BOHA- 10 Flashcards
what are the 2 hypotheses for why the female penis originally evolved in hyenas?
Hypothesis 1 - evolved by selection on having high levels of male sex hormones in the young to
allow killing siblings - ‘penis’ is bi product of sex hormones
Hypothesis 2 - evolved by selection on having high levels of male sex hormones that made females larger as adults and dominant over males - competitive skills are vital in their packs
what are the costs of the female ‘penis’ in hyenas?
they have to copulate through it and give birth through it
how do hyenas communicate they want to copulate with each other?
through displaying their genitals to each other
5 examples of sensory modalities
1) ultra violet vision in blue tits - females prefer to mate with males that have blue head most striking in UV light
2) Ravens vocal calling - they only call when there is more than 2 birds at the carcus - it the intruders that call to bring more ravens to overwhelm the 2 territory birds so everyone can feed
3) Olfactory - insect pheromones
4) Tactile - grooming each other
5) Electric pulses used in fishes for courtship and electronic recognition
what is sensory exploitation?
biasing effect of existing perceptual mechanisms on the origins of new communication signals - easier to tap into an already existing communication signal than starting from scratch - new signals are hard because no-one reacts as they’ve never experienced it before
how can you test the seonsory exploitation idea?
if species respond more to novel signal than to a control it gives evidence for sensory exploitation
describe how a cuckoo chick exploits a reed warbler host?
- bright orange mouth same as reed warbler
- larger than reed warbler
- experiment on cuckoo calls shows that the chicks are exploiting sounds of existing perceptual mechanisms to get more food
describe the idea of honest signalling in red deer
the deer roar to see how equal the fight would be - only physical fight occurs when the roars are equal
wha is the problem with honest signalling?
its costly - have to ensure noone can cheat - honest signals cant be faked
give an example of communication between 2 species including the horse chestnut flower
nectar guides are yellow only while pollen is available and then turn red when no more pollen is available - yellow flowers are only visited by insects - bee benefits by not wasting time on unproductive flowers and plant has advantage of insect coming to pollenate its flowers
what does waist to hip ratio signal in humans?
its a signal of reproductive potential and long term health
- study shows males are more attracted to smaller waist and bigger hips
what are the 2 pieces of information needed to understand the evolution of communication systems?
1) the origins of the signal and the changes taking place in signalers and receivers
2) the causal process causing these changes
what does signal size depend on?
its costs and benefits
what are 2 things which are important in the evolution of signals?
1) cumulative selection
2) sensory exploitation
