Ch. 12 Principles of Social Evolution (animal behavior)

eusociality

A complex social structure in which workers sacrifice most or all of their direct reproduction to help rear the queen's offspring. Common in insects such as ants, bees, wasps, and termites.

Altruism

a behavior that benefits others to the detriment of the one performing the behavior (ex: self sacrifice like when colonies of ants are under attack, the workers break open their abdomen spilling a gluey substance onto the intruders, a suicide line of defense )

Wyyene-Edwards (group selection)

proposed that social attributes such as altruisims evolved to benefit groups or species as a whole, rather than the individuals

group selection

the process that occurs when groups differ in their collective attributes and these differences affect the survival chances of the group (species with self-sacrificing individuals are more likely to survive)

George C. Williams

pioneered the idea of gene selection being part of Darwinism--the idea is that animals don't select each other; genes do. And when an animal dies, its gene still lives on and gets passed to future generations (if a group benefit requires an individual to sacrifice itself and reduce its own fitness, then natural selection will trump group selection)

kin selection

type of natural selection that favors the reproductive success of an organism's relatives, even at a cost to the organism's own fitness through self sacrificing behavior

William D. Hamilton (hamilton's rule)

he realized that helping genetically similar individuals other than one's own offspring, survive to reproduce can provide indirect route to the same end

- it doesnt matter which body is carrying certain genes, a trait becomes more common if the allele that promotes the development of that attribute becomes more common, whether through direct descendants or nondescent relatives

coefficient of relatedness (r)

A measure of genetic similarity. The average proportion of genes shared by related individuals.

Hamilton's rule

when C < r x B

C = cost to the altruistic party

r = genetic relatedness

B = fitness benefit to recipient of altuism

Hamilton's rule can be used to explain the evolution of altruistic behaviors AND spiteful behaviors in which an individual damages the fitness of another at cost to itself

direct fitness

producing as many direct descendants as possible will enhance your fitness

indirect fitness

investing in non offspring relatives can also pay off b/c you benefit indirectly - copies of your genes, which your relatives share can be propagated

inclusive fitness

your indirect fitness and direct fitness, added together

superorganisms

group of interacting organisms, where division of labor is highly specialized and where they are unable to survive bythemselves for extended periods of time (ex: amoebae)

evolutionary transitions

intermediate forms have been found that demonstrate how major transitions occurred (formation, maintenance, and transformation of cooperative groups)

- The transition from non eusocial to eusocial insect societies was associated with an increase in behavioral diversity and specialization

haploid

An organism or cell having only one complete set of chromosomes and therefore, only one copy of each gene

diploid

having two sets of chromosomes ans therefore, two copies of genes (one each from a mother and a father)

haplodiploidy

type of sex determination system, in which males are haploid and females are diploid

monogamy hypothesis

lifetime monogamy ensures that siblings are highly related, making obligately sterile workers and ultimately eusociality more likely to evolve