Altruism – is “self-sacrificing” behavior
Altruism lower’s the helper’s reproductive success while increasing the reproductive success of the individual being helped.
Many insects like ants, termites and bees are sterile and do not reproduce
- So, how can individuals pass on genes if they can’t reproduce?
Coefficient of relatedness = r
• The probability that any two individuals will share a copy of a particular gene
• In a diploid species, any given allele has a 50% chance of segregating into a particular egg or sperm.
Degree of genetic relatedness to “self” in a diploid organism.
Direct Selection: acts on traits that promote success in personal reproduction
Direct Fitness: a measure of personal reproduction (your own offspring that survive and reproduce)
Indirect Selection (Kin Selection): acts on traits that promote success in the reproduction of nondescendant relatives
Indirect Fitness: a measure of the number of relatives that the altruist helps to survive and reproduce
Inclusive Fitness: Direct + Indirect Fitness (A total measure of the genetic success of an individual)
• Hamilton proposed that an altruistic gene will be favored by natural selection when the indirect fitness gained by the altruist is greater than the direct fitness it loses as a result of its self-sacrificing behavior or:
rbB > rcC
• B – the extra number of relatives that exist thanks to the altruist’s actions
• rb – the coefficient of relatedness between the altruist and the extra individuals
• C – the number of offspring not produced by the altruist
• rc – the coefficient of relatedness between parent and offspring