eeb 100 (animal behavior)

1st half of fall quarter

proximate causation

what causes behavior to occur

sensory motor (proximate)

immediate occurrence in behavior thru internal/external stimuli

ex of sensory motor (proximate)

• psychology

• endocrinology (short-term, activational effects of hormones)

• neurobiology (changes/effects of neurotransmitters)

ontogenetics (proximate)

behavior development

ex of ontogenetics

• genetics

• instincts & learning (experience)

  • endocrinology (long-term, organizational effects of hormones)

ultimate causation

what causes behavior to evolve

functional (ultimate)

how adaptive behavior (if so)

ex of functional (ultimate)

• costs & benefits

• fitness (survival, mating success)

phylogenetic (ultimate)

historical pathway that behavior evolved from

ex of phylogenetic (ultimate)

• evolutionary origins, transitions & precursors

• natural selection

proximate mechanisms are the result of …..

ultimate (evolutionary) proceses

functional hypotheses do ….

not imply that animals understand that animals understand the fitness consequences of their actions

cortical magnification

proportional representation of touch receptors in the somatosensory cortex, as determined by touching different body parts while recording neural activity in the cortex

stimulus filtering is ..

• a fundamental and adaptive property of the nervous system

• onstant bombardment of potential stimuli necessitates filtering out irrelevant stimuli

mech of stimulus filtering

• receptors tuned to respond to particular bandwidths of particular stimuli

• interneuron relay receptor signals to ganglia

• ganglia integrate and process inputs

• ganglia send signals to brain or directly to muscles

hormones come from…

endocrine gland secretions

hormones are

chemical messengers

hormones are transported by

blood

hormones are _____ than neurotransmitters

slower-acting

hormones affect …

tissues with hormone receptors throughout the body

ovaries produce

estradiol and progesterone

testes produce

testosterone

modes of hormone action/effects on behavior

• organizational

• activational

  • not a true dichotomy; two modes grade into one another

organizational hormone action

long-term, developmental effects

activational hormone action

short-term, modulatory effects

organizational effects of hormones set the stage for…

later activational effects

chromosomal sex determination

• females (XX)

• males (XY)

gene on y chromosome codes for protein that causes …

testes instead of ovaries

what mode of hormone action is this?

gonadal hormones trigger sex differences in body and brain development

organizational

what mode of hormone action is this?

gonadal hormones have sex-specific effects on adult behavior

activational

primary function of gonadal hormones

regulate sexual development and reproductive readiness

activational effects of gonadal hormones vary by 

species

mech of endocrine disrupting chemicals

• mimic or block endogenous hormones

• increase or decrease hormone levels

effects of endocrine disrupting chemicals

• feminization or de-masculinization of males

• masculinization of females

• changes in sexual preferences and mating behavior

• changes in parental car

• sterility

• sex change

genotype

• set of genes possessed by an individual OR

• the alleles possessed by an individual at a specific genetic locus

phenotpe

• all characteristics of an individual other than its genotype OR

• a specific characteristic of an individual other than its genotype

mendelian trait

a phenotype that varies among individuals because of variation at a single genetic locus

polygenic trait

a phenotype that varies among individuals because of variation at more than one genetic locus

is tongue rolling a mendelian trait

no, there is a strong genetic basis

“gene for trait X” is shorthand for…

“variation in the DNA sequence at this locus influences the likelihood of developing trait X”

the development of most traits is influenced by numerous genes and environmental factors. how can we sort out the relative influence of genetic and environmental factors?

quantitative traits, frequency histograms, and variances

equation for quantitative genetics

Vp = Vg + Ve

where V = variance, G = genetic, E = environmental

equation for quantitative heritability

h² = Vg / Vp

where h² = heritability, G = genetic, P = phenotypic

what kind of measure is h²

population measure

when looking at a graph where offspring mean (y variable) is influenced by parental mean (x variable), h² (heritability) is the …

slope 

one solution to common environment problem

cross fostering (ex):

• human twin adoption studies

• nest-swapping experiments in birds

R = h²S

heritability can be used to predict evolutionary response to selection

h² = R/S

heritability can be estimated from response to selection

what does the S in h² = R/S mean

the selection differential S is the change in the trait mean caused by selection within the parental generation

what does the R in h² = R/S mean

the response to selection R is the change in the trait mean between generations

what is instincts

innate behavior - behaviors that do not have to be learned (and which are usually triggered by specific types of stimuli)

what is learning

• process through which experience changes an individual’s behavior

• durable and usually adaptive change in an indivudal’s behavior traceable to a specific experience

• does not include changes in behavior caused by maturational growth processes, fatigue, or sensory adaptation

ex of innate behavior

gull chick pecking red spot on parent’s bill

what is habituation

animal learns not to respond after repeated encounters with a benign (harmless) stimulus

• one of the simplest and most universal forms of learning

• adaptive value: conserves energy, time and attention for more important activities

imprinting

forms of learning that depend on exposure to key stimuli during sensitive developmental period and which affects subsequent responses to those stimuli

filial imprinting

(ex) goslings learn the shape/sight/sound of '‘mom” and follow her

sexual imprinting

(ex) goslings later attempt to mate with someoen similar to “mom”

home stream imprinting

(ex) salmon learn the smell of the stream in which they were born; later home back to the same stream to spawn

social learning

catch-all category for forms of learning in which animals in some sense learn from each other

• observational learning / imitation

• basis of traditions and culture

development of behavior is influenced by 

numerous genes and environmental factors

the proportion of genetic variation in a trait can be inferred from

breeding studies and the response to artificial selection

genetic differences between populations can be inferred from

common garden experiments

what animals are capable of learning can generally be explained in terms of their …

ecology

instincts may be favored over learning when conditions are …

predictable or when there is no opportunity to learn

which behaviors are innate versus learned matters in…

conservation translocation programs

what led darwin to natural selection

• effects of selective breeding → also known as artificial selection

• the “struggle for existence” → based on malthus (1798)

darwin’s crucial insight

any trait that gives the individual bearing it an edge in the struggle to survive and reproduce would be more likely to be transmitted to future generations

evolution by natural selection requires:

• variation among individuals in

• heritable traits

• that affect survival and reproduction

if these conditions hold (generally do), evolution by natural selection is inevitable

fitness

the relative number of gene copies contributed by an individual to the next generation - usually measured in reproductive success (number of offspring) relative to the population average

adaptation (process)

changes caused by natural selection leading to greater fit between a population and its environment across generations

adaptation (trait)

a product of natural selection

individual selection

caused by differential survival and reproduction of individuals

group selection

caused by differential survival and reproduction of groups (colonies, populations, species, etc)

altruistic behavior

one that helps others but reduces the individual’s own fitness (their chances of surviving and reproducing)

can altruistic behaviors evolve “for the good of the species”

altruism can’t evolve just “for the good of the species” at the individual level, but Wynne-Edwards argued that if groups with altruists do better overall than groups without them, then group selection could allow altruism to evolve.

wynne-edwards view about group selection

group selection usually trumps individual selection

william’s view about group selection

• group selection is theoretically possible but usually much weaker than individual selection

• reproductive restraint and other forms of true altruism are illusions

• conclusion: “group level adaptations do not, in fact, exists”

is it altruistic to protect your own offspring

no, altruism occurs when it negatively affects one’s self (cost and benefit)

is selection at the colony level required to explain eusociality

no, selection at the colony level is not strictly required to explain eurosociality

eusociality

highest level of social organization found in animals; defined by:

• cooperative brood care

• reproductive division of labor (queen vs workers)

• overlapping generations within a colony

what is the multilevel selection theory

explains evolution by considering that natural selection operates simultaneously at multiple levels of biological organization, such as genes, individuals, and groups

adaptationist approach

• starts assuming animals are well-adapted to natural environment

• comes up with hypothesis to explain why particular trait has evolved through natural selection

• collects data to tests predictions made by hypothesis

• if data not match predictions, modify hypothesis

adaptive behavior

behavior that increases the fitness of the individual performing it, relative to a nearby alternative

maladaptive behavior

behavior the reduces the fitness of the individual performing it, relative to a nearby alternative

possible reasons for maladaptive behavior

• environmental change and evolutionary time lag

• parasites exploiting or controlling host behavior

• gene flow between populations under different selection regimes

• genetic and developmental constraints

• genetic correlation between sexes

behavior evolves thru the same processes as ….

other organismal traits (morphology, physiology)

natural selection can operate at …

different levels (gene, individual, group, population, etc)

there is no reason to invoke group-level benefits for…

traits that increase for the individual (copulatory suicide)

the behavior of animals in the wild is usually…

adaptive, not withstanding some interesting exceptions

most instances of maladaptive behavior can be explained by…

recent changes in the environment (evolution takes place on a multi-generation time scale)

what is needed for group selection to work

suicidal populations would have to colonize areas where non-suicidal populations went extinct faster than non-suicidal genotypes take over suicidal poulation

why has copulatory suicide evolved in redback spiders

suicidal males fertilize more eggs → genetic standpoint: copulatory suicide appears to be selfish, not altruistic

evolutionary arms race between predators and prey

• prey continually evolving defenses to avoid being eaten

• predators are continually evolving counter defenses

economics of prey defenses

net prey profitability = E/T (energy per unit of time)

• E = energy content per prey item

• T = time required to harvest one prey item

T = S + h

• S = search time

• h = handing time

stages of predation

1. Encounter (within detection distance)

2. Detection (as objects)

3. Identification (as prey)

4. Attack

5. Subjugation (preventing escape)

6. Consumption

what prey defenses are effective at stage 1: Encounter, to increase “search time”

• hiding

• inactivity when predators are active

• flight before detection

what prey defenses are effective at stage 2: Detection, to increase “search time”

• immobility

• crypsis (background matching)

• background preferences

• polymorphism (if predator forms search images)

• background-matching movements

• communication on ‘private wavelengths’

crypsis (background matching)

color patterns:

• resemble sample of visual background (as viewed by predator) are cryptic

• contrast with visual background are conspicuous

  • slight degree of crysis increase detection time

  • usually have both behavioral and morphological components

cryptic prey often come in multiple forms. what maintains variation"?

polymorphism - existence of multiple forms or morphs within a population

• term used if known that variation doesn’t have genetic basis

apostatic selection

• type of negative frequency dependent selection

• occurs whenever predators don’t attack prey morphs in proportion to their availability but instead prey more on more common morphs

• favors polymorphism in prey because rare morphs have survival advantage