LIFESCI 3C03 Chapter 7: Ecology Selfish Gene Reading Chapter 7

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Published on 8 Mar 2017
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Ecology Selfish Gene Reading Chapter 7
Family Planning
Decision: unconscious strategic move
Child-bearing: bringing a new individual into the world
- Shall I take whatever steps are necessary in order to bring a new individual into the
world?
- Shall I reproduce?
Child-caring: caring for existing individuals
- If this hild’s relatedess to e is suh ad its haes of dyig if I do ot feed it are
such, shall I feed it?
Child-bearing and child-caring can compete with one another if the individual must choose
between caring for an existing child or bearing a new one.
A pure caring strategy cannot be evolutionarily stable because it does not add new members to
the population, and bearer mutants would quickly take over the new generation.
Parental care is an example of kin selection.
- From the point of the selfish gene, there is no difference in caring for a baby brother
and a baby son
People confuse the fact that child-bearing and child-caring are separate entities because they
are generally intertwined with one another in mammal species.
Population size depends on births, deaths, immigrations, and emigrations.
- Population growth depends on when people have children, as well as on how many they
have. Populations grow by a certain proportion each generation, so spacing out
reproduction timing can slow population growth.
Accelerating population growth is an issue.
- The population of Latin America is growing so fast that if it continues at the rate, the
entire region can be filled with humans standing shoulder to shoulder in 500 years
- This o’t happe eause of faie, plague, ar, ad hopefully irth otrol
- Uncontrolled birth rates lead to increased death rates due to starvation.
Wild animal populations do not grow at the astronomical rates of which they are theoretically
capable.
- Populations tend to oscillate
- Wild animals very rarely die of old age. They usually die by starvation, disease, or
predators.
Animals regulate their birth rates in that they have fixed clutch/litter sizes.
- Family planning
Wynne-Edwards: Populations use formal contests over status and territory as a means of
limiting their size slightly below the level at which starvation itself actually takes its toll.
Groups whose individual members restrain their own birth-rates are less likely to go extinct
than rival groups whose individual members reproduce so fast that they endanger the food
supply.
- Leads to a population of restrained breeders.
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