Stimulus & Response

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Stimulus Response
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Stimulus

• A change in organisms environment

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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

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Stimulus
Is this stimulus external or internal?
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Response

• An organisms reaction to change.

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Response
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Homeostasis

• Homeo- same
• Stasis- state of balance
• The purpose of response to stimuli in organisms
  is to maintain homeostasis, a balance within its
  internal systems.

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Examples

• Stimulus
• Is this internal or external?
• Response
• Stimulus
• Is this internal or external?
• Response

Lack of water
Wilting
Bacteria or Virus
Fever
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Tropisms

• Tropism plants growth response toward or away
  from a stimulus

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Tropisms

• Tropism plants growth response toward or away
  from a stimulus
• Positive tropism
• Negative tropism

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Tropisms

• Tropism plants growth response toward or away
  from a stimulus
• Positive tropism plant grows toward a stimulus
• Negative tropism

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Tropisms

• Tropism plants growth response toward or away
  from a stimulus
• Positive tropism plant grows toward a stimulus
• Negative tropism plant grows away from a
  stimulus

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Hydrotropism

• Hydrotropism a plants
• roots grow toward water
• Is this positive or negative?

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

• A plant grows toward or away from pressure

Positive turns toward pressure
Negative turns away from pressure
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Geotropism

• A plant grows with or against gravity
• Also called Gravitropism

Positive- A plants roots grow down, with the
pull of gravity
Negative- A plants stems or trunk grow up,
against the pull of gravity.
Animation http//botanical-online.com/animation4.
htm
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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.
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Working Together

• Plant tropisms work together to maintain
  homeostasis within the plant

phototropism
geotropism
- geotropism
hydrotropism