Tinbergen’s Four Questions
PROXIMATE: - Causation - Ontogeny ULTIMATE: - Function - Evolution
Function in Science
- questions of function are unusual; imply design/purpose of organism = existence of “designer”
- designer in animal behaviour = SELECTION
Selection
- acts to sift variants of beh; favours those who provide bearer w/greater representation in next gen
- DARWIN (1859); selection for survival = NATURAL SELECTION
- NS process is:
1. Huge individual numbers made.
2. Insufficient resource count; death prior reproduction.
3. Individuals vary attributes.
4. Individuals w/attributes better suited environmentally less likely to die.
5. Survivors represented in next gen.
Natural Selection (Example)
COLOURED BIRDS:
- 1ST GEN: varied bird colours (red/purple/brown/blue)
- PREDATION: predator notices red/purple birds more against environment; more killed off more
- 2ND GEN: blue/brown reproduce more; more of them in pop than red/purple (“rare species”)
- SELECTION: blue/brown increase in numbers; red/purple decrease; possible extinction.
Mate Selection
TWO TYPES:
- PASSIVE: aggressive struggle between same sex side (male) via driving away/killing/fighting rivals; females are passive
- SELECTIVE: performance struggle between same sex side (male) via dancing/charming/exciting possible mates; females in control; select personally agreeable partner
- leads to differing offspring dependant on fecundity (fertility/offspring count) or attractiveness (their previous mates/MATES’ offspring)
Behaviour Function
- to either maximise: LIKELIHOOD OF LONG-TERM SURVIVAL - hiding/escaping predators - increasing consumption - reducing spent energy LIFETIME REPRODUCTIVE OUTPUT - increasing attractiveness/mate access/fecundity/young survival
Dysfunctional Behaviour
- behaviour which doesn’t fit the organism’s assumed survival mould
- (ie. praire dogs/common buzzards & rooks/greater sage grouse)
Behaviour Benefits
- DIRECT benefits affect individual performing behaviour
- INDIRECT benefits affect individual and others (ie. kin), though ultimately for offspring; also seen as SYMBIOSIS between unrelated
BB: Examples
RED-BACKED SPIDERS:
- females eat males; vitamins via cannibalism for offspring
OCTOPI:
- female guards eggs then dies after hatching; ensures maximum young develop
LIONS:
- cooperative hunting enables young to benefit via better nutrition/regular meals; secures pride’s future/validity
SALMON:
- good water = essential for breeding; adults die following exertions to breed in home streams but this gives young best life in start
FUNCTION: Summary
- beh “designed” primarily for breeding/longest survival
- beh may benefit others alongside individual
- beh often a compromise between organism & situation regardless of selection pressures
Epistasis
- phenomenon where 1 gene’s expression/repression depends on the presence of the others around it
- we are products of our past; a gene fitness level which doesn’t fit our last 2 genes doesn’t make any sense
Divergent Evolution
- evolution of different features from a common ancestor; leads to differences between species
- ie. monkey/whale/pig/bird all have arm bones
Convergent Evolution
- evolution of similar features in unrelated species via similar environmental pressures
- ie. hummingbirds in different regions have various beak shapes to fit the flowers in said region
Behaviour Arising Explanation
WHEN:
- parsimonious moment (aka. requiring the least changes)
WHY:
- pre-existing behaviour/pre-existing bias/adaptive co-evolution
BAE: Complicating Factors
- MISSING SPECIES; where does behaviour come from if not the fossil? (ie. where does human speech come from?)
- CHANGED ENVIRONMENT; develops in response to climate change to increase individuals’ long-term fitness (ie. siberian tiger adapted to hotter climates by learning to enjoy/cool off in water)
- CHANGED SELECTION PRESSURES; behaviours in themselves changing selective pressures on new gens (ie. beavers building dams which affect the environment in a way which will only be visible around new gen)
EVOLUTIOM: Summary
- behaviours rarely arise fully formed out of nothing; require development/refinement of previous behaviours exhibited by species/relatives
- CANNOT make individual LESS fit than before
- understanding early relatives/behaviours helps us understand modern behaviours
