The Development of Behavior:. Points All Behaviors have some genetic basis. Brain structure, vocal...
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Transcript of The Development of Behavior:. Points All Behaviors have some genetic basis. Brain structure, vocal...
The Development of Behavior:
Points
All Behaviors have some genetic basis.Brain structure, vocal anatomy, etc. determined by DNA
and genetic program in part.
Ex. You can learn languages, but yawns, laughs, and giggles are genetic.
Focused on specific genetic differences that led to different behavioral phenotypes.
Study of genetic basis of behavior is still very young.
All traits are ultimately determined by (gene X environment) interaction.
Funnel web spiders
Susan Riechert conducted a study in Arizona on the predatory behavior of Agelenopsis aperta (J. Evol. Bio. 2000. 13(3):541-550).
Differed by habitat preferenceStreamside population
Very cautious to leave web when capturing prey.
Desert-grassland populationNot cautious. Would run out and grab prey
quickly.
“Common Garden” Experiment
Raise individuals from different populations in the same environment.
If they are the same at maturity, then the differences between populations is primarily environmental.
If they are still different at maturity, then the differences are genetically determined.
“Common Garden” Spider Experiment
Results
Differences in predatory behavior persist.
Therefore
Differences are primarily genetically influenced.
Why are the spiders like this?
Ultimate causation for behavior
Findings:
Desert grassland has few spider predators compared to a streamside community.
Predation has be a selective factor.
Also, food in the desert is less abundant.
If you don’t catch the prey item, you may not see any other food from quite some time.
Period Gene (single genes)
All higher animals/organisms have a periodHumans are affected by mutations to the
period gene as are fruit flies.Also effects Blackcap warblers.
In their case, it affects migratory behavior.
European/Africa birdMigrates 2-3,000 miles and crosses the Sahara
Desert.
Background
Nocturnal migratory restlessness
Jump in migratory direction
Use an internal compass influenced by solar and star cues.
Destination Varies Across Europe
3.15 Differences in the migratory behavior of two closely related birds
Test Migratory Directionality
Common Garden Experiment
Young from different populations try to migrate in a set direction
Test Migratory Directionality
Cross-Breeding Experiment
Cross breed individuals from 2 different populations
Phenotype of offspring will often say something about the genetics.
Cross breed the following:
German BCWA (orient ) and Hungarian BCWA (orient )
What do you get when you cross a priest, a rabbi, and a …?
Offspring will orient in a novel direction ( ), which is an intermediate phenotype.
Intermediate phenotype hints at this being a multi-gene trait and having co-dominance.
Another Cross Breeding Experiment
Cross bred a migratory European BCWA with a non-migratory African BCWA.
Offspring show intermediate degree of nocturnal restlessness.
Drosophila Larval Activity
Two Activity PatternsRovers – move straight lines, go furtherSitters – turn frequently went they
move, don’t move far as a result.
Cross-Breeding Experiment
Pure rover strain(♂) X Pure sitter strain (♀)
All F1 offspring are rovers
Probably just 1 gene/2 alleles involved, with rover allele being dominate.
R R
r
r
Rr Rr
Rr Rr
sitt
er
rover
All heterozygous Rr
Cross F1 Generation
Cross Rr x Rr to get F2 generation.
Get a 3:1 ratio of rovers to sitters.de Belle & Sokolowski (1987)
Gotta love Mendelian genetics.
R r
R
r
RR Rr
Rr rr
rove
r
rover
Questions
What maintains both alleles in a population?
Or
Why doesn’t one allele go to fixation?
Possibilities
1. Natural selection may not be acting on this locus.
2. Selection may fluctuate over time.Each allele may be selected at different brief
times, but not long enough to wipe out any one allele.
3. Frequency-dependant selection (F-DS).Occurs when the fitness of an allele (or organism
with allele, is related to its frequency in a population.
Becomes less fit as it increases in frequency toward fixation, and fitness is highest when it is relatively rare.
So ,F-DS maintains genetic polymorphism.
More single gene effects
Learning ability of mice in a water maze.A spatial memory task
Some mice can’t learn, and never do better than random.
This learning disability is traced to a single geneFunction of the hippocampus (center of
spatial memory)
Parental Behavior in Mice
fos B geneNeurodevelopment of the hypothalamus
Through inbreeding, can produce mice that are homozygous for mutant allele.
Act as normal mice except for parental behavior – ♀ are poor mothers and have trouble raising offspring.
Did you know? Schizophrenia in humans is another single organizational gene.
3.18 Social amnesia is related to the loss of a single gene
Artificial Selection Experiment
Experimenter determines the evolutionary fate of phenotypes.
Fact – if difference in behavior are genetically determined, then the population’s behavior phenotype should respond to selection, artificial or otherwise.
Back to BCWA again
Artificially select for migratory or non-migratory individuals in population.Select based on migratory restlessness.
After several generations, one population becomes two (one pure migratory and the other mostly non-migratory.
Nest Building in Mice
Observation: Mice differ in tendency to incorporate cotton into nest.
Hypothesis: This difference is genetic.
Use an Artificial Selection Experiment
Results: get a cotton loving population and a cotton “so-so” population.
Call Duration in Crickets
Cricket calls are ♂ trying to attract mates.
All populations show variation in call length (hours/night).
Artificial Selection Experiments have shown this variation to be genetic.
Can breed long callers and short callers.
Ultimate Question
What do females prefer?
Long calling is a show of fitness.
however,
Short callers get hit by predators less.
Demonstrating Genetic Effects
The four ways to show genetic effects are:
Common garden experiments
Cross breeding experiments
Artificial selection experiments
Transformation experiments(Taking a gene from one organism and placing
it in another).
Genetic Differences in Alternative Phenotypes
May be genetically different “morphs” even within the same sex.Some fish have can several types of males: parental,
female mimic, and sneaker. (will revisit later)
Ex: Crooked-mouth cichlid in African rift lakes.
Right and left-sided morphs present.Eat scales off of the
opposite side of fish.
Crooked-mouth cichlids
Exist in a 50/50 equilibrium of right and left jawed morphs.
Morph condition is largely heritable.
Maintained by frequency-dependant selection.
Garter Snakes
Behavior: Proximate Ultimate
California garter snakesInland population eats fish and frogs, and
refuses banana slugs.No slugs in the inland environment.
Costal population eats slugs as well as fish and frogs.
Genetics Survival valuePhysiology
Hmmmm, Slugs
Isolated newly hatched young showed a preference based on population.
3.21 Response of newborn, naive garter snakes to slug cubes
Common Garden Slug, I mean Experiment
All young in the same environment.
Exposed young to odor of slug.
Inland snakes tongue flicked a few times and lost interest, while coastal showed great interest and flicked a lot.
Cross Breeding
What do we think cross breeding of these populations will cause?
An intermediate.
Ultimate Level
Inland population don’t have slugs, but are exposed to leeches.Active selection against leech-like /slug consumption.
Why? Cause leeches will eat a snake from the inside out!There are few leeches in the coastal population, therefore
no active selection against sluggy things.
What does the fact that some inland snakes will eat slugs mean to you about the populations?
Application to humans
Jack and Oscar
Identical twins separated at birth (one raised as Catholic in Nazi Germany and the other on a Caribbean Island (Jewish) but still similar in many ways.
Both have similar tastes and mannerisms.
Genetic relationship with IQ
If size can be genetically based, then the volume of the skull can be used to measure intelligence, right?
Wrong!However, genetics can influence similarity of
intelligence.I.Q. closer between identical twins than
fraternal twins.
Main Points
Hormonal influences on behavior
Interaction between learning and behavioral development – biased learning focus
Interactive theory of behavioral development
Interactive Theory of Development
Phenotypic development (including behavior) is strongly genetically determined but may take several alternate pathways depending on the environment.Gene X Environment interactions
Environment is very broadly defined.Both internal (hormonal) and external
Effects of Hormonal Environment
OrganizationalStructure produced during development
due to hormonal condition
Ex. Neurological structures in male birds
ActivationalBehavior triggered by hormone that turns
on an organizational effect.
Ex. Actual singing in male birds as adults
Testosterone is Both Organizational and Activational in Mammals
Fixed Action Pattern
An instinctual behavioral sequence that tends to go to completion once activated.
In mammals, the presence of high testosterone in males drives copulatory behavior.
Let’s look at the organization of fixed action patterns.
Uterine Environment in Mammalian Litters
Location during development of embryos along uterine wall influences behavior.
♂ flanked by ♀’s will be less “male”
♀ flanked by ♂’s will be more masculine than normal.
This is due to leaking testosterone and estrodial.
Rodent Porn
Effects of Uterine Hormones
Effect of estrodial on embryos
Another Example
Organizational and Activational effects in bird song.
Ex. Male WCSP and testosterone treated female WCSPs.
Cascade of Activational Events
Ringed DovesBreeding behavior/cycleAssume – all organization effects are
properly in place. aka. normal adults.
Note – there are no seasons to dove breeding, they just breed all year long if they can.
Dove Breeding Behavior
Courtship and Wooing
Visual presence of ♀ produces testosterone production in ♂.Activates courtship behavior
Male courtship triggers release of follicle stimulating hormone (FSH).FSH stimulates ovarine growth and egg (follicle)
development.
Ovarian follicles secrete estrogen as they develop.Estrogen is important for synchronizing
reproductive development in ♀.
Nest Building Stage
Begins shortly after courtshipPresence of nest and nest-building in
general, triggers progesterone release
Progesterone is important for incubation behavior.♂ must participate in nest building,
otherwise no progesterone and no egg incubation behavior later
Egg Laying
Steps 1 and 2 are important for the production of lutinizing hormone (LH) by the ♀ pituitary gland
This stimulates egg laying in the ♀.
Incubation
Starts from presence of eggs and incubation itself.
Stimulates prolactin productionCrop milk in dove, milk in mammals
Generally stimulates proper parental behaviorInhibits sexual behaviorInhibits FSH and LH productionMaintains incubation behavior
Feeding Offspring
Requires parental care for survivalProlactin activates proper parental
feeding behavior in ♀ and ♂.Parental behavior declines as prolactin
declines late in the season.As prolactin , then FHS and LH (in
females)As prolactin , T (in males)
Back to step one again
Organizational and Activational “Complications”
Classical definitionEverything in the neural net is fixed in
adults
But…there are many cases of neurogenesis in adults
Entire brain structures can appear and disappear in some species, depending on the environment.
Examples of Neurogenesis in Adults
Neurogenesis in “singing centers” in brains of birdsHappens each spring and goes away each
fall.Saves 15-20% energy use over the year.
Neurogenesis in rat sexual behaviorTestosterone “activation” causes slight
change in neural anatomyCreates machinery to do behavior.
More Examples
Neurogenesis in hippocampusInvolved with function of memory
Grows with increased use and demand
Neurogenesis in sex changes among some fish species.Big ♀ will become ♂ in adulthood if it
would be more fit.
To Forage or Not to Forage, that is the Question
Hormones are very important in the development of behavior of workers with a bee hive.
The average sterile worker honeybee has about 1 month to live.
During this time, she generally starts out cleaning cells and feeding larvae, then moves on to feeding nestmates and packing pollen, and finally spends the last week or so actively foraging.
Development of Worker Bee Behavior by Age
What drives this behavior?
Appears to be based on juvenile hormone.
Young nurse workers have low levels of juvenile hormone, while older foragers have much higher levels.
Increases in juvenile hormone stimulates changes in workers brains, creating “mushroom bodies”.
3.2 Gene activity varies in the brains of nurse bees and foragers
What cause the hormone change?
Not fixed by age of worker.
If you create a colony of workers all the same young age,
they still divide the laborSome individuals stay in the colony longer
than normal
Others start foraging up to 2 weeks sooner.
Environmental Factors
Food availability in the hiveIf you remove food from the
hive, more active to forage.
If more larvae (or larval scents) the workers forage more.
Social encounters with foragersIf older foragers are present,
but not allowed to forage, the young are happy to stay nurses.
The presence of older foragers inhibits youthful foraging.
Are Hormones Connected to Age or Task?
Early foragers have high levels of juvenile hormone, even higher than older foragers.
Thus, within colony environment can dictate hormonal behavior in bees.
Experiences Determine…
Sexual preferences
Habitat selection as adults
Nest site selection in birds
Species determination
Are you my mother?
Kin recognition (recognition of relatives)Early learning of kin set many future social
interactions as adults.
Kin share common alleles.
Simple rule – if raised in the same brood, then kin (siblings).
Evolved Recognition Systems
Understanding beyond familiarityEx. Ground squirrels can discriminate related strangers
from unrelated strangers.
Seem to be able to do this by “phenotypic matching”Compare the stranger to self
Kin Recognition in Mammals
Done through olfactionMajor histocompatability complex of glycoprotiens
(MHC’s)Important for recognizing self from non-self in
immune system.
Form the basis for phenotype matching in kin recognition
By licking and grooming, coat self in a blanket of MHC’s or recognition compounds.
Remember the human stinky t-shirt studyMates are more attracted to genetically
compatible scents.
Early Experience and Brain Development
Ex. Food storage in birds and spatial memory.
Early experience with food storing as a young adult ( > 1 month old) causes a larger, more developed hippocampus in Chickadees.