27.1 Adaptive Value of Behavior KEY CONCEPT Behavior lets organisms respond rapidly and adaptively to their environment

27.1 Adaptive Value of Behavior

KEY CONCEPT Behavior lets organisms respond rapidly and adaptively to their environment.


Behavioral responses to stimuli may be adaptive.

• Detecting and responding to stimuli is key to an individual’s survival.

• Internal stimuli tell an animal what is occurring in its own body.– hunger– thirst– pain


• External stimuli give an animal information about its surroundings.– sound– sight– changes in day length or temperature


• Specialized cells that are sensitive to stimuli detect sensory information.– information is transferred to the nervous system– nervous system may activate other systems in response

• Animal behaviors help to maintain homeostasis.


• Kinesis and taxis are two types of movement-related behaviors.– Kinesis is an increase in random movement.

– Taxis is movement in a particular direction.


Internal and external stimuli usually interact to trigger specific behaviors.

• Most behaviors are a response to both internal and external stimuli.

• External stimuli may trigger internal stimuli.• Green anole reproductive behavior is triggered by internal

and external stimuli.


Some behaviors occur in cycles.

• A circadian rhythm is the daily cycle of activity.– occurs over 24-hour period– run by a biological clock


• Behaviors may occur daily, monthly, seasonally, or annually.– During hibernation, an animal enters a seasonal dormant

state.


• Behaviors may occur daily, monthly, seasonally, or annually.

– During migration, animals move seasonally from one portion of their range to another.

– During hibernation, an animal enters a seasonal dormant state.


KEY CONCEPT 27.2Both genes and environment affect an animal’s behavior.


Innate behaviors are triggered by specific internal and external stimuli.

• An instinct is a complex inborn behavior.• Instinctive behaviors share

several characteristics.– innate, or performed

correctly the first time– relatively inflexible


– releaser is a simple signal: touch, sight, sound, scent

– herring gulls chicks and red dot releaser

– environmental factors can affect innate behaviors

• Many innate behaviors are triggered by a releaser.


Many behaviors have both innate and learned components.

• Learning takes many forms.• Habituation occurs

when an animallearns to ignore arepeated stimulus.

• Imprinting is a rapidand irreversiblelearning process.– critical period– Konrad Lorenz

and graylaggeese


• In imitation, animals learn by observing the behaviors of others.– young male songbirds

learn songs by listening to adult males

– snow monkeys and potato-washing behavior


Learning is adaptive.

• Animals that can learn can better adapt to new situations.• In associative learning, a specific action is associated with

its consequences.• Conditioning is one type of associative learning.


• There are two types of conditioning.– Classical conditioning: previously neutral stimulus

associated with behavior triggered by different stimulus– Ivan Pavlov and salivating dog


• There are two types of conditioning.– Operant conditioning: behavior increased or decreased

by positive or negative reinforcement– B.F. Skinner and “Skinner boxes”


KEY CONCEPT 27.3Every behavior has costs and benefits.


Even beneficial behaviors have associated costs.

• The benefits of a behavior are increased survivorship and reproduction rates.– both increase an individual’s fitness– both have costs


• Behavioral costs can be divided into three categories.– energy costs– opportunity costs– risk costs


Animals perform behaviors whose benefits outweigh their costs.

• Behaviors evolve only if they improve fitness.• Territoriality refers to the control of a specific area.

– benefits: control resources– costs: energy and time


• Optimal foraging states that natural selection favors behaviors that get animals the most calories for the cost.– benefits: amount of energy gained– costs: energy used to search for, catch, and eat food;

risk of capture; time


KEY CONCEPT 27.4Social behaviors enhance the benefits of living in a group.


Living in groups also has benefits and costs.

• Social behaviors evolve when the benefits of group living outweigh its costs.– benefits: improved

foraging, reproductive assistance, reduced chance of predation

– costs: increased visibility, competition, disease contraction

• Group living requires learning social structure and membership.


Social behaviors are interactions between members of the same or different species.

• Animals use communication to keep in contact.– visual – sound – touch – chemical


• Courtship displays are used to evaluate the fitness of a potential mate.

• Defensive behaviors are used to protect the individual and/or the group.


Some behaviors benefit other group members at a cost to the individual performing them.

• There are many types of helpful social behavior.– cooperation– reciprocity – altruism


• In altruism, an individual reduces its own fitness to help other members of its social group.– inclusive fitness– kin selection


Eusocial behavior is an example of extreme altruism.

• Eusocial species live in large groups of mostly nonreproductive individuals.– haplodiploid species: social insects (wasps, bees, ants)

Queen Minor worker Major worker

– diploid species: termites, snapping shrimp, naked mole rats

• Eusocial behaviors likely evolve by kin selection.


KEY CONCEPT 27.5Some animals other than humans exhibit behaviors requiring complex cognitive abilities.


Animal intelligence is difficult to define.

• Cognition is the mental process of knowing through perception or reasoning.

• Other factors affecting an animal’s behavior may seem like cognition.

– awareness– ability to judge– ability to solve complex problems


Some animals can solve problems.

• Insight is the ability to solve a problem mentally without repeated trial and error. – observed in primates, dolphins, and corvids– chimpanzee retrieving hanging bananas


• Tool use helps an animal accomplish a task.– some dolphins use sponges to protect and hunt– crows and chimpanzees make probing sticks– capuchin monkeys use rocks to crack nuts


Cognitive ability may provide an adaptive advantage for living in social groups.

• Intelligence in animals seems to be correlated with two characteristics.– relatively large brains for their body size– live in complex social groups


• Cultural behavior spreads through a population by learning, not by selection.– taught to one generation by another– aided by living in close proximity

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27.1 Adaptive Value of Behavior KEY CONCEPT Behavior lets organisms respond rapidly and adaptively to their environment