Process of social evolution - part 1 Flashcards
what is the fundamental question regarding the evolution of eusociality
why be part of a society instead of going at it alone?
what is the problem regarding the evolution of eusociality
how do the genes for the social action remain in the population?
All social actions can be categorized based on the ____________________ (individual initiating the action) ___________________ (individual engaged by the actor).
- effects on the actor
- and the recipient
define selfishness
Social action in which the actor gains offspring and the recipient loses.
define cooperation
Social action in which actor and recipient both gain offspring
define spite
Social action in which actor and recipient both lose offspring.
define alturism
Social action in which the actor loses offspring, while the recipient gains
define natural selection
Change in the frequency of genes in a population through differential survival and reproduction of individuals because of their phenotypes
define inclusive fitness theory
“inclusive” of both the direct and indirect ways in which a gene can persist in a population
The key insight of William Hamilton (1964) was that when _______________ with the recipient of an altruistic act, it provides an _________________________________.
- genes are shared
- indirect path for those genes to persist
define relatedness
The probability that a copy of a gene at a given locus in one individual is present in another individual
Focus is on whether relatedness (r) is ____________________________ than it is ________________________________.
- higher among two individuals
- generally within the population
__________ is the most common reason in nature for organisms to have ____________________ relatedness
- Kinship
- above-average
define clones
Asexual reproduction of full genetic copies, resulting in relatedness of 1 between individuals (r = 1)
Parent-offspring relatedness
in diploid, sexually reproducing species a parent shares half of its genes with an offspring, with no additional shared copies from a randomly selected mate. (r = 0.5)
Siblings relatedness
In diploid, sexually reproducing species, siblings share 50% of the genes from the maternal half of the genome and 50% of the genes from the paternal half, on average (r = 0.5)
relatedness of female siblings in haplodiploid species
Female siblings share 50% of the maternal half of their genes and 100% of the genes from the paternal half, on average (r = 0.75)
relatedness of female-male siblings in haplodiploid species
Male siblings have only half of maternal genome and none of paternal genome (haploid), so sisters share only half of the 50% of the maternal genome with brothers, on average. (r = 0.25)
haplodiploid societies - relatedness of a queen and her workers, daughter queen, and son
all r = 0.5
haplodiploid societies - relatedness of worker and daughter queen
r = 0.75
haplodiploid societies - relatedness of worker and worker’s son
r = 0.5
haplodiploid societies - relatedness of worker and queen’s son
r = 0.25
Relatedness asymmetries and potential problems?
Workers would rather help their son and the daughter queen and not their mother’s son bc they are more related to their own son and the daughter queen
Hamilton’s rule as a simple algebraic expression
m + rn > 0
Hamilton’s rule - explain the m variable
- change in the actors offspring number (positive or negative, depending on the action).
- “Direct” component of fitness
Hamilton’s rule - explain the n variable
change in the recipients offspring number (positive or negative).
Hamilton’s rule - explain the r variable and rn
- relatedness of actor and recipient
- rn is the “indirect” component of fitness.
sign of m and n variables - selfishness
m is always positive, n is always negative
critical r values - selfishness
can evolve at any r value
selfishness - evolution
evolution is very common
sign of m and n variables - cooperation
m and n are always positive
critical r values - cooperation
can evolve at any r value
cooperation - evolution
The evolution of cooperative acts is favored in isolation, but is often disrupted by the evolution of more, powerful selfish acts.
signs of the m and n variables - spite
both m and n are always negative
critical r values - spite
Spite can only evolve when r < 0
spite - evolution
- Evolution of spite is very rare (remains controversial)
- Most apparent cases of spite, when viewed in isolation, are typically related to larger context of direct benefits through selfishness or other beneficial acts
signs of m and n variables - altruism
m always negative, n always positive
general expression of hamilton’s rule - altruism
-m + rn > 0
critical r values - altruism
Altruism can only evolve when r > 0
altruism - evolution
Evolution of an altruistic act favored when benefit to recipient is high and relatedness is positive
Hamilton’s rule for altruistic acts is alternatively expressed as what
m < rn OR c < rb
what category of sociality requires altruism
- semisocial and eusocial
- bc they require altruism, they are favored by increased relatedness
