THEME 1 Flashcards
(48 cards)
What does behavioural ecology aim to assess?
the effects of evolutionary and environmental factors on animal behaviour
What is behavioural ecology?
1) The influence of Natural Selection on behaviour.
2) An animals struggles to survive and reproduce by exploiting and competing for resources, avoiding predators, selecting mates and caring for offspring
3) how animal societies reflect both cooperation and conflict among individuals
What are Tinbergen’s 4 whys?
1) Ontogeny (development) - developmental explanations for changes in individuals (e.g. cognition and imprinting)
2) Ultimate (evolutionary) Why a species evolved the adaptions it has
3) Mechanism (causation) - mechanistic explanations for an organisms’ behaviour (hormones, nerves, genes)
4) Phylogeny (evolution) - the history of the evolution of behavioural changes in a species over many generations (e.g. parental care)
Give an examples of Tinbergen’s 4 whys in starlings
Development
Learnt from parents and neighbours
Ultimate
To attract mates for breeding
Causation
Internal and external factors: increasing day length triggers changes in hormonal levels in the body, or the way air flows through the syrinx and sets up membrane vibrations
evolutionary history
Song evolution – simple sounds in primitive birds, complex songs in starlings evolved
Why do female goats have horns?
- Unwanted advances from males
- Protect and kid and food from other females
- Protection from wind animals in the open (forest bovid don’t seem to have them)
Give 3 ways proximity loggers record behaviour and physiology
Proximity loggers
- Broadcast unique ID & ‘listen’ for other Ids
- Frequency and duration of ‘contacts’ logged
- Data download at recapture
Is there evidence for individual selection?
Individual magpies lay the clutch size that produces most you for them: a function of territory quality. Adapting to resources available
How do phenotype and genotype both get effected by natural selection, and how do they relate to one another in terms of passing fitness onto future generations?
It is the phenotypes of individuals that, by interacting with the environment, are subject to natural selection (selection pressures)
But a phenotype lasts one generation; it is not inherited.
It is the individual genes (and not an organism’s whole genome) responsible for particular aspects of the phenotype being passed into the next generations with varying frequency, depending on the result of natural selection
Dawkins:
Individuals are vehicles; genes are replicators
What did Tinbergen study?
Tinbergen is credited with being one of the founders of the field of behavioural ecology
Examines the adaptive significance of behaviour, or how behaviour may increase survival and reproduction.
Give the modern version of Tinbergen’s questions
Motivation – Proximate/immediate causation
Development – in the individual
Function – What problem does it solve?
Evolution – Ultimate causation
Describe how the ground finch on Daphne Major island, show the evolution of behaviour and natural selection?
E.g. Daphne Major island – Galapagos – medium ground finch
Variable beak sizes
Small bills are better at small seeds and big is big seeds
But in 1985 there was a drought – only small seeds were produced
Therefore natural selection for small billed birds
What was found that in just one year there was a sudden change in the populations average beak size
Describe how speciation could occur in finches on Daphne Island
New finch that was bigger and different song ‘named big bird’ suggested come from other island
Hybrid, could potentially mate with the resident birds but didn’t – females weren’t selecting them because not the right song
How do you measure/investigate the fitness consequences of a behaviour? And how do you measure/investigate the ‘function’ of a behaviour?
Behavioural ecologists seldom do this directly – interns of long term fitness – usually investigate at a functional level. You measure the function of behaviour by:
- Comparative studies
- Experimental manipulation
- Modelling
What is Optimization prediction
behaviour maximises fitness
e.g. Gazelle will visit waterhole x times per day
What is the Optimization criterion
maximum net benefit = max(b-c)
Give the benefits and costs of foraging
Foraging (= searching + handling food)
Benefit = energy intake Cost = energy used in finding & handling food items
What are allocation costs and opportunity costs?
allocation costs = energy/time (usable for other things)
opportunity costs = cost of not performing other behaviours
What are Darwin’s 5 points?
Variation: Individuals within a species differ in their morphology, physiology and behaviour
Heritable: some of this variation is heritable and on average, offspring resemble their parents more than other individuals in the population
Competition: number of offspring produced and number of individuals with successful breeding doesn’t match; population number tends to stay the same – due to competition
Adaption: as a result of competition only the fittest breed – best at gaining resources. This ability is passed on, and through NS over generations adaptions occur
Evolutionary change: in the environment changes then other variants would do best, and therefore NS occurs
If natural selection only works genetically how do behaviours evolve? What considerations should you keep in mind?
- Might still be or have been behavioural alternative
- Differences must be of have been heritable
- Some must have given greater reproductive success than others
Considerations:
- The link between molecular genetics and behaviours is complicated
- The link works both ways, behaviour can effect gene expression
- Genes can be shown to influence behaviour, but might not produce it
Give an example of how the same gene can give 2 different responses in 2 different animals
Drosophila vs. Honey Bees
Drosophila:
2 morphs – sitters and rovers
forR: go foraging much further for food and can take advantage of other food patches, thrive on patchy food and high larval density
forS: sit in the same patch, thrive on evenly spaced uniform food resource
Different alleles of one gene determines this. The percentages: 30% S, 70% R, found in Toronto. Morphs are maintained due to competition being highest within morphs
I.e. a sitter does best surrounded by rovers and the other way around
Bees:
The same ‘for’ gene dictates change in job in worker honeybees
Swapping from sorting honey inside the hive (sitting) or finding nectar (roving)
What did V.C Wynne-Edwards suggest about grouping of species?
If a population over exploited a resource they’d go extinct, so adaptions have come about to ensure the group or species controls it rate of consumption
That they control their breeding rate to prevent over population; producing less young or delaying breeding
Describe the example experiment on Great Tits in Oxford that proves is V.C Wynne Edwards wrong
Nest in boxes and lay 1 clutch ion the spring
Adults and young all ringed
Eggs of each breeding pair are counted (most 8-9 a year)
Young are weighed and their survival is recorded
Results
Incubation ability isn’t the factor, as adding eggs they can still look after them
Once hatched it is the feeding that is the problem
Over a certain size they can’t do it well
Chicks will get less food less often and be smaller when they leave the nest, lighter chicks don’t survive as well
Through experiments there was an optimum number of eggs found to maximize young survival (from a selfish individuals point of view)
The most commonly seen clutch size in birds is seen close to the optimum, but slightly lower…. Why? Give 2 hypotheses
- If brood size effects adult survival it is expected that the brood size that would give the adult greatest reproductive output would be lower than the largest one they could produce for just that season
- Great tits if given more eggs can rear them, but we have ignored the egg production and incubation energy. A fairer test would to be somehow manipulate the birds into laying more eggs, rather than giving eggs
Both hypotheses involve measure trade-offs:
• Adult reproduction and adult survival trade off
• Trade-off between investment in egg production and incubation vs. chick care
What is phenotypic plasticity?
The ability of a single genotype to alter its phenotype in response to environmental conditions (adaptability)