Matching exercise on stimulus and response concepts, including terms like stimulus, response, homeostasis, and tropisms.

Let’s go step by step to match each stimulus (left side) with the correct response or term (right side).

We’ll read each numbered item and find its best match from A–Q.

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1. Equal forces acting on an object in opposite directions.
→ This means no net force — things are balanced.
✔ Match: H. Balanced Forces

2. A push or pull exerted on an object
→ That’s the definition of force.
✔ Match: L. Force

3. An above normal body temperature that is part of the inflammatory response
→ That’s fever.
✔ Match: E. Fever

4. A change in an organism's surroundings that causes the organism to react.
→ This is an external trigger → external stimulus.
✔ Match: A. External stimulus

5. A tendency of growth or movement toward or away from the earth; the influence of gravity on growth
→ Gravity-related growth = geotropism.
✔ Match: G. Geotropism

6. The process by which an organism's internal environment is kept in equilibrium despite changes in the external environment.
→ That’s homeostasis.
✔ Match: J. Homeostasis

7. A change within an organism, such as hunger and thirst, that causes the organism to respond.
→ Internal trigger → internal stimulus.
✔ Match: B. Internal stimulus

8. A process in which a system is turned off by the condition it produces.
→ Like a thermostat turning off heat when room is warm → negative feedback.
✔ Match: O. Negative Feedback

9. The tendency of an organism to turn or move toward or away from light.
→ Light-directed growth/movement = phototropism.
✔ Match: F. Phototropism

10. An action or change in behavior that occurs as the result of a stimulus.
→ That’s the definition of a response.
✔ Match: D. Response

11. A young plant developing out of a plant embryo from a seed.
→ That’s a seedling.
✔ Match: M. Seedling

12. A change in an organism's surroundings that causes the organism to react
→ Same as #4? Wait — let’s check. Actually, this is also “stimulus” — but since #4 was matched to “external stimulus”, and this one doesn’t specify internal/external, maybe it’s just “Stimulus”. But look at Q: “Stimulus” — general term.
Wait — actually, #4 says “surroundings” → external. #12 also says “surroundings” → same thing? Hmm. Let’s recheck.

Actually, looking again:

#4: “A change in an organism's surroundings...” → external stimulus → A

#12: “A change in an organism's surroundings...” → same wording? Maybe typo? Or perhaps both refer to stimulus? But we have two options: A (External stimulus) and Q (Stimulus). Since #4 specifies “surroundings”, it’s clearly external. #12 also says “surroundings” — so should also be A? But we can’t use A twice.

Wait — let’s look at the list again. Maybe I misread.

Actually, #12 might be intended to be the general term “Stimulus” — but it says “surroundings”, which implies external. However, note that #7 is internal stimulus. So perhaps #12 is meant to be the general concept? But the wording is identical to #4.

This seems like a duplication error in the worksheet. But let’s think logically.

In biology, “stimulus” is any change that causes a reaction. “External stimulus” is a type of stimulus. Since #4 already took “External stimulus”, and #12 has the same description, perhaps it’s a mistake — but we must assign unique letters.

Wait — look at option Q: “Stimulus” — that’s the general term. And #12 says “a change... that causes the organism to react” — that’s the definition of stimulus. Even though it says “surroundings”, maybe it’s still acceptable for Q? But #4 is more specific.

Alternatively, perhaps #12 is meant to be “Stimulus” (Q), and #4 is “External stimulus” (A). That makes sense because #4 specifies “surroundings” (external), while #12 could be interpreted as general — even though it also says “surroundings”. Maybe it’s a wording overlap.

But let’s see other items.

Actually, let’s skip and come back.

13. The reaction of your body and mind to threatening, challenging, or disturbing events.
→ That’s stress.
✔ Match: I. Stress

14. The force of water against the cell wall or a plant cell.
→ Turgor pressure.
✔ Match: K. Turgor Pressure

15. Forces of different strengths acting in opposite direction.
→ Net force ≠ 0 → unbalanced force.
✔ Match: C. Unbalanced Force

16. The forceful expulsion of the contents of one's stomach through the mouth.
→ Vomiting.
✔ Match: N. Vomiting

17. Dehydration of plants to the point where the leaves lose their turgor and hang limply.
→ Wilting.
✔ Match: P. Wilting

Now back to #12: “A change in an organism's surroundings that causes the organism to react”

We already used A for #4. We have Q: “Stimulus” left. Since “stimulus” is the general term for any change causing a reaction, and #12 fits that definition (even if it mentions surroundings), and we need to use all letters, likely #12 → Q.

Also, note that #4 is specifically “external stimulus”, while #12 might be intended as the broader term — even though wording is similar. Perhaps it’s a trick to test if you know “stimulus” vs “external stimulus”.

So:

#4 → A (External stimulus)

#12 → Q (Stimulus) — accepting that “surroundings” might be slightly misleading, but in context, it’s the only logical choice left.

Also, check if any letter is unused.

List of matches so far:

1-H
2-L
3-E
4-A
5-G
6-J
7-B
8-O
9-F
10-D
11-M
12-Q ← assigning here
13-I
14-K
15-C
16-N
17-P

Used: A,B,C,D,E,F,G,H,I,J,K,L,M,N,O,P,Q — all 17 letters used. Perfect.

Double-check #12: If we put Q, then “Stimulus” is defined as “a change in surroundings...” — which is technically incomplete (since stimuli can be internal too), but in many textbooks, they start with external examples. Given the constraints, it’s acceptable.

Alternatively, maybe #12 was meant to be “Stimulus” and #4 “External stimulus” — yes, that’s standard.

So final mapping:

1. H
2. L
3. E
4. A
5. G
6. J
7. B
8. O
9. F
10. D
11. M
12. Q
13. I
14. K
15. C
16. N
17. P

All matched correctly.

Final Answer:
1-H, 2-L, 3-E, 4-A, 5-G, 6-J, 7-B, 8-O, 9-F, 10-D, 11-M, 12-Q, 13-I, 14-K, 15-C, 16-N, 17-P