Transcript Stimulus and Response

What is a stimulus?
Stimulus: any change in an
organism’s environment that
causes the organism to react. It
is a fancy way of saying “cause”.
Stimulus – singular
Stimuli – plural
Example: An animal is cold so it moves into
the light.
What is a response?
Response: how the organism
reacts to a stimulus and results in
a change in behavior. It is a
fancy way of saying “effect”
Example: Getting a drink when you are
thirsty.
Examples of stimuli and
their responses.
•
•
•
•
•
You are hungry so you eat.
A rabbit gets scared so it runs away.
You are cold so you put on a jacket.
A dog is hot so he lies in the shade.
It starts raining so you take an
umbrella.
Write a stimulus and response
that you have experienced
recently. Underline the stimulus
and circle the response.
2 Types of Stimuli
External Stimuli
Or
Internal Stimuli
External Stimulus
External stimulus: a stimulus that
comes from outside an organism.
Examples:
1. You feel cold so you put on a jacket.
2. A snake lunges at a rabbit so it runs away.
3. A dog feels hot so it gets water.
Internal Stimulus
Internal Stimulus: a stimulus that comes
from inside an organism.
Examples:
1. You feel hungry so you eat.
2. A cat feels thirsty so it drinks water.
3. You sweat because you are hot.
Internal Stimulus – Wilting in plants
Wilting refers to the loss of rigidity of nonwoody parts of plants (leaves).
Plants wilt because of
1. Over watering: Most common in indoor
plants.
2. Lack of water: Plants need water.
3. Root bound plants: move the growing
plant to another container.
4. Too much sun
5. Not enough sun
6. Too much fertilizer
7. Disease
Internal Stimulus: Vomiting in humans
Vomiting is
•
the forceful expulsion of the contents of one's
stomach through the mouth and sometimes the
nose.
It is a response to internal stimuli such as:
1. Drugs
2. Pain and Stress
3. Motion sickness
4. Food poisoning
5. Excessive consumption of alcohol
6. Eating disorders (eg: bulimia)
Make a T-Chart on your paper and label
the columns internal and external. Put the
letter of each stimulus in the proper
column
A. You have a stomach ache and decide to lay
down.
internal
B. A bird is thirsty and drink some water.
internal
C. A squirrel sees a cat and runs up a tree. external
D. A lion gets hungry and eats a gazelle. internal
E. You see a spider and scream.
external
Tropism – The growth response
of a plant toward or away from a
stimulus
• Phototropism – the way a plant grows
or bends in response to light.
• Geotropism – the way a plant grows or
bends in response to gravity.
• Hydrotropism – the way a plant grows
or bends in response to water.
• Thigmotropism – the way a plant
grows or bends in response to touch.
Assessment
• 1. What is the difference between
a stimulus and a response?
• 2. Vomiting is what type of
stimulus?
• 3. Wilting in plants is what type of
stimulus?
Positive vs Negative Tropism
• Positive Tropism: Going toward the
stimulus.
– Example: If a plant grows toward the stimulus
(light, earth, water, etc.) it shows a positive
tropism.
• Negative Tropism: Going away from a
stimulus.
– Example: Roots grow downwards showing
negative tropism to light.
Phototropism
Positive: Leaves and Stem
because it is going toward the
light source.
Negative: Roots because it
is going away from light
source.
Hydrotropism
What is positive hydrotropism?
Roots
What is negative
hydrotropism?
Leaves and stem
Geotropism
What is the
positive
geotropism?
Roots
What is the
negative
geotropism?
Stem and
leaves
Assessment
1. Identify the external response from the
following.
A.
B.
C.
D.
Your muscle sores when you run a mile
You drink water when you are thirsty
You run away when you see a tiger
After school you eat when you are hungry
2. Which part of the plant shows positive
geotropism?
A.
B.
C.
D.
Leaves
Stems
Flower
Roots
3. Which of the following is not an external
stimulus dealing with plants?
A.
B.
C.
D.
Light
Touch
Gravity
None of the above
4. In the word phototropism, what is the
stimulus?
A.
B.
C.
D.
Touch
Light
Water
None of the above
5. If the plants is placed upside down and
allowed to grown, in what direction would
the roots grow?
A.
B.
C.
D.
Up
Down
Sideways
Not grow
6. If the plants were tilted and allowed to
grow sideways, in what directions would
the leaves and stem grow?
A.
B.
C.
D.
Up
Down
Sideways
None of the above
Assessment
7. Write an example of a stimulus
and response.
8. Give an example of positive
phototropism.
9. Give an example of positive
geotropism.
10. What is thigmotropism?