(a) (i) What is the effect of gravity on plant growth?
(ii) Describe an experiment to demonstrate the effect of gravity on the roots of plants.
(b) Explain how bitter taste is detected in humans.
(c) Copy and complete the table below on endocrine glands and their functions.
(ii) Describe an experiment to demonstrate the effect of gravity on the roots of plants.
(b) Explain how bitter taste is detected in humans.
(c) Copy and complete the table below on endocrine glands and their functions.
| S/N | Endocrine glands | Hormone produced | functions |
| 1 | Thyroid | ||
| 2 | Insulin | ||
| 3 | Development of secondary sexual characters of females |
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Correct Answer: Option n
Explanation:
(i) Effect of gravity on plant growth: The (main) root grows down in response to gravity/positively geotropic; the (main) stem/shoot/grows upwards away from gravity/negatively geotropic.
(ii) Experiment to demonstrate the effect of gravity on the roots of a plant: -
Select three germinating bean seedlings/seeds on a moist/damp sawdust/wet blotting paper
Pin/keep one seedling in a horizontal position
Place another seedling in a vertical position with the radicle pointing upwards
Place the third upwards vertical with the radicle pointing downwards, to serve as control
After few/2-3 days, it will be observed that the radicle of the seedling placed horizontally bends/ grows downwards
the radicle of seedling placed vertically bends/grows downwards
Indicating positive geotropism/ positive response to gravity.
The seedling placed vertically with radicle point downwards did not bend. (N.B. observation must correspond with the experimental procedure to score).
ALTERNATIVE to 1 (a)
(ii) Take a clinostat and two bean seedlings
Pin one seedling horizontally on damp/moist/wet/cotton wool/blotting paper attached to the cork of the clinostat
Pin the other seedling onto some damp/moist/wet cotton wool/blotting paper attached to the cotton tile
Start the motor of the clinostat; Observe the seedlings after 8 —10 hrs.
It will be observed that the radical of the seedling placed horizontally bends/grows down wards
Indicating/showing positive geotropism.
(b) Detection of bitter taste in humans
Taste buds are unevenly distributed on the surface of the tongue
Taste buds for detecting bitterness are at the back/end of the tongue
For a substance to be tasted it must be dissolved in a solution/saliva
When bitter substance is dissolved in saliva, sensory cells at end/back of the tongue are stimulated
Which pass impulses to the brain; Which interprets the taste as bitter.
(c) Hormones of endocrine glands and their functions
(i) Effect of gravity on plant growth: The (main) root grows down in response to gravity/positively geotropic; the (main) stem/shoot/grows upwards away from gravity/negatively geotropic.
(ii) Experiment to demonstrate the effect of gravity on the roots of a plant: -
Select three germinating bean seedlings/seeds on a moist/damp sawdust/wet blotting paper
Pin/keep one seedling in a horizontal position
Place another seedling in a vertical position with the radicle pointing upwards
Place the third upwards vertical with the radicle pointing downwards, to serve as control
After few/2-3 days, it will be observed that the radicle of the seedling placed horizontally bends/ grows downwards
the radicle of seedling placed vertically bends/grows downwards
Indicating positive geotropism/ positive response to gravity.
The seedling placed vertically with radicle point downwards did not bend. (N.B. observation must correspond with the experimental procedure to score).
ALTERNATIVE to 1 (a)
(ii) Take a clinostat and two bean seedlings
Pin one seedling horizontally on damp/moist/wet/cotton wool/blotting paper attached to the cork of the clinostat
Pin the other seedling onto some damp/moist/wet cotton wool/blotting paper attached to the cotton tile
Start the motor of the clinostat; Observe the seedlings after 8 —10 hrs.
It will be observed that the radical of the seedling placed horizontally bends/grows down wards
Indicating/showing positive geotropism.
(b) Detection of bitter taste in humans
Taste buds are unevenly distributed on the surface of the tongue
Taste buds for detecting bitterness are at the back/end of the tongue
For a substance to be tasted it must be dissolved in a solution/saliva
When bitter substance is dissolved in saliva, sensory cells at end/back of the tongue are stimulated
Which pass impulses to the brain; Which interprets the taste as bitter.
(c) Hormones of endocrine glands and their functions
| S/N | Endocrine glands | Hormone produced | Function |
| 1 | Thyroid | Thyroxin | influences growth/development; Regulates/controls rates of metabolism |
| 23 | PancreasOvary/ovaries | InsulinOestrogen | Control blood sugar level/causes liver to convert to convert glucose to glycogenDevelopment of secondary sexual characters of females |