Reproductive Behaviour: Parent Offspring Conflict
Pregnancy is a strange occurrence
o Not normal to have two different immune systems
o Also causes weight gain leading to higher chance of being eaten by predators
Natural selection acts on traits that change gene frequency over time
o Over time, genes in a population will change
o If a gene improves the fitness of the individual, it survives to the next
generation
o Fitness is the ability to produce more offspring
o Natural selection is not evolution
Selection acts on the individual
o A gene is not beneficial to an individual but if it passes into the population, it
becomes beneficial
o Selection will favour behaviour that increases an individual’s genetic
representation in the next generation
Therefore, we expect individuals to act selfishly
This may also apply to genes
Altruism- the selfless concern for the wellbeing of others
o If an individual can benefit from having more offspring, it will
o Theory that women go through menopause so they can care more for their
grandchildren
A person is 50% related to each of their parents
o They are also 50% related to their full siblings
Hamilton’s rule
o Describes the best way to pass on genes to the next generation
o r = relatedness coefficient
How related you are to different family members
o b = benefit to recipient
o c = cost to actor
o rb>c
o If r = 0.5, altruism will occur if the benefit to the recipient is more than twice
the cost to the actor
If you were giving food to a sibling, it must benefit them twice as much
as it would benefit yourself
o Benefits can outweigh costs to initiate altruistic behaviour / prenatal care
The ocean sunfish does not look after its eggs because it produces
around 300 million eggs
Changes throughout nature
o Hamilton’s rule can be used to determine when there is a benefit to being
selfish
Pregnancy is a strange occurrence
o Not normal to have two different immune systems
o Also causes weight gain leading to higher chance of being eaten by predators
Natural selection acts on traits that change gene frequency over time
o Over time, genes in a population will change
o If a gene improves the fitness of the individual, it survives to the next
generation
o Fitness is the ability to produce more offspring
o Natural selection is not evolution
Selection acts on the individual
o A gene is not beneficial to an individual but if it passes into the population, it
becomes beneficial
o Selection will favour behaviour that increases an individual’s genetic
representation in the next generation
Therefore, we expect individuals to act selfishly
This may also apply to genes
Altruism- the selfless concern for the wellbeing of others
o If an individual can benefit from having more offspring, it will
o Theory that women go through menopause so they can care more for their
grandchildren
A person is 50% related to each of their parents
o They are also 50% related to their full siblings
Hamilton’s rule
o Describes the best way to pass on genes to the next generation
o r = relatedness coefficient
How related you are to different family members
o b = benefit to recipient
o c = cost to actor
o rb>c
o If r = 0.5, altruism will occur if the benefit to the recipient is more than twice
the cost to the actor
If you were giving food to a sibling, it must benefit them twice as much
as it would benefit yourself
o Benefits can outweigh costs to initiate altruistic behaviour / prenatal care
The ocean sunfish does not look after its eggs because it produces
around 300 million eggs
Changes throughout nature
o Hamilton’s rule can be used to determine when there is a benefit to being
selfish
