BIO220-FINAL EXAM- UofT-2023 sem2

Both of these influence phenotypes (including behaviours)

1) Genes & 2) Environment

How does natural selection effect behaviour?

Natural selection SHAPES behaviours

Enviromental effects on trait values are

plasticity

Can plasticity be adaptive?

yes, but it isn't always

the influence of _____ and ______ can be visualized with plots of the reactive norm

the influence of genes and environment

natural selection and reaction norm

natural selection shapes the reaction norm

reaction norm

pattern of phenotypes an individual may develop upon exposure to different environments

Two classes of scientific questions

1) How/what (Proximate causes)

2) Why (Ultimate causes)

How/what

What is the causal

relationship between

the organism's genes

and its behaviour?

aka PROXIMATE CAUSES

Why?

Why has this behaviour evolved and how has it changed over evolutionary time?

ultimate causes

Phenotypes reflect both

genetic and environmental effects

phenotype is:

the gene + enviroment + the genexenviroment interaction

Rover‐Sitter Polymorphism

the occurrence of two or more different forms or morphs within a single species.

These different forms can have different physical characteristics, such as coloration or shape, or different behavioral traits, such as mating behaviors or feeding habits.

within population variation in a behaviour:

Rover/Sitter Polymorphism

Rover/Sitter Polymorphism: YEAST

ROVERS: move more than sitters

Rover/Sitter Polymorphism in GENES

example: the foraging for gene (A-rover, vs C-sitter in sequence)

Rover/Sitter phenotypes

Rover is dominant

Cost of being a rover/sitter

expend more energy looking for food/find less food

benefit of being a sitter/rover

find more food/conserve energy

Evolution by natural selection requires

- Variation in a trait

• Genetic basis for the trait

• Variation in fitness for the trait

Can behaviours evolve?

Behaviours have lots of variation

• Behaviours have a genetic basis

• Different behaviours have different fitness

CONCLUSIONS: rover‐sitter

A single major gene (for) underlies the rover/sitter polymorphism•

The rover allele (forR) is dominant to the sitter allele (fors)

• Both larval and adult behaviours are affected by these alleles

• Elements of the environment (e.g., food deprivation) also affect these behaviours

• Homologous genes exist in bees, mice, and humans

R/S: Genotype effect:

being a rover vs sitter

R/S: environment effect

hours of food deprivation

Plasticity can be:

an environmental effect on the phenotype of a single individual

OR

• an environmental effect on the phenotype of genetically‐identical individuals

VISUALIZING the REACTION NORM

reaction norm describes

the effect of some environmental variable on the phenotype of a single genotype

Reaction norm: Z=G + e

LARGE GENETIC EFFECT

small environmental effect

reaction norm: Z = g + E

small genetic effect, LARGE ENVIROMENTAL EFFECT

reaction norm: Z = G + E + GXE

complex gene x environment interaction

Evolution of Reaction Norms: population mean reaction norm

pic in notes

Genetic variation and evolution of reaction norms: DAPHINIA

Daphnia populations with a selective history of predation risk have evolved to avoid habitats with high risk of predation

sexual dimorphism

The phenomenon in which individuals ofdifferent sexes of the same species havedifferent genotypes and/or phenotypes

examples of Sexual dimorphism

- differences in gametes (anisogamy)

- differences in reproductive organs

- other sex-associated phenotypic differences

MALES CHROMOSONES

Genetic male: XY (humans), ZZ (birds)

FEMALE CHROMONES

XX (humans), ZW (birds)

Anisomgamy

unequal sized gametes

gametic males

sperm producers

gametic females

egg producers

sexual dimorphism can be seen in:

- size

- armaments

- ornaments

sexual selection

a subset of natural selection where:

Sexually selected traits function to enhance mating success

FITNESS =

natural selection (survival + reproductive rate)

+

sexual selection (number & quality of mates)

two types of sexual selection

intrasexual selection (competition)

intersexual selection (choosiness)

What determines thestrength of sexual selection?

number and quality of mates

operational sex ratio

the ratio of male to female individuals who are available for reproducing at any given time

What determines the operational sex ratio?

Anything that alters the receptivity of one sex to mating, or their potential for remating, can alter the operational sex ratio

What drives sex differences in potential reproductive rates (PRR)?

EGG- resource rich and large, but few

Sperm: inexpensive, many, small

Parental Investment Theory

- by Robert Trivers

- Each offspring in these species is produced from a

sperm and an egg

- Members of the sex that invest little in off spring will compete among themselves to mate with members of the sex that invest more in offspring

sperm bearers compete against each other to mate with egg bearers

IMPLICATIONS OF Trivers: If the ONLY investment in offspring is gametes, then:

- Fitness limited by access to fertilizable gametes

- Fitness limited by access to resources

IMPLICATIONS OF Trivers- PREDICTIONS:

Competition: between males for mates

Choosing: among males for mates

If males are limited by access to mates,and females aren't (as much)

refer to image

INTRAsexual selection

Competition

- often male-male competition

INTERsexual selection

Choosiness

- often females choosing

Intrasexual selection:competition FORMS:

pre-copulary (# of copulations)

post-copulatory (success of copulations)

Manifestations of competition: pre‐copulatory

- fighting behaviour

- social status

- territoriality

Manifestations of competition: post‐copulatory

- mate guarding

- copulation duration

- sperm removal

- sperm plugs

- anti-aphrodisiacs

Alternative reproductive strategies: how is variation maintained in a population?

- rock-paper-scissors

game in nature

- observed in side-botched lizards

- strategies have a genetic basis

- orange vs blue vs yellow

- vary in frequencies

Side‐Blotched Lizard Strategies- ORANGE

- Aggressor

- defend large territories

- extremely aggressive towards all males

Side‐Blotched Lizard Strategies- BLUE

- guarder

- defends smaller territories

- detect and root out yellow males

Side‐Blotched Lizard Strategies- YELLOW

- sneaker

- sneaks up on orange males

- mimics throat colour and behaviour of receptive females

Side‐Blotched Lizard- ROCK PAPER SCISSOR GAMES

ORANGE: attack and defeat blue (ADB)

Blue: detect and defeat yellow (DDY)

Yellow: female mimicry and fools oranges (FFO)

Side‐Blotched Lizard PREDICTIONS:

If orange is common, yellow will increase

If blue is common, orange will increase

If yellow is common, blue will increase

SIDE botched lizards: RESULTS

negative frequency dependent selection

negative frequency dependent selection

The fitness of a strategy is highest when that

strategy is rare in the population.

DARWINS ornament puzzle

solved by sexual selection

Mate choice

Any trait (behaviour, morphology) of one sex that biases the mating success of the other sex toward the "preferred" type

Mechanisms of choosing

- visual cues (birds, fish, cricket)

- acoustical cues (cricket, birds, frog)

- tactile cues (Sierra doem spiders)

- olfactory cues (mouses, bees, cockroach, moth)

Tail lenght experiment predictions

BEST:

L > N

WORST

S > R

tail lenght experiment RESULTS:

TAIL LENGHT ONLY INFLUENCES FEMALE CHOICE

RESULTS: ACOUSTIC

females prefer complex calls

Puzzle of choice: why are elaborate and behaviours common

- they are preferred by mates

- there is selection for elaboration

why are elaborate preferred: HYPOTHESIS

direct benefits:

involve direct natural selection on the individual making the choice. Chooser produces more offspring

indirect benefits:

involve genetic benefits to offspring of the individual making the choice. Chooser's offspring are of higher genetic quality (i.e., are more fit)

female choice: direct benefits

- choosiness based on resources (e.g., parentalinvestment) rather than the apparent male attributes

- Male trait is indicator or badge of those resources

Selection for male traits as indicators of resource provisioning or other direct benefits

- territory quality

- defense

- parental care

- lack of parasites (STIs)

FEMALE CHOICE-Indirect benefits:

- females prefer male traits which indicate high genetic quality (good genes)

- if indirect benefit exists then offspring from mating with preferred males should have higher fitness

BROADENING our view on parental investment (Trivers):

When males invest a lot, relative to females, then we predict:

- male choice

- female/female competition

Pipefish sex roles and mating system

- males success limited by brood pouch

- female limitted by access of brood pouch

- females compete for mates

- sexual selection on

1) female size

2) ornamentation

Environmental effects on relative PI and mate choice in Katydids

- decline in ambient resources equal decline in male availability

- predictions at low resources:

male choice of females

female/female comp.

Experiment: in vitro fertilization: How do alternative reproductive strategies influence female choice?

Parental males offer a direct benefit to females: defend nests, provide care to young

&

Satellite and sneaker males offer an indirect benefit to females: "good genes" lead to offspring growing faster, surviving better

But, parental males adjust their level of care when they sense offspring have been sired by other males.

Experiment: in vitro fertilization: RESULTS

female bluegill sunfish face a trade-off in mate choice:

direct benefits: good care

indirect benefits: good genes

Sexual selection may favour ..

- traits with direct benefits

- traits with indirect benefits

SOCIAL BEHAVIOUR

the interaction with - and responses to - otherindividuals of the same species

social behaviour- cooperation

Behaviour that if adopted by two (or more)individuals, benefits both

social behaviour- altruism

Behaviour increases another individual's fitness(survival or reproductive success) at a cost to one's own fitness

cooperation explained by natural selection

shared direct benefits

- cooperation generates IMMEDIATE benefits

ex: cooperative breeding

game theory

- some players

- set possible stratigies

- pay off schedule for playing A vs B, and all B and B

Hawk-Dove game

context between 2 to obtain a resource

2 stratigies

hawk: aggresive

dove- peace

Prisoner's Dilemma

- best strategy is "tit for tat"

- evolution of reciprocity

Prisoners dilemma- tit for tat

I. Cooperate on the first encounter• 'nice' to start

II. Copy your opponents last move thereafter

• 'retaliate' if partner cheats

• 'forgive' if partner has cheated in the past,

but then starts to cooperate

cooperation (tit/tat/iterated) example:

predator inspection

primer on relatedness

more likely to cooperate if related

Altruism directed toward a random individual

non-altruists do best

Altruism directed toward a genetic relative

altruists might do best

Hamilton's rule

when C < r x B

C = cost to the altruistic party

r = genetic relatedness

B = fitness benefit to recipient of altruism

we expect greater altruism to be directed towards closer genetic relatives (br > c)

Fruiting body production in the social amoeba:

Social amoebae discriminate kin from non‐kin and co‐aggregate more with genetically similar individuals!

CONFLICT:

occurs when offspring and parent weight costs/benefits differently

Parent‐Offspring Conflict

- Offspring begs for food

- Parent provides the food

parent-offspring conflict: trade off

fitness of focal offspring vs number of future offspring

ffspring should maximize

B(p) ‐ ½ C(p)

Parents should maximize

½ B(p) ‐ ½ C(p)