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Adaptive Value of Behavior KEY CONCEPT Behavior lets organisms respond rapidly and adaptively to their environment. Adaptive Value of Behavior Behavioral responses to stimuli may be adaptive. • Behavior – any action that an individual carries out in response to a stimulus or to the environment • Internal stimuli tell an animal what is occurring in its own body. – hunger – thirst – pain Adaptive Value of Behavior • External stimuli give an animal information about its surroundings. – sound – sight – changes in day length or temperature Adaptive Value of 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. Adaptive Value of Behavior • Kinesis and taxis are two types of movement-related behaviors. – Kinesis is an increase in random movement. – Taxis is movement in a particular direction. Adaptive Value of Behavior 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. Adaptive Value of 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 Adaptive Value of Behavior • Behaviors may occur daily, monthly, seasonally, or annually. – Hibernation - an animal enters a seasonal dormant state. • Estivation – Animal dormancy during times of heat & dryness – Migration - animals move seasonally from one portion of their range to another. Instinct and Learning KEY CONCEPT Both genes and environment affect an animal’s behavior. Instinct and Learning 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 Instinct and Learning • Many innate behaviors are triggered by a releaser. – releaser is a simple signal: touch, sight, sound, scent – herring gulls chicks and red dot releaser – environmental factors can affect innate behaviors Instinct and Learning Many behaviors have both innate and learned components. • Learning takes many forms. • Habituation occurs when an animal learns to ignore a repeated stimulus. • Imprinting is a rapid and irreversible learning process. – critical period – Konrad Lorenz and graylag geese Instinct and Learning • 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 Instinct and Learning 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. Instinct and Learning • There are two types of conditioning. – Classical conditioning: previously neutral stimulus associated with behavior triggered by different stimulus – Ivan Pavlov and salivating dog – Operant conditioning: behavior increased or decreased by positive or negative reinforcement – B.F. Skinner and “Skinner boxes” Evolution of Behavior KEY CONCEPT Every behavior has costs and benefits. Evolution of Behavior 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 Evolution of Behavior • Behavioral costs can be divided into three categories. – energy costs – opportunity costs – risk costs Evolution of 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. – benefits: control resources – costs: energy and time Evolution of Behavior • 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 Social Behavior KEY CONCEPT Social behaviors enhance the benefits of living in a group. Social 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 chance of predation – costs: increased visibility, competition, disease contraction • Group living requires learning social structure and membership. Social Behavior Social behaviors are interactions between members of the same or different species. • Animals use communication to keep in contact. – visual – sound – touch – chemical Social 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. Social 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 Social Behavior • In altruism, an individual reduces its own fitness to help other members of its social group. – inclusive fitness – kin selection Social Behavior 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.