Exam 2 Flashcards
Behavior is a phenotype
Affected by both genes and environment. Differences in behavior between individuals can be traceable to differences in either genes or environment
Development Of behavior
Two developmental categories of behavior:
– Innate: performed without experience/incentive
– Acquired: gained through experience/learned
Twin studies
Behavioral heritability in humans
– Developmental systems (are dependent upon genetic and environmental input) -> neurophysiological systems (including the brain) –> test taking behavior –> IQ score
Drosophila larva
– More clear-cut example of how differences between individuals can be traced to environmental/genetic differences
– Rover versus sitter fruit fly larva behavioral phenotypes. Larva of one doesn’t move much, other does.
– – Differences caused by a single genetic difference. Crossbred sitter male with rover female to try and prove this. F1 almost all rovers. F2 generation had rover 3:1 sitter ratio. Expected Mendelian ratio.
Mouse water behavior experiment
– A single gene mutation in hippocampus affects spatial learning in mice (alpha-calcium-cal modulin kinase)
– – Put them in water filled tank with platform hidden somewhat underwater. Swims randomly until it finds the platform and then must remember where it is later. There is a mutant that can’t remember where platform is regardless of trial numbers or trial manipulation.
Learning involves environmental modification of behavior
– However… What and how an animal learns is constrained by genes
– Example: taste aversion learning in rats. Good at associating particular taste with nausea – with one trial, will avoid it. Good at associating sounds with electrical shocks. These things are learned but constrained by genes.
– Can’t compare taste with shocks. Can’t pair sound with nausea and get them to stop drinking non-flavored water.
– – And wild, I generalists and need to know quickly if they’re eating something fetid. Need to learn quickly what predators sound like
Vampire bat experiment
Vampire bats don’t have much of a dietary range. Insectivorous bats, however, eat a wide variety of insects, many of which could make them sick.
– Experiments with flavored fluid either mixed with saline or with toxin to make them nauseous – either delayed effect, immediate, or asynchronous.
– – No effect on vampire bats – did not seem to associate the variables. It’s like the worst that’s easily avoided fluids that predictably made them nauseous.
Model for behavioral development
Genes x environmental interactions –> development –> anatomy/including microanatomy (–> innate behavior) and physiology (–> acquired behavior)
Each individual’s behavior equals a mix of genes and environment. Between populations, behaviors can be different solely because of genes.
Do genes for behavior exists
Genes for proteins exist.
– The proteins affects neural development (enzymes, etc), sensory reception (stimuli filtering, etc), cellular communication, production of and response to hormones (hormone can’t do job without receptors in right place with right density)
Etc!
How do you test the role of genes in producing behavioral differences
– Knockout experiments, hybridization experiments, hold environmental condition constant, artificial selection
Knockout experiments
Gene of interest deactivated to see how they behave different from control. Tests single-gene effects only.
Example: female mice with defective FosB gene ignore their offspring, which affected female care for offspring. Showed up FosB gene is necessary to produce normal maternal behavior.
Hybridization experiments
Crossbreed to see diff phenotype type outcomes of different behavior parents
– If there are behavioral variants, read them together. Can see you weather predictions about gene effects on behavior are true
– If polygenic, should be able to hybridize extreme forms of phenotype, expect offspring with intermediate levels of phenotype with a frequency curve
– – Flatter bell curve with higher standard deviation, average is intermediate behavior
Example: blackcap migration (polygenic)
– South German birds migrate to Africa via western route. Eastern European birds migrate via eastern route. Canary island birds don’t migrate.
- Zugunruhe (restlessness of captive birds during migratory times. Length of zugunruhe reflect length of migration in nature) exhibited by different populations
– Crossbreeding Canary Island and south German populations resulted in intermediate migratory route with intermediate length of zugunruhe
– Proved offspring inherit migratory distance and direction behavior
This is an example where two populations from the same species were crossed
Control for differences and environmental conditions
Control for environmental variables that might affect behavior. See if they are different.
Example: garter snake diet preferences. Coastal ones eat slugs, inland ones eat frogs/fish – avoid/not interested in slugs
– Captured pregnant females, raised young in captivity. Offered young either slug chunks or slug fluid on a Q-tip.
– – Crystals next still ate more slugs then and then once despite controlling for environmental differences – support that the preference is genetic
– Coastal snakes tongue flicked more often than inland then snakes in response to slug extract
– This can be attributed to differences in receptor density that makes coastal snakes more sensitive to (proximate or developmental causation)
– – ultimate explanation: not as many slugs inland, not as much selective pressure in favor of individuals who eat slugs
Problems with captivity experiments
Appropriate signs stimuli may not be present, lack of motivation, normal maturation process may not take place
Can do field exps instead
– Control for developmental factors.
– Example: cross fostering in pink cockatoos and Galah
– – Naturally cross foster each other’s offspring. Galahs sometimes lag eggs in same nest holes as cockatoos - chased away and cockatoos raise eggs/chicks. Can take parents with different calls and switch eggs on purpose to try and account for differences in calls
– Call types found in both species: begging, alarm, contact
– Cross fostered galah chicks gave galah begging calls, Gala alarm calls, cockatoo contact calls. Indicates contact calls are learned
Artificial selection
Should be able to produce directional selection to change behavior
– Example: house mouse nest building. Can breed extreme phenotypes among themselves. If genetic variation is responsible, should be able to breed for this extreme phenotype ever many generations to increase the average phenotype
Role of environment in producing behavioral differences
Behavioral development can be affected by things like
Internal environment:
– Hormones
– Environment
External environment:
– Pheromones: chemical signal released by an animal that can affect the behavior of another/affect the course of other animals development and behavior
– Social environment
– Experience/learning
Hormones have two classes of effects on behavior
Activation of effects: trigger behaviors by activating neural pathways that are already in place. Usually occur during adulthood. Effects are transient, meaning that behavior only lasts as long as that hormone is present and in sufficient amounts
Organizational effects: organize neural pathways responsible for behavior
Organizational effects
– Organize neural pathways responsible for behavior. Occurred during early development. Effects are permanent (eg, brain wiring)
Examples of organizational effects: rodent sexual behavior
– Genes on Y chromosome cause development of testes -> testes produce testosterone –> testosterone masculinizes the brain –> the neural pathway in brain that results from this produces male sexual behaviors such as mating/courtship
– – Final expression of male behavior affected by hormone exposure in developmental environment
This can be seen in male parental behavior in Mongolian gerbils. Males positioned between females in utero exposed to less testosterone and fail to mount females in estrous:exhibit more parental care (similar to female behavior)
Egg laying/maintenance behavior in crabs
Normally expressed in females only. However, not so when infected with the parasite Sacculina.
The parasite enters crab at midgut, grows and produces rootlike structures until it is intertwined completely with crabs tissues. When ready to reproduce, extends parts of self out of crab so that it looks like an egg sac. Crab thinks it’s an egg sac too and takes care of it until it hatches to new baby parasites, which looks similar to crab larva.
If the parasite infects a male crab, the root nodules of the parasite neuters the males, which inhibits testosterone and causes the female behaviors that were not normally express and causes it to maintain the egg sac.
Diet
– Some foods act as developmental switches.
– Example: caste determination in honeybees. Worker jelly produces worker bees (4% carbohydrates). Royal jelly produces queens (12% carbohydrates).
Both produced by workers’ salivary glands.
Pheromones
Caste determination in termites.
– Worker/soldier substances inhibit development of own caste. Negative feedback loop.
Example: more workers there are, the more worker substance there is inside colony, which shuts down their development so more soldiers are produced and vice versa
Social
Example: development of task performance and honeybees. Age-related changes in behavior mediated by juvenile hormone (organizational effect)
– Youngest worker bees stay at hive to feed larva/clean/etc. Only forage once they are older to limit reproductive risks since foraging is risky – allows them to contribute to colony before foraging and possibly dying
– – When they make transition depends on balance of bees at other stages within the colony. Affected by social environment. If you add older bees, most of them take on roller forager automatically. If you add younger bees, resident bees which are young, but younger than those added, switch to becoming the foragers
– Socially mediated sex change: female wrasses become male when males removed. (Protogyny)
– – Oldest, heaviest female switches sex when dominant male removed. - - Protandry: start male
Socially mediated territorial behavior in cichlids
– Territorial and satellite phenotypes are reversible in males – depends on status
– Effects whole biology of male. Reversible: can go back told phenotype after
- GnRH neurons -> testes growth -> testosterone -> aggression
– Triggered by ownership of territory
What is learning?
– An adaptive change in an individuals behavior traceable to a specific experience in that individuals life
– Requires flexibility, cannot be considered apart from an animals ecology and evolution
– Adaptive significance of learning is based on the ability to cope with environmental variation
