1. Homeostasis and Behavior

2. Every organism constantly interacts with its environment.

3. stimulus
vocabulary
word!
stimulus - anything that causes a reaction or change in an organism.
Example: An animal is cold so it moves into the
sun.
Example: Getting a drink when you are thirsty.

4. response response - an organisms reaction to a stimulus.
vocabulary
word!
response - an organisms reaction to a stimulus.
Example: An animal is cold so it moves into the sun.
Example: Getting a drink when you are thirsty.

5. Environments change all of the time.
External conditions like weather change
Internal conditions like hydration and hunger change

6. homeostasis – maintaining a stable balance in the body.
vocabulary
word!
homeostasis – maintaining a stable balance in the body.
Organisms’ bodies constantly respond to stimuli to maintain homeostasis.

7. How are stimuli detected?
All organisms are able to detect changes in and around them and to respond to them.

8. external stimulus
vocabulary
word!
external stimulus – stimulus coming from outside an organism.
light, touch, water, gravity, electricity, temperature, darkness etc…

9. Examples: 1. You feel cold so you put on a jacket.
2. A snake lunges at a rabbit so it runs away.
3. It is a very hot, sunny day so a dog sits in the
shade.

10. internal stimulus
vocabulary
word!
internal stimulus – a stimulus coming from inside an organism.
chemicals and hormones

11. Examples: 1. You feel hungry so you eat some food.
2. A cat feels thirsty so it drinks water.
3. A dog feels sick so it’s body triggers a fever.

12. Where do responses come from?
When a stimulus is detected, the nervous system gathers the information.
Then it decides how to respond
quick – nerve impulses
slow - hormones

13. responses taxis – an animal’s movement toward or away from a stimulus.
vocabulary
word!
taxis – an animal’s movement toward or away from a stimulus.
tropism – a plant’s movement toward or away from a stimulus.

14. To maintain homeostasis, organisms must constantly respond to external and internal stimuli.
behavior - set of actions taken by an organism in response to a stimulus.
fight or flight
finding food
hibernation
migration
food storage
dormancy
vocabulary
word!

15. fight or flight
Many animals must decide to fight or flee when in danger.
The body produces adrenaline to prepare them.
The heart and breathing rates increase.

16. finding food and shelter
living organisms must have a food source and a place to live.
hunger is an internal stimulus
most organisms live where they can find food

17. migration
vocabulary
word!
migration – mass movement of a species toward resources like food, water or warmer temperatures.

18. hibernation
vocabulary
word!
hibernation – deep sleep during which an animal slows all of its body processes to save energy.
estivation – deep sleep during hot temperatures which an animal slows all of its body processes to save energy.

19. plant strategies
Plant are not able to migrate so they use different techniques to survive.
food storage – plants can store food in bulbs or tubers (onions and potatoes).
dormancy – plant temporarily stops growing. Some also shed leaves.

20. Homeostasis
An organisms response to internal and external stimuli helps to maintain homeostasis
Homeostasis – balance or equilibrium inside a living organism
Blood sugar levels
Sweating/shivering
Fever
Vomiting
Plant tropisms

21. Blood Glucose Levels
In order to maintain homeostasis, your body tries to keep a certain blood glucose level
When blood glucose is low, you should eat
When blood glucose is high, your pancreas should release insulin
Problems with this system can create diabetes

22. Pill Bugs