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Stimulus & Response

Stimulus & Response . Stimulus. A change in organism’s environment. Types of Stimuli. A stimulus can either be external or internal. Ex ternal stimuli- come from factors found in the environment. Examples- temperature, predators, presence of water or food, etc

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Stimulus & Response

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  1. Stimulus & Response

  2. Stimulus Achange in organism’s environment

  3. Types of Stimuli • A stimulus can either be external or internal. • External stimuli- come from factors found in the environment. Examples- temperature, predators, presence of water or food, etc • Internal stimuli- come from factors within an organism Examples- germs, dehydration, lack of energy, pain

  4. Stimulus Is this stimulus external or internal?

  5. Response An organisms reaction to change.

  6. Response

  7. Homeostasis Homeo- same Stasis- state of balance The purpose of response to stimuli in organisms is to maintain homeostasis, a balance within it’s internal systems.

  8. Examples • Stimulus = Is this internal or external? • Response = • Stimulus = Is this internal or external? • Response = Lack of water Wilting Bacteria or Virus Fever

  9. Tropisms • Tropism = plant’s growth response toward or away from a stimulus

  10. Tropisms • Tropism = plant’s growth response toward or away from a stimulus • Positive tropism • Negative tropism

  11. Tropisms • Tropism = plant’s growth response toward or away from a stimulus • Positive tropism = plant grows toward a stimulus • Negative tropism

  12. Tropisms • Tropism = plant’s growth response toward or away from a stimulus • Positive tropism = plant grows toward a stimulus • Negative tropism = plant grows away from a stimulus

  13. Hydrotropism Hydrotropism = a plant’s rootsgrow toward water Is this positive or negative?

  14. Phototropism Plants grow toward a source of light Animation: http://botanical-online.com/animation8.htm

  15. Examples

  16. Thigmotropism A plant grows toward or away from pressure Positive turns toward pressure Negative turns away from pressure

  17. Geotropism • A plant grows with or against gravity • Also called Gravitropism Positive- A plant’s roots grow down, with the pull of gravity Negative- A plant’s stems or trunk grow up, against the pull of gravity. Animation: http://botanical-online.com/animation4.htm

  18. Regardless of the position a seed is planted in, the roots grow down with gravity and the stem up against gravity. Regardless of the slope of the land, the tree grows up against gravity.

  19. Working Together • Plant tropisms work together to maintain homeostasis within the plant + phototropism + geotropism - geotropism + hydrotropism

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