Question

Lots of things require balance: riding a bike, walking a balance beam, jumping rope. Losing balance can cause us to get hurt. The same is true for living things. Plants and animals must maintain an internal balance to stay healthy. Living things have internal communication systems that help to keep things in homeostasis or balance. A stimulus is any change in an organism’s environment that causes the organism to react. The change can be internal or external. For example, when you get hot, you move to the shade. The heat is an external stimulus and moving to the response is the response you make to cool off or come back to homeostasis. If you get hungry, you eat a snack. The hunger is an internal stimulus. Eating a snack is your response.

Which of these is a response to an external stimuli? Select ALL that apply.


A.) hibernation
B.) phototropism
C.) wilting
D.) thirst
E.) dormancy

Answer 1

From the options, the responses to external stimuli are:

B.) phototropism

C.) wilting

D.) thirst

Hibernation, dormancy, and wilting can be responses to internal changes or imbalances that an organism needs to respond to in order to maintain homeostasis.

Phototropism, the movement of plants in response to light, and thirst, the desire to drink in response to dehydration, are direct responses to external environmental stimuli.

So the correct options are:

B.) phototropism

C.) wilting

D.) thirst

Answer 2

The following option is a response to an external stimulus:

B.) Phototropism - Phototropism is a response to the external stimulus of light. Plants move or grow towards or away from a light source in response to changes in the environment.

C.) Wilting - Wilting is also a response to external stimulus such as lack of water or excessive heat, which can cause plants to lose water and become flaccid.

D.) Thirst - Thirst is a response to the external stimulus of dehydration or lack of water in the body.

Therefore, the options B, C, and D are responses to an external stimulus.

A) Hibernation and E) Dormancy are responses to internal stimuli or changes within the organism's body, rather than external stimuli.