1. How do organisms react to their environment?
Stimulus - Response
How do organisms react to their environment?

2. What is a Stimulus?
A change in an organism’s surroundings that causes the organism to react.
For example:
A light shining in your eye
A cat running in front of a dog
Thirst
Wind

3. There are two types of stimuli
INTERNAL STIMULUS:
Stimulus that comes from inside the organism
Examples: Hunger, thirst, fever
EXTERNAL STIMULUS:
Stimulus that comes from outside the organism
Examples: light, sound, temperature of environment

4. What is a Response?
An action or change in behavior caused by a stimulus
Examples: Running away, chasing a cat, drinking water, sweating, pupils dilating

5. Specific Responses in Plants
Phototropism- plants growing towards sunlight
Geotropism- plants’ response to gravity. Roots always grow down, and shoots always grow up.

6. Specific responses in cells
Turgor Pressure: plant’s ability to hold enough water in the plant, which allows a plant to stay upright.
What stores water in
plant cells?
Vacuoles!