Turgor Pressure & Tropisms

Front

Stimulus

Back

A detectable change in the internal or external environment of an organism. Plural: Stimuli.

Front

Examples of stimuli

Back

Light, chemicals, gravity, temperature, touch, sound, water, electricity.

Front

Response

Back

Any change an organism makes because of a change in the environment.

Front

Examples of responses in plants

Back

Light: plant bends

Gravity: roots grow down

Touch: responds to physical touch

Water: roots grow toward

Front

Internal Stimulus

Back

From within the organism

Example: a plant wilts, absorbs water, and becomes upright again.

Front

External Stimulus

Back

From outside the organism.

Examples: light, chemicals, gravity, sound, touch, temperature, water, electric field.

Front

Tropism

Back

The turning of all or part of an organism in a particular direction in response to an external stimulus.

Front

Examples of tropisms in plants

Back

Phototropism: light

Geotropism: gravity

Hydrotropism: water

Thigmotropism: touch

Front

Positive Tropism

Back

The organism moves toward the stimulus. Example: a plant grows toward a light source.

Front

Negative Tropism

Back

The organism moves away from the stimulus. Example: a plant grows against gravity.