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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, the root and stem respond differently to gravity due to the distribution of auxins, which are growth hormones in plants.
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Root Growth: The root exhibits positive geotropism, meaning it grows towards gravity. This is because there is a high concentration of auxins on the lower side of the root. The presence of auxins stimulates cell elongation and division on the lower side, while the upper side has a lower concentration of auxins, inhibiting growth. As a result, the root grows downwards, seeking moisture and nutrients from the soil.
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Stem Growth: In contrast, the stem demonstrates negative geotropism, growing away from gravity. The lower side of the stem has a higher concentration of auxins, promoting cell elongation on that side. The upper side, having a lower concentration, grows slower. Thus, the stem bends upwards as it grows away from the gravitational pull.
Step 2
Describe the role of the maculae in maintaining balance.
Answer
The maculae are critical structures in the inner ear that help maintain balance when a person tilts their head. When the head is tilted, the following process occurs:
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Stimulation: The movement of the head stimulates the sensory hair cells in the maculae located in the vestibule of the inner ear.
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Impulse Conversion: This mechanical stimulation is converted into electrical impulses.
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Transmission: The electrical impulses are transmitted through the auditory nerve to the brain.
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Interpretation: The brain interprets these impulses, providing information about the position of the head relative to gravity.
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Muscle Response: The brain sends signals to the muscles to make necessary adjustments to maintain balance.
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Balance Restoration: As a result, balance is restored, preventing the person from falling over.