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Behavioral BiologyChapter 52

Biology Raven and Johnson 7th Ed.

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Outline

• Behavioral Genetics• Learning• The Development of

Behavior• Animal Cognition• Migratory Behavior• Courtship• Communication in

Social Groups

• Behavioral Ecology• Foraging Behavior• Territorial Behavior• Reproductive

Strategies• Sexual Selection• Mating Systems• Altruism• Kin Selection• Social Systems

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Approaches to the Study of Behavior

• Behavior can be defined as the way an organism responds to stimuli in its environment.

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Behavioral Genetics

• Recent studies have shown identical human twins, separated at birth, develop many similarities, even though they were raised in very different environments.

• Behavior may be controlled by one, or many, genes.

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Learning Influences Behavior

• Comparative psychologists focus on learning as the major element that shapes behavior.

– nonassociative learning Animal is not required to form association

between a stimulus and a response.• examples

– habituation - decrease in response to a repeated stimulus with no positive or negative consequences

– sensitization - increased responsiveness to a stimulus

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Learning

• Associative learning– Association between two stimuli or between a

stimulus and a response.• Classical conditioning - Paired presentation of two

different stimuli creates an association between the stimuli (Pavlovian conditioning).

• Operant conditioning - Animal learns to associate its behavioral response with a reward or punishment.

– trial and errorSkinner Box- mice learn to push a lever to release

food. (They will push a lever to get cocaine and ignore

food, sex, and play, until they die.)

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Learning

• Instinct– Investigations have shown some animals

have innate predispositions toward forming certain associations.

Learning preparedness demonstrates that what an animal can learn is biologically influenced.

An animal’s ecology is key to understanding what an animal is capable of learning.

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The Development of Behavior

• Parent-offspring interactions– imprinting - social attachments to other

individuals that will influence behavior later in life (Konrad Lorenz)

sensitive phase or critical period

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Fig. 52.09

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The Development of Behavior

• Interaction between instinct and learning– Genetic templates may guide young birds

to learn appropriate song. During critical period, the template will

accept the correct song as a model.Template is selective, and leaning

plays a role.

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Animal Cognition

What does thinking mean?

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Animal Cognition

• Central question in animal behavior is whether animals show cognitive behavior.

– Do they process information and respond in a manner that suggests thinking ?

Some examples are compelling:chimpanzees ravens

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Fig. 52.15

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Orientation and Migration

• Taxis - movement toward or away from a stimulus

– positive (toward) and negative (away)• Kineses - increase in general activity level

due to increased stimulus intensity• Migrations - long-range, two-way

movements– monarch butterflies

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Orientation and Migration

• Navigation – navigation - ability to set or adjust a

bearing and follow it– orientation - ability to follow a bearing

Inexperienced starlings appear to migrate by orientation, while older birds use true navigation.

magnetic field celestial clues

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Courtship

• Stimulus - response chain in which behavior of one individual in turn releases behavior of another individual

• Courtship signaling– Signals are often species-specific .

Reciprocal responses provide a continuous check on species identity.

Stickleback- see next slide

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Stimulus-Response Chain

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Courtship

• Pheromones and acoustic signals– Pheromones are chemical messengers

used for communication between individuals, and often serve as sex attractants. (in humans egg and sperm—they are from two individuals, right?)

Silk moths are the most famous example.– Many insects, amphibians, and birds

produce species-specific acoustic signals to attract mates.

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Communication in Social Groups

• Communicated information:– alarm calls– alarm pheromones– trail pheromones– dance language

Waggle dance of European honeybee relays direction and distance of a located food source.

– primate vocalizations

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Waggle Dance of Honeybees

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Behavioral Ecology

• Behavioral ecology is the study of how natural selection shapes behavior.

– examines adaptive significance and survival value of behavior

effect on fitness

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Foraging Behavior

• Optimal foraging theory - Natural selection favors individuals feeding on prey that maximize net energy intake efficiency.

– two assumptions: Natural selection will only favor behavior

maximizing energy acquisition if increased energy reserves lead to increases in reproductive success.

Optimal foraging has resulted from natural selection.

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Territorial Behavior

• Territoriality is behavior in which individual members of a species maintain exclusive use of an area containing a limited resource.

– defense against intrusion– made on cost:benefit basis centered

around fitness

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Competition for Space

6 birds species removed (R) were replaced by existing species and by 4 new species (N).

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Parental Investment and Mate Choice

• Mate choice occurs when individuals do not mate at random, but appear to make decisions on mates base on quality.

– common in females, usually they have a larger reproductive investment

• Parental investment refers to contributions each sex makes in producing and rearing offspring.

– usually higher in females– In mormon crickets, the male invests in a high

energy sperm, and the males are more selective.

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Reproductive Competition and Sexual Selection

• Sexual selection occurs when individuals compete for mating opportunities.

– involves both intrasexual and intersexual selection

– leads to evolution of secondary sexual characteristics

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Products of Sexual Selection

a. African paradise whydah b. Peacock c. Eyespots/ Mates

In many species, the boys dress up for the girls : )

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Reproductive Competition and Sexual Selection

• Intrasexual selection– Individuals of one sex compete for the

opportunity to mate with individuals of the other sex.

Selection will strongly favor sexual dimorphism.

– sperm competition

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Intersexual Selection

• Intersexual selection– benefits of mate choice

Males may help rear young, gather food, defend nest, etc..

• Indirect benefits– Females may choose healthiest or oldest

males. overall genetic or physiological health

more vigorous offspring

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Intersexual Selection

– Handicap hypothesis Only genetically-superior males can

survive with a handicap.– Sensory exploitation involves evolution in

males of an attractive signal that exploits preexisting biases.

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Mating Systems

• Number of mates– monogamy - one male and one female– polygyny - one male and many females– polyandry - one female and several males

• Needs of offspring– altricial - require extensive, prolonged care

(ex. Humans)– precocial - require little parental care

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Mating Systems

• Extra-pair copulations -- (cheating)– Researchers found that in one study, 20%

of red-winged blackbird offspring were a result of extra-pair copulations.

may be very pervasiveMales benefit by increased mating

success.Females may benefit by increased

rearing assistance.

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Factors Favoring Altruism and Group Learning

• Altruism - performance of an action that benefits another individual at a cost to the actor (nest helpers)

– Natural selection would seem to argue against altruism.

Such acts may not be truly altruistic, and may be benefiting the actor.

Nest helpers may gain parenting experience or inherit territory.

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Factors Favoring Altruism and Group Learning

• Reciprocity - Individuals may form partnerships in which mutual exchanges of altruistic acts occur. Ex: Vampire bats will share blood with those who have shared with them in the past.

• Kin selection - By directing aid toward close genetic relatives, an altruist may increase reproductive success of its relatives enough to compensate for the reduction in its own fitness.

– The more closely related the individuals, the more likely the potential genetic gain.

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Altruism

• Hamilton’s Rule- Altruistic acts (acts that benefit another member of the same species) are favored when rb > c

• r = relatedness –proportion of shared alleles

• b = benefit• c = cost

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Examples of Kin Selection

• Belding’s ground squirrel – sound alarm calls when spot predators

Females are more likely to call than males because colony is mostly her relatives.

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Group Living - Evolution of Social Systems

• Society - group of organisms of the same species organized in a cooperative manner

• Insects– All ants, some bees, some wasps, and all

termites are eusocial. Eusocial colonies are composed of

different castes of workers that differ in size and morphology and have different tasks to perform.

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Vertebrate Societies

• Vertebrate social groups are usually less rigidly organized and cohesive.

– Some complex systems exhibit both reciprocity and kin-selected altruism.

also display higher levels of conflict and aggression among group members

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Summary

• Behavioral Genetics• Learning• The Development of

Behavior• Animal Cognition• Migratory Behavior• Courtship• Communication in

Social Groups

• Behavioral Ecology• Foraging Behavior• Territorial Behavior• Reproductive

Strategies• Sexual Selection• Mating Systems• Altruism• Kin Selection• Social Systems

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