PAGE 105 – QUESTIONS & ANSWERS
Q1. What is the difference between a reflex action and walking?
Answer:
| Reflex Action | Walking |
|---|---|
| Automatic, rapid, involuntary action | Slow, voluntary, controlled action |
| Does not involve thinking |
Requires thinking and decision |
| Controlled by spinal cord |
Controlled by brain (cerebellum) |
| Example: Pulling hand away from flame | Example: Walking, running |
Q2. What happens at the synapse between two neurons?
Answer:
At the synapse, the electrical impulse arriving at the end of one neuron triggers the release of chemical neurotransmitters into the gap.
These chemicals cross the synapse and start a new electrical impulse in the next neuron.
Q3. Which part of the brain maintains posture and equilibrium of the body?
Answer:
The cerebellum, located in the hindbrain, maintains balance, posture and precision of voluntary movements.
Q4. How do we detect the smell of an agarbatti (incense stick)?
Answer:
Odour molecules from agarbatti are detected by olfactory receptors in the nose.
These receptors send information to the forebrain, which interprets it as smell.
Q5. What is the role of the brain in reflex action?
Answer:
The reflex action is coordinated by the spinal cord, but signals also reach the brain, which interprets the situation and allows us to become aware of what happened after the action has already occurred.
Q1. What are plant hormones?
Answer:
Plant hormones are chemical substances produced in plants that regulate growth and responses to stimuli.
Example: Auxin, Cytokinin, Gibberellin, Abscisic acid
Q2. How is the movement of leaves of the sensitive plant different from the movement of a shoot towards light?
Answer:
| Sensitive plant movement | Shoot bending towards light |
|---|---|
| Very quick response | Slow response |
| Not dependent on growth | Depends on growth |
| Due to change in water content in cells |
Due to uneven auxin distribution |
Q3. Give an example of a plant hormone that promotes growth.
Answer:
Auxin – promotes cell elongation.
Q4. How do auxins promote the growth of a tendril around a support?
Answer:
When a tendril touches support, auxin collects on the opposite side, causing cells on that side to grow longer.
This unequal growth causes the tendril to curve around the support.
Q5. Design an experiment to demonstrate hydrotropism.
Answer:
Experiment:
-
Take a pot divided into two sections.
-
Fill both sides with soil.
-
Place seeds on both sides.
-
Pour water only on one side.
-
Cover pot for a few days.
Observation:
Roots bend towards the side containing water.
Conclusion:
Roots show positive hydrotropism.
PAGE 111 – QUESTIONS & ANSWERS
Q1. How does chemical coordination take place in animals?
Answer:
Animals use hormones, secreted by endocrine glands, which are released into the bloodstream and reach target organs, regulating growth, metabolism, reproduction, and emergency responses.
Q2. Why is the use of iodised salt advisable?
Answer:
Because iodine is necessary for the thyroid gland to produce thyroxin hormone.
Its deficiency causes goitre (swelling of the neck).
Q3. How does our body respond when adrenaline is secreted into the blood?
Answer:
Adrenaline prepares the body for fight or flight:
-
Faster heartbeat
-
Increased breathing rate
-
Increased blood flow to muscles
-
More oxygen supply
-
Energy release increases
Q4. Why are some patients of diabetes treated by giving injections of insulin?
Answer:
Diabetes occurs because the pancreas does not produce enough insulin, so blood sugar rises.
Injected insulin helps to control blood sugar levels.