Behavioral responses to stimuli may be adaptive

• 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 Both genes and environment affect an animal’s behavior.