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Both plants and humans respond to gravity - NSC Life Sciences - Question 4 - 2019 - Paper 1
Question 4
Both plants and humans respond to gravity. Explain why the root and the stem grow in different directions when a pot plant is placed horizontally on the ground, rec... show full transcript
Worked Solution & Example Answer:Both plants and humans respond to gravity - NSC Life Sciences - Question 4 - 2019 - Paper 1
Step 1
Explain why the root and the stem grow in different directions when a pot plant is placed horizontally
Answer
When a pot plant is placed horizontally, it experiences different gravitational responses due to the distribution of auxins, which are plant hormones.
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Root Growth Direction: The root grows downwards because:
- There is a high concentration of auxins on the lower side of the root. This concentration stimulates cell elongation and division.
- Conversely, the upper side has a low concentration of auxins, leading to reduced growth rates, causing the root to bend downwards towards gravity.
- Thus, the root exhibits positive geotropism, which is the growth towards gravitational pull.
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Stem Growth Direction: The stem grows upwards because:
- Similar to the roots, there is a high concentration of auxins on the lower side of the stem, promoting growth.
- The upper side of the stem has a lower concentration of auxins, inhibiting cell elongation and division, which results in faster growth on the lower side.
- This causes the stem to bend upwards, demonstrating negative geotropism, meaning it grows away from gravity.
Step 2
Also describe the role of the maculae in maintaining balance
Answer
The maculae play a crucial role in maintaining balance by detecting the position of the head in relation to gravity.
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Stimuli Processing: When the position of the head changes, the maculae are stimulated by the movement of the fluid within the inner ear.
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Impulses Transmission: This stimulus is converted into an impulse that travels through the auditory nerve.
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Interpretation: The impulses reach the brain, where they are interpreted to understand the position of the head.
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Balance Restoration: The cerebellum then sends impulses to the muscles to adjust body position, thus maintaining balance.
In summary, the maculae help a person tilt their head without falling by relaying crucial information about orientation and making necessary adjustments.