Stimulus and Response in Biology
This page introduces the fundamental concepts of stimulus and response in living organisms, explaining how they interact with their environment and internal conditions.
Definition: A stimulus is a thing or event in the environment that causes a response in an organism.
Vocabulary: The plural form of stimulus is "stimuli".
The relationship between stimulus and response is crucial for an organism's survival and adaptation. When an organism detects a stimulus, it reacts with an appropriate response.
Example: Feeling thirsty (internal stimulus) leads to the response of getting a drink.
Definition: A response is how an organism reacts to a stimulus.
Example: An animal feeling cold (stimulus) moves into the sun (response).
The page also distinguishes between external and internal stimuli:
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External Stimuli: These come from outside the organism.
Examples: Temperature changes, presence of predators, availability of food
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Internal Stimuli: These originate from within the organism.
Examples: Infections, dehydration, lack of energy, pain
Highlight: The pupil's response to light is a classic example of stimulus and response. Bright light causes the pupil to contract, while dim light causes it to dilate.
The page concludes with a detailed diagram illustrating the pathway of a visual stimulus through the eye and nervous system, demonstrating how the body processes and responds to external stimuli.
Example: A bright light (stimulus) enters the eye, triggering a series of neural responses that ultimately cause the pupil to contract (response).
This comprehensive overview provides a solid foundation for understanding how organisms respond to external stimuli, a key concept in biology that helps explain why living things respond to stimuli and how they maintain homeostasis in changing environments.
