Educational worksheet on plant responses to environmental stimuli, including phototropism and gravitropism.

Problem Analysis:

The task involves understanding plant responses to stimuli, specifically focusing on tropisms and nastic movements. The questions are designed to test knowledge of how plants respond to external stimuli such as light, gravity, and touch.

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Solution:

#### Question 1:
A plant's part responds to a given stimulus by bending toward it. This response is called:
- a. phototropism
- b. gravitropism
- c. nastic movement
- d. photoperiodism

Explanation:
- Phototropism: Plants bend toward a light source (e.g., stems growing toward sunlight).
- Gravitropism: Plants respond to gravity (e.g., roots grow downward, shoots grow upward).
- Nastic movement: Non-directional movement in response to stimuli like touch or temperature (e.g., Venus flytrap closing its trap).
- Photoperiodism: Response to the length of day and night (e.g., flowering in plants).

Since the question specifies that the plant bends toward the stimulus, the correct answer is:
- Answer: a. phototropism

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#### Question 2:
The functioning of a hormone is to change the growth rate of a cell. This hormone is called:
- a. auxin
- b. gibberellin
- c. cytokinin
- d. abscisic acid

Explanation:
- Auxin: Primarily responsible for promoting cell elongation and bending in response to stimuli (e.g., phototropism and gravitropism).
- Gibberellin: Promotes stem elongation and seed germination.
- Cytokinin: Stimulates cell division and delays aging.
- Abscisic acid: Inhibits growth and promotes dormancy.

Since the question asks about a hormone that changes the growth rate of a cell, the correct answer is:
- Answer: a. auxin

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#### Question 3:
Any change in the environment that causes a response in an organism is called:
- a. stimulus
- b. tropism
- c. nastic movement
- d. adaptation

Explanation:
- Stimulus: Any environmental factor that triggers a response in an organism (e.g., light, touch, gravity).
- Tropism: Directional growth response to a specific stimulus (e.g., phototropism, gravitropism).
- Nastic movement: Non-directional movement in response to stimuli (e.g., Venus flytrap).
- Adaptation: Long-term evolutionary change in an organism to better suit its environment.

Since the question asks for any change in the environment that causes a response, the correct answer is:
- Answer: a. stimulus

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#### Question 4:
In Figure 1, the root grows downward because the effect of the stimulus depends on:
- a. the type of stimulus
- b. the part of the plant
- c. the intensity of the stimulus
- d. the duration of the stimulus

Explanation:
- Figure 1 shows a root growing downward, which is an example of gravitropism. Roots grow downward due to the influence of gravity.
- The direction of growth (downward) depends on the part of the plant (roots vs. shoots). Roots grow downward, while shoots grow upward in response to gravity.

Thus, the correct answer is:
- Answer: b. the part of the plant

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#### Question 5:
Which of the following statements is true regarding plant growth?
- a. Auxin is produced only in the shoot tips.
- b. Auxin can generate both positive and negative tropisms.
- c. Auxin is transported from the shoot tips to the roots.
- d. Auxin is involved in wound healing.

Explanation:
- Option a: Auxin is not produced only in shoot tips; it is also produced in other parts of the plant, such as developing fruits and young leaves.
- Option b: Auxin can indeed generate both positive tropisms (growth toward the stimulus, e.g., phototropism in stems) and negative tropisms (growth away from the stimulus, e.g., gravitropism in roots).
- Option c: Auxin is transported from shoot tips to other parts of the plant, including roots, but this is not the best choice for the question.
- Option d: While auxin is involved in some aspects of wound healing, it is not the primary function mentioned in the options.

Thus, the correct answer is:
- Answer: b. Auxin can generate both positive and negative tropisms.

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#### Question 6:
Because of the effect of auxin on cell wall growth, plant stems grow:
- a. longer
- b. thicker
- c. shorter
- d. wider

Explanation:
- Auxin promotes cell elongation, which leads to increased length in stems. It does not primarily affect the thickness or width of stems.

Thus, the correct answer is:
- Answer: a. longer

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#### Question 7:
The Venus flytrap showing its trap after being touched is an example of:
- a. negative phototropism
- b. positive gravitropism
- c. nastic movement
- d. positive geotropic response

Explanation:
- Negative phototropism: Growth away from light (not applicable here).
- Positive gravitropism: Growth toward gravity (e.g., roots growing downward).
- Nastic movement: Non-directional movement in response to stimuli, such as touch (e.g., Venus flytrap closing its trap).
- Positive geotropic response: Growth toward gravity (same as positive gravitropism).

Since the Venus flytrap closes its trap in response to touch, this is an example of nastic movement.

Thus, the correct answer is:
- Answer: c. nastic movement

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Final Answers:

1. a. phototropism
2. a. auxin
3. a. stimulus
4. b. the part of the plant
5. b. Auxin can generate both positive and negative tropisms.
6. a. longer
7. c. nastic movement

Boxed Final Answer:
\[
\boxed{a, a, a, b, b, a, c}
\]