Let"s gain Started exactly how Organisms Respond come External factors How populaces Respond to External factors How neighborhoods Respond to external Factors inspect Your expertise

Let"s check out the responses that organisms, populations, and communities to various alters in their outside environment. Before you gain started, don’t forget to publish out your OnTRACK biologic Journal.

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TEKS Standards and also Student Expectations

B(11) The student knows that biological systems work to attain and preserve balance. The student is supposed to: 

B(11)(B) investigate and analyze exactly how organisms, populations, and communities answer to external factors

Learning Objectives

Identify and also give instances of stimuli and responses.

Describe responses the organisms, populations, and communities to assorted stimuli.

Relate stimulus/response to the health and also survival that organisms, populations, and communities.

Essential Questions

How execute organisms, populations, and also communities answers to alters in the external environment?

Why carry out organisms, populations, and communities answer to changes in the external environment?


StimuliResponseAestivationAbioticBioticLimiting FactorsCarrying CapacityMigrationReproductive MigrationSeasonal Migration 


Living points respond to changes in your environments. Imagine the you woke up this morning come the sound the thunder. When you looked outside, girlfriend saw huge dark clouds in the sky. Friend hear one more boom of thunder and see a flash of lightning in the distance. Once you walk the end the door to go to school, girlfriend grab an umbrella. By grabbing the umbrella, you responded to external factors, or stimuli.

Anything that provokes a an answer in an biology is dubbed a stimulus. A stimulus have the right to be external, an interpretation it occurs outside the organism, like the sound that thunder and the speed of lightning. A economic stimulation can likewise be internal, or from within the biology itself, like thirst or hunger. Both external and internal stimuli can reason a response, or reaction, indigenous an organism.

External Stimuli


Organisms answers to external stimuli to maintain homeostasis. Every organism has its own range of tolerance. When an environmental condition (such as temperature) goes over or listed below an organism’s optimal range, the biology experiences stress and responds come the stimulus.

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Have you ever seen a lizard sit in the sun prefer the one pictured here? The hot sun is an external stimulus. The lizard responds to the economic stimulation by aestivating. Aestivation is a state that dormancy practiced by particular organisms to conserve energy and retain water.