BIOL 1011 Lecture Notes - Lecture 10: Inclusive Fitness, Florida Scrub Jay, Breeding Pair
Ecology of Behaviour
March 3, 2015
Behavior is a product of natural selection. Those with more appropriate behaviours
are more like likely to pass their genes onto the next generation.
We explain behaviour in terms of its effect on individual fitness
• Benefit: if fitness increases
• Costs: if fitness decreases
Social Behaviour – interactions between two individuals
Types of Interactions:
1. Benefits Actor and Benefits Recipient = cooperative (defense hunting)
2. Benefits Actor and Harms Recipient = selfish (territorial)
3. Harms Actor and Benefits Recipient = altruistic
• For example, alarm calls warns others but increases risk to itself
4. Harms Actor and Harms Recipient = spiteful (wasteful killing)
W.D. Hamilton focused on inclusive fitness (total effect on the number of genes
passed on). They must produce offspring or aid their relatives to produce more
offspring to help send their genes onto future generations.
Kin Selection – selection for an act that enhances the reproductive success of an
individual’s relatives
Hamilton’s Rule: Natural selection favours an act if C<rB
• C – cost to altruist
• B – benefit to recipient
• Relatedness (shared genes)
How to calculate the relatedness (r):
• Count number of shared alleles
o Child has half of parent’s genes
o Child has a quarter of grandparent’s genes
• r=(1/2)n
o n = number of links
• For siblings,
o You share ¼ of genes from the mother
o You share ¼ of genes from the father
o Therefore, r=1/2
find more resources at oneclass.com
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Document Summary
Those with more appropriate behaviours are more like likely to pass their genes onto the next generation. We explain behaviour in terms of its effect on individual fitness: benefit: if fitness increases, costs: if fitness decreases. Hamilton focused on inclusive fitness (total effect on the number of genes passed on). They must produce offspring or aid their relatives to produce more offspring to help send their genes onto future generations. Kin selection selection for an act that enhances the reproductive success of an individual"s relatives. How to calculate the relatedness (r): count number of shared alleles, for siblings, you share of genes from the mother, you share of genes from the father, therefore, r=1/2. If risk of drowning is 0. 8, cost is too high: r=1/2. For pikas, alarm call is more beneficial than costly. Altruism between non-relatives is very rare: an example is a stable social group with (cid:498)tit for tat(cid:499)
