Ch11: Evolution and Behavior

behavior

-performed in an attempt to increase fitness

-includes: feeding behavior, conflict, aggression, courtship, mate-choice, breeding, communication

feeding behavior

-preference for sugar content in sweet foods has an upper limit, whereas preference for fat content does not have an upper limit

-ex: crabs will choose mussels that give the highest calorie return for their effort

innate behaviors (instincts)

-behaviors that do not require any environmental input to develop

-present in all individuals of a population

-do not vary greatly between individuals

fixed action pattern

-special type of innate behavior; a sequence of behaviors triggered in response to a specific signal called a sign stimulus

-requires no learning

-does not vary between individuals

-once started, pattern runs to completion

examples of animal fixed action patterns

1. egg retrieval in geese

2. aggressive displays and attacks by stickleback fish

learned behaviors

acquired and modified over time in response to past experiences

prepared learning

when behaviors are learned easily by all, or nearly all, individuals

the evolutionary basis for prepared learning

-organisms are well prepared to learn behaviors important to ancestor’s fitness

-ex: captive monkeys learn to fear snakes more easily than flowers and rabbits

-ex in humans: language

complex-appearing

___________ behaviors don’t require thought in order to evolve

evolutionary psychology

-a synthesis of evolutionary biology and psychology

-evolutionary psychologists view human brain, behaviors, and emotions as traits produced by natural selection

altruistic behaviors

-kindness, selfless concern for the well-being of others

-come at a cost to the individual performing them, while benefitting a recipient

-Darwin believed natural selection generally worked to produce selfish behavior, not this

kin selection

-an individual assists a close relative to increase the relative’s fitness which offsets the individual’s own decrease in fitness

-the less closely related two individuals are, the more likely they are to experience conflict

reciprocal altruism

-kindness toward unrelated individuals

-increase their fitness for a return of the favor in the future

inclusive fitness

reproductive output individuals bring about through their seemingly altruistic behaviors toward their close kin

reciprocal altruism

-human friendship

-may be enhanced because we: 1) have long lifespans, 2) can recognize faces, 3) can keep track of cheaters

-humans may keep track of social information to identify those who are good candidates for reciprocal altruism

what must be met for reciprocal altrusim?

1. repeated interactions with opportunities to be both the donor and recipient

2. benefits of the recipient are greater than the costs to donor

3. an ability to recognize and punish cheaters

evolutionary mismatch

-an organism possesses traits that are evolutionarily adapted to an ancestral environment (you get nothing in return)

-craving sugar and fat

-charitable contributions to people in distant places

-alarm calling in transplanted squirrels

group selection

-evolution leads to behaviors good for the species or population but decrease the fitness of individuals exhibiting the behavior

-selfish genes win, but this never does

reproductive investment

female ___________ exceeds the males in all animals because the female produces larger gametes, immobile and produced in fewer numbers

increases

the total reproductive output for males ______ with every new female mated

females

the total reproductive output for _______ does not increase by mating with additional males beyond the first

survival

female reproductive success is increased by increasing parenting effort to ensure _______ of offspring

vulnerable

males and females are _________ at different stage of the reproductive exchange

secure

competition and courtship can help males and females _____ reproductive success

four general rules influence female choosiness

1. mate only after subjecting a male to courtship rituals; many bird species

2. mate only with a male who controls valuable resources; territorial defense

3. 3.mate only with male who contributes a large parental investment up front; nuptial gifts

4. mate only with a male that has a valuable physical attribute; physical feature is an indicator of the relative quality of the male

offspring

to be evolutionary successful, your ________ must survive

mate guarding

-helps ensure paternity

-protects reproductive investments

copulatory plug

-method of mate guarding

-coagulated sperm and mucus

-reptiles, insects, many mammals

what complicates mating systems?

1. differences between animals’ mating behavior and bonding behavior

2. mating system variation within the species

3. males and females often differ in their mating behavior

pair bond

characterized by a male and female spending a high proprotion of time together; appears monogamous

monogamy

most individuals mate and remain with just one other individual

polygamy

when some individuals attract multiple mates while other individuals attract more

polygyny

individual males mate with multiple females

polyandry

individual females mate with multiple males

parental investment in birds

-roughly equal

-leads to monogamous mating behavior

behaviors associated with sexual dimorphism

-one parent invest in caring more for offspring

-mating system tends toward polygamy

-one sex is choosier when selecting a mate

-one sex competes for access to mating

behaviors associated with sexual monomorphism

-both parents invest equally in caring for the offspring

-mating system tends toward monogamy

-both sexes are equally choosy when selecting a mate

communication

an action or signal from one individual that informs or alters the behavior of another

most common signals used by animals to communicate:

chemical, acoustic, visual

chemical communication

pheromones released by one individual and detected by another can trigger behavioral responses

acoustic communication

sounds, such as a lion’s roar, are a common method of triggering behavioral responses

visual communication

when a puffer fish puffs up its body in response to a predator

language

-assigns arbitrary symbols to represent concepts and has a system of grammar

-examples: honeybee waggle dance to food source, vervet monkey alarm call for predator threat, nonhuman primates use signs and hand signals

honest signal

-conveys accurate information; cannot be fake when the signaler and receiver have the same interestss

deception

-dishonest signaling can evolve when one animal can increase its fitness by deceiving another