7.13AB: External and Internal Stimuli
Organisms and Environments
Using the Web Surfing Science websites your teacher has assigned to you, complete
the following online treasure hunt.
Part I: External Stimulus - Plants
Choose Tropisms movies to view. View “Cool Corn Phototropism” to answer the questions.
1. How did the plants respond to the light source in the center of the planting area?
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2. How did the plants respond to the more diffuse room lights?
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3. What form of tropism is creating the stimulus with the single light source?
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4. What form of tropism is creating the stimulus with the diffuse light source?
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View “Corn Root Gravitropism” to answer the following questions.
5. Describe what occurs in the video.
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6. What external stimulus causes the root to grow in such a manner?
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View “Sunflower Gravitropism” to answer the following questions.
7. Describe what occurs in the video.
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8. What external stimulus causes the plants to grow in such a manner?
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7.13AB: External and Internal Stimuli
Organisms and Environments
Part II: External Stimulus - Animals
1. What are two ways various animals respond to the external stimulus of cold weather and
reduced food supply? _______________________
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2. Choose three types of migration from the list below and circle them. Write a description
and give an example of each migration type that you choose.
Seasonal Latitudinal Altitudinal Reproductive
Nomadic Removal Complete
Partial Irruptive
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Part III: Homeostasis
1. What are the three internal variables that are concerned with homeostasis?
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2. What is a negative feedback loop?
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3. Different organisms have different ways to maintain body temperature. Name and describe
the two different ways animals maintain their temperatures.
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