1. TEK 7. 13(13) Organisms and environments
TEK 7.13(13) Organisms and environments. The student knows that a living organism must be able to maintain balance in stable internal conditions in response to external and internal stimuli. The student is expected to:
investigate how organisms respond to external stimuli found in the environment such as phototropism and fight or flight; and
describe and relate responses in organisms that may result from internal stimuli such as wilting in plants and fever or vomiting in animals that allow them to maintain balance.
Big Ideas:
1)  Organisms respond to both internal and external stimuli.
2)  Internal stimuli include hunger, thirst, hormones.
3)  Thirst is a mechanism essential to maintaining fluid balance within an organism.
4)  Hunger is triggered by a release of a hormone in the brain.
5)  External stimuli include presence or absence of heat or light.

2. Texas Essential Knowledge and Skills Statement:
The student knows that a living organism must be able to maintain balance in stable internal conditions in response to external and internal stimuli.
1. Organisms respond to changes in the external environment in order to maintain
balance. We call this balance homeostasis. The change in the external
environment is called a stimulus, and the resulting reaction of the organisms is
called a response.
2. Plants may respond to an external stimulus such as touch, gravity (gravitropism), and light (phototropism).
3. An animal may respond to an external stimulus, such as the presence of a
predator by becoming aggressive or running away (fight or flight).
4. Organisms have an internal announcement system to alert them of hunger, thirst, and temperature extremes to maintain homeostasis.
5. Plants may respond to an internal stimulus such lack of water or other nutrients by either wilting or changing its growth/development.
6. Animals respond to internal stimuli in various ways. Animals will vomit when food is spoiled or contaminated. When pathogens like bacteria or virus invade humans, the body responds by releasing chemicals to raise the core body temperature, causing a fever.

3. 1. What is the difference between a stimulus and a response?
Student Expectation:
The student is expected to investigate how organisms respond
to external stimuli found in the environment such as phototropism and fight or flight and describe and relate responses in organisms that may result from internal stimuli such as wilting in plants and fever or vomiting in animals that allow them to maintain balance.
1. What is the difference between a stimulus and a response?
2. How does changing an external stimulus affect how an organism will respond?
3. In what ways does an organism’s body respond to maintain homeostasis?
4. How do organisms respond internally when unknown pathogens invade the body?

5. an internal warning system to Organisms have
alert them of ________, _______,
and ______________ extremes to
maintain ______________.
burn __________ to
Our bodies
keep up with our ___________
needs.
________________
helps maintain a stable body temperature of about 98.6°F.
The ________________ of sweat returns the body to its original temperature. If an
organism
feels threatened
by an external stimulus,
such as a predator,
it responds by ____________
or _______________ _________.

6. Warm up Stand up and balance on one foot for 3 minutes.
After the timer goes off, sit back down in your seat. Discuss the following questions with your table partners:
What did you notice during this activity?
Did it get more difficult to balance as time went on?
What did you want to do?
You just experienced homeostasis. Your body was trying to keep you upright by maintaining your balance. Homeostasis is regulated by the nervous system.

7. HOMEOSTASIS Output Input Cause Effect Stimulus Response Balance
Organisms respond to changes in their environment in order to maintain balance. We call this balance homeostasis.
Example: The stimulus is being struck with the hammer.
Example: The response is the knee jerk reflex.
Change
Reaction
Output
Input
Cause
Effect
Stimulus
Response
Balance
HOMEOSTASIS

8. Homeostasis (Balance) Complete the “Stimulus” column on your chart.
Response
Homeostasis (Balance)
1. Hunger
2. Thirst
3. Excess body heat
4. Low body temperature
5. Increased Exercise
6. Spoiled Food
7. Bacteria or Virus
8. Predator 9.
10.
11.
Complete the “Stimulus” column on your chart.
You have 2 minutes. 1 2 2 1 5 4 3 6 7 8 9 2 5 6 4 3 1 5 8 4 5 3 2 1 6 7 2 3 1 7 9 4 1 9 1 8 7 5 6 2 3 8 9 7 6 4 5 8 4 3 4 2 9 3 5 1 2 6 9 7 8
Minutes
Seconds

9. Homeostasis (Balance) Complete the “Stimulus” column on your chart.
Response
Homeostasis (Balance)
1. Hunger
2. Thirst
3. Excess body heat
4. Low body temperature
5. Increased Exercise
6. Spoiled Food
7. Bacteria or Virus
8. Predator 9.
10.
11.
Complete the “Stimulus” column on your chart.
You have 2 minutes. 2 5 3 1 4 6 7 8 9 2 5 6 4 3 1 5 9 4 5 3 2 1 6 7 2 3 1 8 7 4 9 1 8 7 5 6 2 3 8 9 7 6 4 5 8 4 3 4 2 1 9 3 5 1 2 6 9 7 8
Minutes
Seconds

10. extremes to maintain homeostasis.
Organisms have an internal warning system to alert them of hunger, thirst,
and temperature
extremes to maintain homeostasis.

11. YELLOW – Our group has a question/
RED – HELP! Our group has a question/problem and we can’t move on until it’s solved!
YELLOW – Our group has a question/
problem and we can keep working while we’re waiting for help.
GREEN – No questions or problems at this time. Yay!

12. Use your prior knowledge of HOMEOSTASIS, EQUILIBRIUM, and BODY SYSTEMS to complete the “Response” and “Homeostasis/Balance” columns for the first four stimuli on your chart. 04 19 20 18 16 21 17 23 27 28 26 25 15 24 22 13 04 05 03 02 00 01 06 07 11 12 10 09 08 14 29 50 51 49 48 46 47 52 53 58 59 57 56 54 55 30 45 35 36 34 33 31 32 44 37 42 43 38 41 40 39
You and your table partners will have FIVE minutes to complete this task.

13. Use your prior knowledge of HOMEOSTASIS, EQUILIBRIUM, and BODY SYSTEMS to complete the “Response” and “Homeostasis/Balance” columns for the first four stimuli on your chart. 03 19 20 18 16 21 17 23 27 28 26 25 15 24 22 13 04 05 03 02 00 01 06 07 11 12 10 09 08 14 29 50 51 49 48 46 47 52 53 58 59 57 56 54 55 30 45 35 36 34 33 31 32 44 37 42 43 38 41 40 39
You and your table partners will have FIVE minutes to complete this task.

14. Use your prior knowledge of HOMEOSTASIS, EQUILIBRIUM, and BODY SYSTEMS to complete the “Response” and “Homeostasis/Balance” columns for the first four stimuli on your chart. 02 19 20 18 16 21 17 23 27 28 26 25 15 24 22 13 04 05 03 02 00 01 06 07 11 12 10 09 08 14 29 50 51 49 48 46 47 52 53 58 59 57 56 54 55 30 45 35 36 34 33 31 32 44 37 42 43 38 41 40 39
You and your table partners will have FIVE minutes to complete this task.

15. Use your prior knowledge of HOMEOSTASIS, EQUILIBRIUM, and BODY SYSTEMS to complete the “Response” and “Homeostasis/Balance” columns for the first four stimuli on your chart. 01 19 20 18 16 21 17 23 27 28 26 25 15 24 22 13 04 05 03 02 00 01 06 07 11 12 10 09 08 14 29 50 51 49 48 46 47 52 53 58 59 57 56 54 55 30 45 35 36 34 33 31 32 44 37 42 43 38 41 40 39
You and your table partners will have FIVE minutes to complete this task.

16. Use your prior knowledge of HOMEOSTASIS, EQUILIBRIUM, and BODY SYSTEMS to complete the “Response” and “Homeostasis/Balance” columns for the first four stimuli on your chart. 00 19 20 18 16 21 17 23 27 28 26 25 15 24 22 13 04 05 03 02 00 01 06 07 11 12 10 09 08 14 29 50 51 49 48 46 47 52 53 58 59 57 56 54 55 30 45 35 36 34 33 31 32 44 37 42 43 38 41 40 39
You and your table partners will have FIVE minutes to complete this task.

17. And
For Understanding

18. Stimulus Response Hunger is an example of homeostasis Our bodies burn
because food is something we need to keep
our bodies balanced and healthy.
Our
bodies burn
Food to keep
up with our
energy needs.
When you are hungry
a nerve sends a signal to your brain telling it that you need food.
Stimulus
Your brain sends a message to your stomach telling it to contract to signal that you are hungry.
Response

19. Homeostasis (Balance)
Stimulus
Response
Homeostasis (Balance)
Hunger
Eating
Hunger pains are gone

20. Stimulus Response Thirst -
A feeling of dryness in the mouth and throat.
Signals go from the mouth and throat
to the thirst center of the brain.
Response
The brain sends a signal to tell the body to drink water/fluids to maintain homeostasis.

21. Homeostasis (Balance)
Stimulus
Response
Homeostasis (Balance)
Thirst
Drinking water/
fluids
Body Fluid Balance

22. Muscle movement causes heat to build up (friction) and warm the body.
HOMEOSTASIS and
Body Temperature
Stimulus
Sweating helps maintain a stable
body temperature of about 98.6°F.
When we "heat up" we sweat.
The evaporation of sweat
returns the body to its
original temperature.
Response
Muscle movement causes heat to build up (friction) and warm the body.
Muscles shiver
to create heat.
Response
Stimulus

23. Homeostasis (Balance)
Stimulus
Response
Homeostasis (Balance)
Excess Body Heat
Low
Body
Temp.
Stable body temperature
Sweating
Stable body temperature
Shivering

24. Even more examples
Stimulus +
Response =
HOMEOSTASIS

25. Increase in heart rate and respiratory rate
HOMEOSTASIS
Stimulus
Response
Increased
Exercise
Increase in heart rate and respiratory rate

26. Stimulus Response Homeostasis (Balance)
Increased
Exercise
Increase
in heart rate and respiratory rate.
Normal O2 Levels in the blood

27. Fever or vomiting in animals allows them to maintain balance.
HOMEOSTASIS
Fever or vomiting in animals allows them to maintain balance.
Stimulus
Response
Food
Vomiting

28. Homeostasis (Balance)
Stimulus
Response
Homeostasis (Balance)
Spoiled
Food
Vomiting
Wellness

29. Fever or vomiting in animals allows them to maintain balance.
HOMEOSTASIS
Fever or vomiting in animals allows them to maintain balance.
Stimulus
Response
bacteria or
viruses
Fever

30. Homeostasis (Balance)
Stimulus
Response
Homeostasis (Balance)
Bacteria or Virus
Fever
Wellness

31. FIGHT or FLIGHT
If an organism feels threatened by an external stimulus, such as a predator, it responds by fighting or running away.

32. Homeostasis (Balance)
Stimulus
Response
Homeostasis (Balance)
Predator
Fight or
Flight
Threat
Eliminated

33. Homeostasis (Balance)
Stimulus
Response
Homeostasis (Balance)
1. Hunger
2. Thirst
3. Excess body heat
4. Low body temperature
5. Increased Exercise
6. Spoiled Food
7. Bacteria or Virus
8. Predator 9.
10.
11.

34. Use the three cards at your table to complete rows 9-11 on your chart.
Identify the stimulus, response, and balanced state (homeostasis) for each example.

35. Turgor pressure is restored
For Understanding
Stimulus
Response
Homeostasis
(Balance)
Excess water in the body
Excreted as urine.
Balanced water levels
Nightmare
Fight or Flight
Threat eliminated,
Sleep restored
Wilting plant
Roots take up water from the soil and pass it up through the rest of the plant.
Turgor pressure is restored

36. Notecard Knowledge 1. Answer to question #1 and your initials.
Number your notecard 1-4 and write the title.
Notecard Knowledge
1. Answer to question #1 and your initials.
Pass your card to the right when instructed.
2. Answer to question #2 and your initials.
Pass your card to the right when instructed.
3. Answer to question #3 and your initials.
Pass your card to the right when instructed.
4. Answer to question #4 and your initials.
Pass your card to the right when instructed.
Compare and Share Notecards

37. 1. Write one synonym for the word “stimulus”.
2. Which body system is responsible for regulating Homeostasis?
3. The Fight or Flight response is an example of an organism responding to an (internal or external) stimulus.
4. Write one synonym for the word “response”.

38. L1
1. Describe a situation where an organism responds to an external stimulus in order to maintain a state of balance, or homeostasis.
2. Describe a situation where an organism responds to an internal stimulus in order to maintain a state of balance, or homeostasis.

39. Directions: Fill in the blanks and complete the table below.
Organisms respond to changes in the environment in order to maintain balance. We call this balance (1)____________. The change in the environment is called a (2)________, and the reaction of the organism is called a (3)_______. Homeostasis is regulated by the (4)________ system.
Stimulus
Response
5. Spoiled Food
6. Bacteria or Virus
7. Hunger