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Response to Change

Response to Change. Stimulus. A change in an organism’s surroundings that causes the organism to react. 2 Types of Stimulus. External Stimulus Stimulus occurring on the outside Example: sun causes you to squint your eyes. Internal Stimulus Stimulus occurring on the inside

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Response to Change

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  1. Response to Change

  2. Stimulus • A change in an organism’s surroundings that causes the organism to react.

  3. 2 Types of Stimulus • 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

  4. Response • a reaction to a stimulus

  5. Tropism • A plant’s response to a stimulus Three types of Tropisms are: • Geotropism • Phototropism • Thigmotropism

  6. Geotropism • the way a plant grows or bend in response to the Earth (or gravity).

  7. Phototropism • the way a plant grows or bend in response to light.

  8. Thigmotropism • the way a plant grows or bend in response to touch

  9. Hydrotropism • A plant’s response to water

  10. 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

  11. Examples of a positive response • Roots respond positively to gravity by growing down into the soil • Trunk and branches respond positively to light by growing toward the light

  12. Example of a negative response: • Trunk and branches respond negatively to gravity by growing up toward the sky

  13. Turgor Pressure • The pressure of the cell contents against the cell wall • A force is exerted on the cell wall that keeps the plant rigid

  14. Examples No Turgor Pressure Turgor Pressure

  15. Inside a Cell

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