Lecture 16 & 17: Hammond Flashcards
Why do animals behave as they do?
Proximate reason- HOW- Mechanism
Ultimate reasons- WHY- Evolution
Links to tinbergens 4 questions
What are tinbergens four questions?
Proximate: Causation, Development and Ontogeny
Ultimate: advantage and function, history and phylogeny
How do you scientifically study animal behaviour
How do they do it? –> How would you find out? –> Hypothesise –> experiment.
Why do birds throw eggs out of their nest –> could attract predators? –> birds with removed egg shells suffer less predation –> experiment –> true or false
Repeat
Define an adaptation:
A characterisitc that improves the chances of an organism transmitting its genes to the next generation.
Can an adapted characteristic can be behavioural?
YES- e.g. egg shell removal –> increased offspring survival –> increased frequency of trait
How does natural selection produce adaptation.
Start with variation within a species –> some variation is heritable –> competition between individuals –> some varying heritable traits are better adapted to the environment –> these variants leave more offspring –> increased frequency.
What can vary in an organism to produce varying success?
Variation in alleles, variation in expression levels
–> variation in development and function
Why is selection not very strong on a group?
One ‘selfish’ mutant would destroy order in a group that was behaving in a ‘good of the group’ way –> increased frequency of selfishness
What is the strongest unit of selection?
Individuals- organisms survival vehicles for the immortal germ line
What is the trade-off between brood size and individuals?
More offspring = smaller
Fewer offspring = heavier –> increased survival.
What have manipulation experiments in Whythyam Woods shown us about optimal brood size?
Optimum brood size is a higher number than the modal brood size.
Why is optimal brood size greater than modal brood size.
Hypothesis 1: increased brood size –> decreased adult survival.
Hypothesis 2: Manipulation neglects cost of egg development.
What determines the optimal brood size.
Largest positive difference between benefit and cost.
Insert diagram
What has manipulating the numbers of eggs in a brood showed us- what was done?
Either:
- Add 2 chicks to the brood (free chicks)
- Add 2 eggs (free eggs)
- Remove 4 eggs (causes bird to lay 2) and add 4 back (full costs)
What has adding 2 chicks in different ways showed us?
Insert diagram
Hypothesis 1 disproved, support for Hypothesis 2 however female fitness decreases with increased cost.
What determines optimal brood size?
Changing the brood size experiments
Individual interests
The perrcentage of young fledged is always highest when the experiment brood size = inital clutch size
Number of eggs proportional to territory.
What causes changes in the laying dates of eggs?
Increasing warmth has lead to earlier laid eggs
Is the difference in egg laying time due to individual plasticity of genetics?
Insert diagram
Individuals are plastic depending on temperature
Is the link between laying dates and warmth causative or just a correlation?
Due to food supply (caterpillars) are emerging earlier.
Earlier laid eggs have a greater food supply
How is the changes in egg laying dates an example of adaptation?
Plasticity is heritable –> plasticity genes are passed onto the next generation (in higher frequency if proportionally more survive).
What produces the final phenotype?
Phenotype = Genes + Environment
- If environment is constant then variation must be due to genetics.
What is the difference between baboons?
Papio h. hamadrya- herd females with one male units which then are further organised into clans –> bands –> troops MALE phylopatry
Papio h. Anubis - no herding, no organisation, FEMALE phylopatry
How / why can behaviour be selected for?
Due to heritable genetic component
- Dogs (herding, retrieval)
Does the ability to learn have a genetic basis?
Blow flies selected for depending on speed of associating proboscis extension reflex with sucrose reward.
- Fast flies mated together, stupid flies mated together
- -> extreme populations
What link is there between gene number and response time?
Simpler the trait (fewer genes) –> faster fixation
However prenatal, nutritional and experimental variation changes this.
How does drosophilia sitter and rover populations change depending on density?
Rover is dominant 70:30 to sitter
Rover is best in high density groups and sitters in low.
–> sitters can be transgenically modified with over-expressed cGMP dependent protein kinase –> rover like phenotype.
What is the differences in mating behaviour between different vole species?
Prairie voles - monogamous males Montane voles - promiscuous males Differences in promoter micro-satellites --> PV lots, MVs few Insert diagram
What happens if you aritifically select for long and short micro-satellites.
Causes behavioural differences.
- Insert diagram
Longer micro-satellites –> more social
–> no pattern across phylogeny
Is there any patterns with micro-satellites across the phylogeny?
No even though there are distinct differences between voles there is no association across the phylogeny, not even in primates
Are identical twins more likely to be similar due to increase genetic similarity (concordance)
Female infedility is heritable:
38% concordance with number of sexual partners, 41% with epidoes of infidelity. Normally 0.3-0.6 heritable
Define heritability
The extent to which individual genetic differences contribute to individual differences in observed behaviour
Describe the debate about genes and human behaviour?
Genes explain 40% of human behaviour- should the ‘best’ behaviour e.g. mating and IQ, be selected for.
Blank slate theory- only our environment affects our behaviour.
Naturalistic fallacy- morals are culturally determined.
