Transcript Response to Change


A change in an organism’s
surroundings that causes the
organism to react.
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
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External Stimulus
Stimulus occurring on
the outside
Example: sun causes
you to squint your
eyes

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Internal Stimulus
Stimulus occurring
on the inside
Example: you get
goose bumps
because you are cold

a reaction to a stimulus
A
plant’s response
to a stimulus
Three types of Tropisms are:

Geotropism
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Phototropism

Thigmotropism

the way a plant grows or bend in
response to the Earth (or gravity).
 the
way a plant grows or
bend in response to light.
Thigmotropism
 the
way a plant
grows or bend
in response to
touch
A
plant’s response to water
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

Roots respond positively to
gravity by growing down into
the soil

Trunk and branches respond
positively to light by growing
toward the light

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
NO TURGOR PRESSURE
TURGOR PRESSURE