A change in an organism’s surroundings that causes the organism to react.
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Transcript of A change in an organism’s surroundings that causes the organism to react.
![Page 1: A change in an organism’s surroundings that causes the organism to react.](https://reader036.fdocuments.us/reader036/viewer/2022062309/5697bfe91a28abf838cb7030/html5/thumbnails/1.jpg)
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A change in an organism’s surroundings that causes the organism to react.
![Page 3: A change in an organism’s surroundings that causes the organism to react.](https://reader036.fdocuments.us/reader036/viewer/2022062309/5697bfe91a28abf838cb7030/html5/thumbnails/3.jpg)
External Stimulus
Stimulus occurring on the outside
Example: sun causes you to squint your eyes
Internal Stimulus
Stimulus occurring on the inside
Example: you get goose bumps because you are cold
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a reaction to a stimulus
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A plant’s response to a stimulus
Three types of Tropisms are:
Geotropism
Phototropism
Thigmotropism
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the way a plant grows or bend in response to the Earth (or gravity).
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the way a plant grows or bend in response to light.
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Thigmotropism
the way a plant grows or bend in response to touch
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A plant’s response to water
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Responses can be positive or negative.
A Positive response is when the plant moves toward the stimulus
A Negative response is when a plant moves away from the stimulus
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Roots respond positively to gravity by growing down into the soil
Trunk and branches respond positively to light by growing toward the light
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Trunk and branches respond negatively to gravity by growing up toward the sky
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The pressure of the cell contents against the cell wall
A force is exerted on the cell wall that keeps the plant rigid
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NO TURGOR PRESSURE TURGOR PRESSURE
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