Psych 118 M1

goal of comparative psychobiology

to uncover common and divergent behavioral processes among species (including our own)

Aristotle

came up with laws of associative learning

came up with a classification system of animals (one of the first of its kind) based on their association to humans

Scala Naturae

Aristotle's classification system of animals (one of the first of its kind) based on their association to humans

Descartes

at the time, it was thought rules that applied to other animals didn't apply to humans \-- Descartes (somewhat) disagreed

thought we were that different from other animals and we had simple involuntary responses (reflexes) as well as free will

Led the way for investigation of animal neurophysiology

Reflex

mediates response to a stimulus. Mechanistic view of animal and human behavior (Descartes)

Dualism

humans have involuntary responses and free will (Decartes)

Physiological basis of behavior

Can examine behavior at the physiological level--behavior arises as a function of nervous and endocrine systems which act upon the same organs (as well as the microbiome)

nervous system

neurons process and encode stimulus input and execute response output

endocrine system

secretes hormones into the blood stream to modulate and orchestrate important behaviors

microbiome

Microbes in the gut and other organ systems that modulate physiology and behavior

Charles Darwin

traveled around the world (Galapagos Island, Tahiti, Rio de Janeiro) leading to his theory of natural selection through seeing the world's diversity of form and function

mental continuity between humans and animals (said humans aren't fundamentally different)

adaptive radiation

the diversification of a group of organisms into forms filling different ecological niches

Darwin observed diversity of the Galapagos Islands, as beak structure depended on function (each island had a separate environment)

What were the Hawaiian web-building spiders an example of?

showed convergent evolution of behavior

on each island, there were the same three types of webs

however, the species that built similar webs were not close in descent; rather, the behavior rose independently as each speciation event occurred separately on different islands

an example of how the environment dictates evolution (filling niches)

convergent evolution

Process by which unrelated organisms independently evolve similarities when adapting to similar environments

Biodiversity

global convergence of form

even in completely different parts of the world \-- there are similar, unrelated features filling similar niches

form follows function (convergent evolution - likely faced similar evolutionary pressures)

what niche might humans fill?

a social, gatherer/predators niche (similar to pigs and wolves)

Comparative analysis of behavior

Allows science to use animal models to study human behavior, because many of the mechanisms of behavior are shared among a wide range of species (Darwin)

- psychology studies behavior which is produced by physiological mechanisms that have been selected for by past environments
- so, evolution by natural selection explains the continuity and diversity in behavior among species

uses the comparative method (wherein similar studies are carried out in different species) given many traits seem to operate via shared processes across species

the comparative method

similar studies are carried out in different species

uses similarities and differences in behavioral processes to reveal the origin and evolutionary development of a behavioral process

homology

similarity resulting from common ancestry
- shared between descendants of a common ancestor

most species have homology in circadian clocks, genetic and neurotransmitter mechanisms for exploratory behavior, genes involved in anxiety, cell-molecular mechanisms of learning, etc.

Genes and Behavior

most behavioral phenotypes:
- Involve complex gene-environment interactions
- Are polygenetic
- Are pleiotropic

some (but very few) behavioral traits follow simple Mendelian relationship (ex. hygienic behavior in the honeybee)

polygenetic

multiple genes affecting a given trait

Most traits are the product of the expression of many genes

pleiotropic

one gene that influences many traits

(T/F) most behaviors are a results of polygenetic inheritance, and most of the genes involved in behavior have pleiotropic effects

T (most common for genes to have both polygenetic and pleiotropic)

how did we study gene-behavior relations historically?

Selective breeding experiments using artificial selection

ex. domestication of dogs (humans breeding for desired traits)

how do we study gene-behavior relations now? (gene expression)

measure expression:
- Immediate early gene expression (IEG)
- Genome Wide Association Study (GWAS)
- Single nucleotide polymorphisms (SNPs)

how do we study gene-behavior relations now? (gene manipulation)

directly manipulating genes:
- Gene mutation (transgenic knock in or knock out)
- Insert into neuron or neural population a single gene coding for a protein (e.g. an ion channel) that responds to light (optogenetics) or chemicals in the diet or via injection (chemogenetics)

artificial selection

Breeding a line of plants or animals by selecting individuals to breed based on their desired traits.

- Provides an analogy that led Darwin to the idea of Natural Selection.
- Traditional method for studying genotype-phenotype relationships.

bidirectional selection procedure

1. Measure phenotype in parental population
2. Breed individuals that score high with each other and individuals that score low with each other
3. Establish control line in which individuals are bred randomly
4. Repeat

what example was used to show the selection for discrimination learning?

blowflies trained on a S+/S- discrimination (predictive and nonpredictive cue)

NaCl + sucrose and KCl - and test

Difference Score \= (\# S+ responses) - (\# S- responses).
- Large Difference Score \= Good Discrimination learning.
- Small Difference Score \= Poor Discrimination learning.

breed like with like

what are the limits to artificial selection?

A behavior that responds little to artificial selection may indicate that the phenotype has undergone intense natural selection in the ancestral population (high and low lines may respond to selection differently)
- resistant to one direction of natural selection

Example: bidirectional selection for avoidance of an odor paired with electric shock during 10 generations in the fruit fly, bred like with like scorers
- found that breeding for high selection didn't make them better, suggested the baseline was as close to max as could be already
- found breeding for HS actually decreased (inbreeding depression)

directional dominance

suggests the behavioral trait is already under strong selective pressure

(the baseline is already as close to the best as it can be)

Directional dominance in humans

Evidence for strong selection during human evolution for Height, Education, and 'g' (flexible, general intelligence)

homozygous populations (such as Amish, Jewish) were impacted negatively

heterosis in dogs

crossbred dogs live, on average, 1.5 years longer

(breeding for recessive alleles tends to reduce fitness)

hybrid vigor (heterosis)

an increase in the performance of hybrids over that of purebreds
- in the fruit fly example, inbreeding increased the number of deleterious recessive alleles while crossing the H and L strains led to regression to the original population mean

Georges Romanes

observational scientist (Darwin's intellectual heir) who studied how behavior develops between animals and humans

relied heavily on anecdotes to build his uncritical views on animal intelligence (for instance, attributing complex reasoning to his cat learning how to open a door)

Morgan & Thorndike (criticisms of Ramones)

Morgan: if you can explain something simply, don't make it more complex

Thorndike: say Ramones was unscientific, say there were issues with anecdotes such as only one case observed, conditions are not controlled, do not know history)
- early experimental scientist

Edward Thorndike (operant learning)

Documented stimulus-response (S-R) associative learning

used a puzzlebox (could cats learn to get out of a box doing a series of steps)
- initially, it took a long time; over time, they got better/faster

thought that if a cat performed a response that got them a reward they liked, it would be strengthened
- thought this was how animals learned behaviors

Perspectives on the experimental study of learning

Ebbinghaus: developed a study of learning through nonsense syllables

Pavlov: noticed his dogs would start, over time, salivating when he entered the room (conditioning)

Thorndike: documented stimulus-response (S-R) associative learning

American psychology

1920s - 1950s: Growth of study of animal behavior in psychology.
- Laboratory experiments: skinner boxes, runway mazes
- Few species employed: monkeys, pigeons, & rats.
- Emphasize malleability of behavior.
- Pros: rigorous control.
- Cons: contrived situations (humans don't live in skinner boxes)

European psychology

Ethology - the study of animals in their natural habitat.

Observational: describing animals in their natural environment (can't conclude causation)
- Emphasize fixedness of behavior, e.g. instincts.
- Pros: greater ecological validity (based on natural conditions)
- Cons: lacks rigorous control.

Tinbergen's four "whys"

What causes behavior?
1. Adaptive significance (what is the behavior good for?)
2. Phylogenetic history (How did the behavior evolve?)
3. Neurological and psychological mechanisms (How does the behavior work mechanistically?)
4. Developmental processes (What experiences and genetic makeup cause the animal to behave as it does?)

(adapted from Aristotle's four "causes")

why does the zebra finch sing? (using Tinbergen)

1. adaptive significance (males sing for a releasing stimulus: females)
2. Phylogenetic history (songbirds have independently evolved singing)
3. neural/psychological mechanisms (its neurons tell it to sing)
4. development (need exposure during sensitive period)

zebra finch song development

in songbirds, there are periods of brain plasticity in order for song learning to work
- need experience during certain periods to develop behavior (ex. hearing songs during sensory period)

FoxP2 expression in striatum (Area X) during active song imitation learning at critical periods in finches.
- if knocked out, bird won't learn
- canaries have periods of plasticity every year (and FoxP2 has higher expression)

why does the behavior exist? (using Tinbergen)

ultimate causes:
- phylogenetic history
- adaptive significance

how does the behavior work? (using Tinbergen)

proximate causes:
- mechanism
- development/ontogeny (what needs to happen during development for it to occur)

ontogeny

developmental history within an individual animal

Darwin's puzzle

How did traits get passed on from parents to offspring?

Blended inheritance

the idea that parental traits become mixed and forever changed in the offspring (common idea at the time)

- Couldn't be correct because traits don't blend.
- ex. Blue eyed mother and green eyed father have children with blue or green eyes, not blue-green eyes.

Particulate inheritance

The observation that genes from two parents do not blend together to form a new physical entity in offspring, but instead remain separate or particle-like.

suggested by Darwin (although, he didn't have a known mechanism) suggestion traits are passed down on a one to nothing basis (get a trait or you don't)

Gregor Mendel

discovered relationship between genotype and phenotype (pea experiment)

monogenetic inheritance (genetics due to one gene)

Phenotype

observed trait (morphology, physiology, behavior, etc.)

Phenotype is the product of the ongoing, dynamic coaction of genes (i.e., genotype) and environmental experience

Genotype

genetic information contributing to phenotype

Adaptation

Traits that increase fitness by definition are selected.

Environment selects traits --\> individual possessing the trait is adapted to its ancestors' environment

Evolutionary mismatch example (adaptation in the wrong environment)

you aren't always perfectly adapted to your current situation (ex. currently produced foods hijack our evolved systems of desire for sugar, salt, and fats)

Fitness

Ability to have and support offspring and pass on your genes

Direct fitness

number of offspring an individual has

Indirect fitness

number of offspring an individual's relatives have

(ex. 2 nieces \= 1 daughter)

ex. scrub jay helpers for nesting pairs
- usually related to nesting pair
- observational study found nests with helpers have more offspring (increase fitness by 30-45%
- then, an experiment (to show causation) removed the helpers from nests and found it decreased offspring

another example is the development of homosexuality in humans (evidence found for families in American Samoa with third gender individuals having increases in fitness)

Inclusive fitness

Direct + Indirect fitness \= Inclusive fitness (W. D. Hamilton)

Kin selection

traits that increase inclusive fitness will be selected for

phylogenetics

evolutionary history of species (how have traits evolved over time)

historical perspectives on the classification of life (taxonomists)

Aristotle - scala naturae

Linnaeus - classification based on trait similarity (invented scientific naming)

Linnean Classification

A classification system that breaks down animals into seven levels, each level being a taxon

goes from more broad to less broad based on shared features

(sub- : distinguishes between taxa that are too big)

historical criteria for taxonomic decisions

Morphology (like with like)

Embryology (comparisons at various stages of development)

Contemporary criteria for taxonomic decisions

Behavior (can use to group animals)

Molecular (protein similarity)
- can use a molecular clock (given DNA degrades at a particular rate)

Genetic (e.g., DNA hybridization & sequencing)

morphology matrix

shows which species have which traits in a table format to get an idea of what the phylogenetic relationships may look like (and to construct phylogenetic trees/cladograms from morphological traits)

derived trait

a new trait that differs from the ancestral trait

(evolved longer ago, less derived traits generally)

phylogenetic tree

A family tree that shows the evolutionary relationships thought to exist among groups of organisms

how to know whether a trait is ancestral or not --\> produce a phylogenetic tree
- evolution results in related trees of individuals
- taxonomy is based on similarity

distance and the length of a line are related to time

(T/F) traits shared by all members are often ancestral

T

cladogenesis

the formation of a new group of organisms or higher taxon by evolutionary divergence from an ancestral form

cladogenesis is the result of the evolutionary process

What are the evolutionary mechanisms of similarity?

homology and homoplasy (through convergence)

homoplasy

A similar (analogous) structure or molecular sequence that has evolved independently in two species.
- occurs through convergent evolution (not from a shared ancestor)
- independently-evolved shared trait

types of groupings based on similarity

monophyletic, paraphyletic, and polyphyletic

pick the one that fits the data the best

monophyletic

a group encompassing the most recent common ancestor and all of its descendants

includes all descendants of common ancestor, and only those descendants

paraphyletic

members all come from a common ancestor, but not all descendants of the common ancestor are included

encompasses the most recent common ancestor, but only some descendants

polyphyletic

groups taxa together despite being distantly related

grouping based on some shared trait, but not necessarily related

How do we determine phylogenetic relationships?

Occam's razor; the simplest explanation is the best (parsimony)

cladistics

trying to understand the relationship between different taxa based on traits are shared or not
- plesiomorphies, apomorphies, autapomorphies, synapomorphies. and homoplasies

all of these terms are relative based on context and only valid in the frame of the specific set of species you are trying to analyze

ancestral traits vs derived traits

ancestral traits are those that existed in a ancestor which may or may not be shared by its descendants

derived traits are those that the ancestor does not have, but at least one of the descendants do

Plesiomorphy

ancestral trait not necessarily shared by all of the descendants and usually *does not help you categorize* what taxa an organism belongs in

apomorphy

derived traits (tend to tell us more about patterns of inheritance than derived traits)

Autapomorphy

A derived trait that is unique to a single individual

Synapomorphy

A shared, derived trait in 2+ individuals that is present in their most recent common ancestor but is missing in more distant ancestors
- Useful for inferring evolutionary relationships.

Most helpful traits for determining ancestral relationships?

apomorphies and synapomorphies

Symplesiomorphy

shared ancestral trait

is the most parsimonious relationship always correct?

not necessarily, but it is correct the vast majority of the time
- can add protein/DNA analysis to check

(T/F) just because a trait is shared, does not mean it's an ancestral trait

T

(T/F) all current living species are descended from one common ancestor

T
life likely has a monophyletic origin; diversity increases over time

How does evolution often occur?

Changes in developmental processes

changes in ontogeny --\> changes in phylogeny

What does natural selection act on?

phenotypic variation (not genetic variation)
- at the unit of an organism's life history strategy

life history strategy

An organism's allocation of energy throughout its lifetime among three competing goals: growing, surviving, and reproducing.

How are new phenotypes produced?

mutation and environmental change

mutation

change in base pair amino acids

Generates variability in structural genes

regulatory genes

Genes that are involved in controlling the expression of one or more other genes.

can be modulated by environmental change

Environmental change

change in expression of a trait when development occurs in a different environment.

- Phenotypic plasticity is the result of a developmental process rather than just mutation.

- The same individual might have different phenotypes depending on their ontogenetic environment

ex. Even "identical" (monozygotic) twins have many differences

Phenotypic plasticity

the ability of an organism to change its phenotype in response to changes in the environment.

The development of the trait is affected by the environment of the developing organism such that in Environment A, the trait develops one way, and in Environment B it develops another way

phenotypes that are originally plastic can be selected for and become stable --\> genetic assimilation

Environmental Modulation of Genes during Development (examples)

1. CHRM2 associated with alcohol dependence & antisocial behavior; had an effect on externalizing behavior during adolescence when parents were neglectful but not when attentive.
- Thus, effects of CHRM2 are moderated by parental monitoring

2. prenatal DHA or not interacts with quality of home environment to determine cognition
- high quality home life improved cognitive while low quality decreased cognition WITHOUT DHA
- with DHA, home life didn't matter as much

Baldwin Effect

an organism's ability to learn new behaviors (e.g. to acclimatize to a new stressor) will affect its reproductive success and will therefore have an effect on the genetic makeup of its species through natural selection

described the effect of learned behavior on evolution (phenotype-first theory of evolution - phenotypes are what are selected for)

can lead to genetic assimilation

Genetic assimilation (canalization)

occurs when a phenotype that initially varies in different environments, later becomes genetically encoded via Natural or artificial selection such that it no longer variable across environments

ex. stability can be selected for if a population remains in a constant environment for many generations

phenotypes that are originally plastic can be selected for and become stable

will result in a loss of phenotypic plasticity

Genetic assimilation example

long-shell variants show plasticity (turbulent or calm water)

short-shells develop short shell regardless of environment - the phenotype is canalized

Standard Model vs. Genetic Assimilation

standard model: mutations occur, and if they're beneficial, get selected for (mutate first, adapt later)

genetic assimilation: adapt first, mutate later (if you have a trait that is plastic enough, it can be selected for and stabilized)