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Biology Notes
Term [3]
27.1
 Stimulus: A type of information that makes an organism change its behavior.
Internal Stimuli: It tells an animal what is occuring in its own body.
Ex: Hunger, Thirst, Pain.
External Stimuli: It gives an animal information about its surroundings.
Ex: The sound of a predator cause an animal to hide or run away, the sight of a mate trigger courtship
behaviors.
 Epinephrine causes your body to initiate “fight-or-flight” response.
 Muscles are the most obvious organs activated in response to stimuli.
Kinesis: An increase in random movement.
Taxis: A movement in a specific direction, either toward or away from a stimulus.
Ex: Euglena are light-sensitive and will move toward a light source.
Q. How is taxis or kinesis an example of the adaptive nature of behavior?
→ Both behaviors cause an animal to move from a less desirable location to a more desirable location,
thus helping to maintain constant internal conditions.
Q. What might be internal and external stimuli that cause you to wake up in the morning?
→ Hunger and Biological Clock are examples of internal stimuli that wake up the person up.
Alarm Clock and Sunlight are examples of external stimuli that wake the person up.
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Circadian Rhythm: The daily cycle of activity that occurs over a 24-hour period.
Hibernation: A behavior where animals avoid cold winter and into dormant state.
Shorter Days and Cooler Temperatures cause animals to enter hibernation in the fall.
In the spring, Longer Days and Warmer Temperatures cause animals to wake up.
Migration: Allows animals to avoid harsh conditions in their home for a part of the year.
Q. How might climate change affect animal migration patterns?
→ Colder temperatures might cause migration to begin earlier in the year.
F.A.
Q. Why are behavioral responses to stimuli considered to be adaptive?
→ Animals that do respond correctly to a stimulus have a greater chance of survival.
Q. What internal and external stimuli might signal to Alaskan caribou that it is time to migrate?
→ Internal: Hormonal changes.
External: Changes in day length or temperature.
Q. What is the connection between a circadian rhythm and the biological clock?
→ Circadian rhythms are the daily cycles of activity controlled by the biological clock.