2: counterintuitive Darwinian logic of NS Flashcards
what are the proximate causes for why humans eat so many sweets and sugary drinks? (4)
- sugar tastes sweet
- memory of pleasure from sweet
- genes shape development of nerve cells allowing for perception of sweetness and pleasure
- sensory input from taste receptors goes to brain cells and positively reinforces sweet sensation
what are the ultimate causes for why humans eat so many sweets and sugary drinks? (3)
- sugar is an energy source
- ancestors depend on sugar rich fruits so inherited the same tastes
- those who liked more sugar left more descendants
what is infanticide in Hanuman langurs?
- live in social groups with 1 large male and several females and young
- new male challenges old male
- new males kill old males pre-weened young
- means female becomes sexually active sooner
- male can then reproduce sooner and increase his lifetime reproductive success
what are the 3 considered hypotheses for infanticide behaviour in langurs and which is correct?
- non-adaptive :social pathology brought on by overcrowding- not likely in large groups
- favoured by NS at group level - rare
- favoured by NS at individual level : benefits males engaging in the behaviour and male can father more offspring when he is alpha -> CORRECT
what is the group selection logic? and an example
group selection suggests an individuals behaviours are adaptations assisting survival of the group
- Buffalos may reduce reproductive rate and practice self restraint to avoid overexploitation of groups food
why is group selection rare?
- individual selection usually stronger and groups will all characteristics needed for group selection are rare
- the advantage at the group level must outweigh the individual
- groups often not well differentiated from each other
within the group and at the individual level what is favoured?
selfish individuals as these reproduce more rapidly than altrutic ones
between groups at the group level when space or resources are limited what is favoured?
more altruistic individuals as they have an advantage by defending the group and resources
give 3 examples of species where Alcock discusses infanticide
lions, giant water bugs, jacanas
in a meerkat infanticide study by Young et al 2006:
a) if no other pregnant females what % dominant female offspring survive
b) how does this compare to if other pregnant females are around?
c) when are dominant female litters less likely to survive?
d) when are subordinate female litters less likely to survive?
a) almost 100%
b) 55%
c) when subordinate females are pregnant
d) if another female is pregnant, dominant or other subordinates
why may meerkats kill other offspring?
so the other young cant compete with their unborn offspring for resources
- increases pregnant females fitness by increasing that of the potential offsprings
describe self sacrifice in worker honey bees (4)
- leaves barbed spined sting and part of abdomen in skin so dies
- sting has complex adaptive behaviour including muscles, nerve ganglion, venom sac, alarm pheromone
- stylets drive into flesh and pump in venom
- volatile alarm pheromone guides other workers to intruder
why do worker honey bees show reproductive altruism?
- defence more effective when sacrificed and sting detached
- family protected so worker genes indirectly passed on
- saves reproductive investment
what is the sex change example in Anthias fish? (3)
- F change into M when large dominant M dies so opening in population
- increases individual fitness (better to be dominant male)
- maximises lifetime reproductive success
in the garden orb weaving spider what is the difference in males and females? (5)
- M often smaller
- F highly predatory
- waits near web until female matures
- M plucks strands of web to indicate he’s not food
- sometimes still eaten
how does the male crab spider behave?
ties down female using his web so can mate with her
why may spiders offer nuptial gifts?
female distracted by eating as male mates with her
why are black widows genus names Latrodectus?
latro-servant
dektes- biter
what is the scientific name for the black widow sister species, Latrodectus hasselti?
latrodectus hasselti
give 6 points about the redback spider
- australia
- F larger 450mg compared to 5mg
- F more long lived at a few years compared to 2-4 months
- M mature at younger age
- many M per F, up to 6 in web
- multiple mating
what do M redback spiders do during copulation?
- purposely puts himself in F jaws
- inserts sperm organ into reproductive tract
- flips over into her jaws
- she can consume him while sperm transfer takes place
what does the benefit to the M redback spider depend on?
if are the 1st or 2nd male to mate with the female
what is the effect of cannibalism on the first males paternity in redback spiders?
- if cannibalized females reject 67% second males
- if not will reject 4%
- less likely to remate if cannibalises her first male
- this increases males chances of paternity
what is the effect of cannibalism on the second males paternity in redback spiders?
- 2nd male will gain more offspring if he copulates for longer
- males not cannibalised mate for 11s so 45% available
paternity - cannibalised males mate for 25s and have 95% paternity
what is the male bean weevil penis/aedeagus like
tip covered in hard spines that damage females during copulation
what were the main findings about bean weevils in the siva-jothy et al study? (7)
- spines penetrate lining of female reproductive tract
- more damage to a female that has previously mated so she avoids mating again
- females can dislodge males quicker if she kicks
- damage to female does not reduce fecundity
- damage does reduce female lifespan if she mates more than once
- male winning battle of sexes as no fitness cost to him but are to females
- but evolutionary arms race
when may counterintuitive behaviour prove beneficial?
when looking at behaviour from an evolutionary perspective
what is an adaptation?
a characteristic that enhances survival or reproduction of organisms
what is NS?
differential survival/reproduction of classes that differ in one or more characteristic
what is evolution?
any change in gene frequencies
