Biology 1001A Lecture Notes - Lecture 8: Eusociality, Haplodiploidy, Estrous Cycle
13 Jun 2018
School
Department
Course
Cycle 8
Living in a group
- Social behaviour (interactions animals have with other members of their species) has
profound effects on an individuals reproductive success
Advantages:
- provides a better yield to individuals than working alone
- prey subject to intense predation benefit from group defence
- more pairs of watchful eyes or ears to detect an approaching danger
- multiple lures so that when a predator attacks, it is more difficult to focus on an individual
Disadvantages (costs)
- increased competition for food
- more obvious to predators
- greater risk of inbreeding than those living alone
- Dispersal is a mechanism that can reduce the chances of incestuous matings and
inbreeding
Dominance Hierarchy: when an individual dominates a group, they get priority access to food,
mates, sleeping sites, or other resources.
- In some situations, only dominant individuals (a male and a female) reproduce
- may be absolute, such as when the same individual always has priority access to any
resource
- ex. When a new male takes over a pride, he kills all nursing young, bringing the females into
estrus. This infanticide benefits the male because it increases the chances of his succeeding
at reproducing… increases his fitness
Kin Selection: Individuals are more likely to help close relatives because increasing a close
relatives fitness means that the individual is helping to propagate some of its own alleles
- If benefit to the actors indirect fitness outweighs the cost to the actors direct fitness,
behaviour favoured by kin selection
Altruism: doing something that enhances the situation of another individual
- Reciprocal Altruism: individuals will help nonrelatives if they are likely to return the favour in
the future, both benefit
- would be favoured by natural selection as long as individuals that do not reciprocate
(cheaters) are denied future aid
Eusocial: thousands of genetically related individuals, most of them sterile workers, live and
work together for the reproductive benefit of a single queen and her mate(s). The workers may
even die in defence of their colonies
- Bees: Some pay the ultimate sacrifice when they sting intruders because stinging tears open
the bees abdomen, leaving the stinger and the poison sac behind in the intruders skin and
killing the bee… everything to protect the fertile queen bee
- The high degree of relatedness among workers in some colonies of eusocial insects may
explain their exceptional level of cooperation
- Haplodiploidy: a sex-determination system in which males develop from unfertilized eggs
and are haploid, and females develop from fertilized eggs and are diploid
- workers devote their lives to caring for their siblings (the queens other offspring)
because a few of those siblings, those carrying 75% of the workers alleles, may become
future queens and produce enormous numbers of offspring themselves
find more resources at oneclass.com
find more resources at oneclass.com
Document Summary
Social behaviour (interactions animals have with other members of their species) has profound effects on an individual(cid:1685)s reproductive success. Provides a better yield to individuals than working alone. Prey subject to intense predation benefit from group defence. More pairs of watchful eyes or ears to detect an approaching danger. Multiple lures so that when a predator attacks, it is more difficult to focus on an individual. Greater risk of inbreeding than those living alone. Dispersal is a mechanism that can reduce the chances of incestuous matings and inbreeding. Dominance hierarchy: when an individual dominates a group, they get priority access to food, mates, sleeping sites, or other resources. In some situations, only dominant individuals (a male and a female) reproduce. May be absolute, such as when the same individual always has priority access to any resource. When a new male takes over a pride, he kills all nursing young, bringing the females into estrus.
