- evolution by natural selection: variation in a trait, variation in fitnes for the trait, genetic basis
for the trait
- evolution of behaviour: behaviours have great variation, diff behaviours have diff fitness,
behaviours have a genetic basis
Sexual Selection and Male Competition
Sexual Selection
- choosing a mate is not random
"...depends on the advantage which certain individuals have over other individuals of the same
sex and species in exclusive relation to reproduction."
Sexual Dimorphism: Armaments
- used for protection frm predators and also for sexual selection
Do females respond? Why?
Exaggerated Traits
- are costly (require a lot of energy)
Is there a benefit?
- enhances mating success, which determines fitness
- if mating success outweighs negatives of predation, still positive for fitness and beneficial.
Origin of Sexual Differences
Assymetry of Sex (unequal-sized gametes)
EGG: resource rich, few, large
SPERM: inexpensive, small, many
The Difference B/w the Sexes
- competition among males for mates
- Choosing among females for mates
Intra-Sexual Selection should favour:
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