Ch. 10: Social Behavior Flashcards
social behavior
interactions w/ members of one’s own species, including mates, offspring, other relatives, and unrelated individuals
benefits of living in groups
survival (dilution effect), feeding (clustered around resources, hunting in packs), mating (availability of mates), 1 can warn others of danger
costs of living in groups
predation (large groups are easy to be spotted by predators), competition, disease (spread quickly is close groups)
lek
location of an animal aggregation to put on a display to attract the opposite sex
dilution effect
reduced, or diluted, probability of predation to a 1 animal when its in a group
territory
any area defended by 1+ individuals against the intrusion of others
- defending high quality territory ensures good resources
dominance hierarchy
social ranking among individuals in a group, typically determined through fighting or other contests of strength of skill
linear dominance hierarchy
1st ranked member dominates all other members, 2nd ranked dominates all but 1st ranked, and so on…
donor
individual who directs a behavior toward another individual as part of a social interaction
recipient
individual who receives the behavior of a donor in a social interaction
4 types of social behavior:
cooperation, selfishness, spitefulness, altruism
cooperation
donor and recipient both experience increased fitness from interaction (+/+)
selfishness
donor experiences increased fitness and recipient experiences decreased fitness (+ donor/ - recipient)
spitefulness
interaction reduces the fitness of both donor and recipient (-/-)
altruism
increases fitness of recipient and decreases fitness of donor (- donor, + recipient)
direct fitness
fitness an individual gains by passing on copies of its genes to its offspring
indirect fitness
fitness an individual gains by helping relatives pass on copies of their genes
direct selection
selection favors direct fitness
indirect selection (kin selection)
selection favors indirect fitness
coefficient of relatedness
numerical probability of an individual and its relatives carrying copies of the same genes from a recent common ancestor
- B x r > C
B x r > C variables:
- B = benefit to the recipient
- r = recipients coefficient of relatedness to the donor
- C = direct fitness cost to the donor
for altruism to evolve, cost-benefit ratio must be…
< coefficient of relatedness b/w donor and recipient
eusocial (“truly” social) species 4 characteristics:
- several adults living together in group
- overlapping generations of parents and offspring living together in same group
- cooperation in nest building and brood care
- reproductive dominance by 1 or few individuals, and presence of sterile individuals
caste
individuals w/in social group sharing specialized behavior
haplodiploid
sex-determination system in which 1 sex is haploid and other is diploid
queen
dominant egg-laying female in eusocial insect societies
dilution effect
reduced/diluted probability of predation to a single animal when its in a group
- strength in numbers
- more individuals watching, increases individuals time for feeding (less time individually watching)
social behaviors ___, ____, and ___ , and thus are subject to ___.
- have a genetic basis, instinctual basis (innate), and learned behaviors
- subject to natural selection
selection has favored ___ and ____
cohesive groups and constrained antagonism (hierarchical order from competition)
trade-offs in group food gathering
larger groups are better at locating food, but food must be shared among all members
territories can be… (2):
- transient territory
- relatively permanent territory
home range is
a much larger area than a territory; area is used but NOT entirely defended
- may defended center of home range
- range of 1 group (1 species in 1 area)
egalitarian ranking
linear ranking system (highest (alpha) –> lowest)
- ex: chickens
- once hierarchy established; ranked dominant and submissive
despotic social order
1 alpha, everyone else equally less than alpha
benefits of being a dominant individual
reproductive success, foraging success
costs of being a dominant individual
higher metabolic rates, higher levels of stress hormones, danger of being killed
benefits of being a subordinate individual
lower risk of injury from fighting, avoid stress, protection by dominant leader
costs of being a subordinate individual
subject to leader, reduced access to food, reduced access to shelter/reproduction
% normal relations b/w family members
50%
what situation would create 75% relatedness b/w family members?
only if there are “sister-wives”
- husband marries wife, wife dies, husband re-marries her sister, their child has 75% relatedness to siblings
inclusive fitness
direct and indirect fitness
2 known animals that are eusocial (other than insects):
- nakedmole rats
- damaraland mole rat
Primary helpers
sons of parents that feed and protect chicks
Secondary helpers
unrelated males that help to feed and protect chicks
Delayers
unrelated and do not help and wait until the second year to reproduce
- after 2 years, delayers have reduced inclusive fitness relative to secondary helpers
naked mole rats…
- only mammal w/o pain receptors on skin
- no cancer
inclusive fitness =
(indirect fitness)*(direct fitness)
