L2 Proximate and Ultimate - why birds sing Flashcards
What are proximate causes of behaviour?
How? the immediate causes of the behaviour and the underlying mechanisms.
What are ultimate causes of behaviour?
Why? the reasons for the behaviour. function and adaptive significance
What questions should you ask about bird song?
1 - How did it develop? innate or learnt
2 - What causes the bird to sing? Stimuli and mechanisms involved
3 - What is the adaptive significance of bird song? how does it increase fitness
4 - What is the evolutionary history? Why did it evolve like this
How does birdsong develop?
Song is partly innate - tonal quality - and partly learnt - phrasing.
What are the stimuli and mechanisms for bird song?
Day length (light) provides stimuli that provokes release of GnRH, which cause testes growth, testes release testosterone, testosterone promotes birdsong
How does season affect testes size?
Differential duration light with day length changes in seasons, so less GnRH.
What are the differences in the song centres in the brains of male and female birds and how does it work?
larger RA in males, which is the part of the brain concerned with song, and is connected to the HCV which sends nerve impulses to the syrinx via the nXIIts.
What is the adaptive function of song?
Two hypothesis for function are:
1) Territory defence
2) Mate acquisition
What is the evolutionary history of bird song?
Three types of bird sing, either evolved independently in each species or there was a common ancestor and the ability was lost by others sharing ancestor
Why is it difficult to establish when a behaviour evolved?
Doesn’t fossilise
How do ethologists trace behaviour?
Map behaviour trait onto phylogenetic trees, pioneer was. Lorenz, made the link between phylogeny and behaviour
What would we expect to see if birdsong evolved in a common ancestor?
Song centres in the brain should be similar, however they aren’t
Imagine that a behavioural biologist tells you they are studying the courtship behavior of a spider and using a portable brain scanner to compare the brain activity of courting and non-courting spiders. Which of Tinbergen’s four types of question are they addressing?
Proximate
A proximate factor in animal behaviour is one concerned with:
Underlying mechanisms of behaviour
An ultimate factor in animal behaviour is one concerned with:
The survival value of a particular behaviour
