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Chapter 27: Animal Behavior
KEY CONCEPT Behavior lets organisms respond rapidly and adaptively to their environment. Usually in a beneficial way.Examples?
Plant bends toward light
Pufferfish inflates when threatened
Cat comes when you use a can opener
Toad releases poison when grabbed
Chapter 27: Animal Behavior
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
Chapter 27: Animal Behavior
• External stimuli give an animal information about its surroundings.– sound– sight– changes in day length or temperature
Chapter 27: Animal Behavior
• 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.
Chapter 27: Animal Behavior
• Kinesis and taxis are two types of movement-related behaviors.– Kinesis is an increase in random movement.
Example: Pill bugs increase activity as they dry out to find moist areas
– Taxis is movement in a particular direction either toward or away from a stimuli
–Example: plants growing toward light, deer running away from rustling in the brush
Chapter 27: Animal Behavior
Internal and external stimuli usually interact to trigger specific behaviors.
• Most behaviors are a response to both internal and external stimuli– Combination, not just one stimuli
• External stimuli may trigger internal stimuli.• Green anole reproductive behavior is triggered by internal
and external stimuli.– External: males become aggressive and court females– Internal: females release hormones that make females
receptive• How could internal and external stimuli cause you to wake
up in the morning?
Chapter 27: Animal Behavior
Some behaviors occur in cycles.
• A circadian rhythm is the daily cycle of activity.– occurs over 24-hour period– run by a biological clock
Chapter 27: Animal Behavior
• Behaviors may occur daily, monthly, seasonally, or annually.– During hibernation, an animal enters a seasonal dormant
state.What kind of stimuli might trigger hibernation?
Chapter 27: Animal Behavior
• Behaviors may occur daily, monthly, seasonally, or annually.
– During migration, animals move seasonally from one portion of their range to another.
What kind of stimuli might trigger migration?
– During hibernation, an animal enters a seasonal dormant state.
Chapter 27: Animal Behavior
• Circadian Rhythms survey
Chapter 27: Animal Behavior
KEY CONCEPT Nature vs. Nurture Debate
Both genes and environment affect an animal’s behavior.
Chapter 27: Animal 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– Why would instincts be necessary?– Baby Swimming Reflex
Chapter 27: Animal Behavior
– releaser is a simple signal– herring gulls chicks and red
dot releaser– environmental factors can
affect innate behaviors– Ex: Honey Bees
• Many innate behaviors are triggered by a releaser.
Chapter 27: Animal Behavior
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
Why might this person be wearing this costume?
Chapter 27: Animal Behavior
• In imitation, animals learn by observing the behaviors of others.– young male songbirds
learn songs by listening to adult males
– Children learning to talk– snow monkeys and
potato-washing behavior…younger teaches older
Chapter 27: Animal 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.– Child with a hot stove– Birds with bad-tasting food
• Conditioning is one type of associative learning.
Chapter 27: Animal Behavior
• There are two types of conditioning.– Classical conditioning: previously neutral stimulus
associated with behavior triggered by different stimulus– Ivan Pavlov and salivating dog
Chapter 27: Animal Behavior
• There are two types of conditioning.– Operant conditioning: behavior increased or decreased
by positive or negative reinforcement– B.F. Skinner and “Skinner boxes”
Chapter 27: Animal Behavior
KEY CONCEPT Every behavior has costs and benefits.
Chapter 27: Animal Behavior
Even beneficial behaviors have associated costs.
• The benefits of a behavior are increased survivorship (# of individuals that survive from one year to the next) and reproduction rates.– both increase an individual’s fitness; favored by natural
selection– both have costs
Chapter 27: Animal Behavior
• Behavioral costs can be divided into three categories.
– energy costs: energy not available for other tasks– opportunity costs: time spent cannot be used on another
task– risk costs: need food but risk getting eaten
Some behaviors seem harmful but are beneficial
Chapter 27: Animal Behavior
Animals perform behaviors whose benefits outweigh their costs.
• Behaviors evolve only if they improve fitness.• Territoriality refers to the control of a specific area.
Chapter 27: Animal Behavior
• Optimal foraging states that natural selection favors behaviors that get animals the most calories for the cost.
Ex: Oystercatchers eat mussels…too big and it takes too long and too much energy to open, too small and there’s not enough meat, so the most successful eat the medium mussels
Chapter 27: Animal Behavior
KEY CONCEPT Social behaviors enhance the benefits of living in a group. If you had a choice would you rather live alone or in a group? Why do you think humans live in groups?
Chapter 27: Animal Behavior
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 predation
– costs: increased visibility, competition, disease contraction
• Group living requires learning social structure and membership.
Chapter 27: Animal Behavior
Social behaviors are interactions between members of the same or different species.
• Animals use communication to keep in contact.– Visual: gestures or postures– Sound: Calls of alarm, distress, mating, etc.– Touch: antennae – Chemical: pheromones
Chapter 27: Animal Behavior
• Courtship displays are used to evaluate the fitness of a potential mate.
• Defensive behaviors are used to protect the individual and/or the group.
Chapter 27: Animal Behavior
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
Chapter 27: Animal Behavior
• In altruism, an individual reduces its own fitness to help other members of its social group.– inclusive fitness: total # of genes contributed by relatives
to next generation– kin selection: natural selection acts on survival of close
relatives
Chapter 27: Animal Behavior
Eusocial behavior is an example of extreme altruism.
• Eusocial species live in large groups of mostly nonreproductive individuals.– haplodiploid species: sex determined by # of
chromosomes, 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.
Chapter 27: Animal Behavior
KEY CONCEPT Some animals other than humans exhibit behaviors requiring complex cognitive abilities.
Chapter 27: Animal Behavior
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.– Clever Hans
– awareness– ability to judge– ability to solve complex problems
Chapter 27: Animal Behavior
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
Chapter 27: Animal Behavior
• 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
Chapter 27: Animal Behavior
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
Chapter 27: Animal Behavior
• Cultural behavior spreads through a population by learning, not by selection.– taught to one generation by another– aided by living in close proximity