Control and Coordination (NCERT Solution)

 Question 1: Which of the following is a plant hormone?

1. Insulin
2. Thyroxin
3. Oestrogen
4. Cytokinin
   Answer: (d) Ctyokinin

Question 2: The gap between two neurons is called a

1. Dendrite
2. Synapse
3. Axon
4. Impulse
   Answer: (b) Synapse

Question 3: The brain is responsible for

1. Thinking
2. Regulating the heart beat
3. Balancing the body
4. All of the above
   Answer: (d) All of the above

Question 4: What is the function of receptors in our body? Think of situations where receptors do not work properly. What problems are likely to arise?

Answer: Receptors provide information about the external environment so that the brain can instruct a related to organ to take necessary action. Receptors play an important role in our survival. Let us take the example of a person with hearing impairment. Certain ordinary task would be very difficult for that person. For example; while walking on the road, the person needs to hear the sound of vehicles moving near him. Without hearing those sounds, he would not be in a position to move safely on the road.

Question 5: Draw the structure of a neuron and explain its function.

Answer: Function of Neuron: Neuron transmits the nerve impulses.

Question 6: How does phototropism occur in plants?

Answer: Concentration of auxin changes in a particular plant part, in response to the direction of light. For example; in a stem, concentration of auxin increases in those parts which are away from light. This increases cell division in that part and thus the stem bends towards light. That is how phototropism occurs in plants.

Question 7: Which signals will get disrupted in case of a spinal cord injury?

Answer: The spinal nerves go to the organs which are below the head region. Moreover, the autonomous nervous system is also connected to the spinal cord. In case of spinal cord injury, communication between the spinal nerves and the brain would be disturbed. Similarly, the communication between the autonomous nervous system and brain would also be disturbed; in case of spinal cord injury.

Question 8: How does chemical coordination occur in plants?

Answer: Plant hormones play their roles in chemical coordination. Most of the plant hormones promote growth in certain plant parts, e.g. auxin, gibberellins and cytokinin. Abscissic acid is a plant hormone which inhibits growth. Shedding of leaves or ripe fruits is facilitated by abscissic acid.

Question 9: What is the need for a system of control and coordination in an organism?

Answer: A living being does not live in isolation. It has to constantly interact with its external environment and has to respond properly for its survival. For example; when a hungry lion spots a deer, the lion has to quickly make a move so that it can have its food. On the other hand, the deer needs to quickly make a move to run for its life.

Question 10: How are involuntary actions and reflex actions different from each other?

Answer: Involuntary actions are part of routine activities, while reflex actions are in response to a sudden danger. Moreover, involuntary actions happen in involuntary organs, while reflex action happens in a voluntary organ.

Question 11: Compare and contrast nervous and hormonal mechanisms for control and coordination in animals.

Answer: Nervous control is fast, while hormonal control is slow. Nervous control is facilitated by neurotransmitters, while hormonal control is facilitated by hormones.

Question 12: What is the difference between the manner in which movement takes place in a sensitive plant and the movement in our legs?

Answer: The movement in a sensitive plant is facilitated by chemical control, while the movement in our legs is facilitated by nervous control.

Control and Coordination(NCERT In Text Questions)

 Question 1: Design an experiment to demonstrate hydrotropism.

Answer: Following things are required for this experiment: Seeds of bean, a deep tray, sand, a porous flower pot

Procedure:

• The tray should be big enough to accommodate the porous pot.
• Fill the tray with sand and insert some seeds in it.
• Make a pit in the sand and insert the porous pot in it.
• Fill the porous pot with water.
• Leave the set up for about a week.

Observation: After a week when seeds are taken out, it is observed that roots grow in the direction of the porous pot. This shows hydrotropic movement in roots.

Question 2: What is the difference between a reflex action and walking?

Answer: Walking is a voluntary action and is part of routine activities. On the other hand, reflex action is involuntary and happens as a response to a sudden danger to a voluntary organ.

Question 3: What happens at the synapse between two neurons?

Answer: Transmission of nerve impulses between two neurons takes place at through the synapse. The axon terminal of a neuron releases specialized chemicals; called neurotransmitters. These chemicals travel through the synapse and reach the dendrites of the next neuron. The nerve impulses travel along with the neurotransmitters.

Question 4: Which part of the brain maintains posture and equilibrium of the body?

Answer: Cerebellum

Question 5: How do we detect the smell of an agarbatti (incense stick)?

Answer: The olfactory receptors; present in the nostrils; pick the smell. They send signals to the brain. The brain interprets those signals and we detect the smell of an incense stick.

Question 6: What is the role of the brain in reflex action?

Answer: Brain has no direct involvement in reflex action. Reflex action is mainly controlled at the level of spinal cord.

Question 7: What are plant hormones?

Answer: Plant hormones are special chemicals which regulate the growth of various plant parts.

Question 8: How is the movement of leaves of the sensitive plant different from the movement of a shoot towards light?

Answer: The movement of leaves of the sensitive plant is a nastic movement, i.e. it does not depend on the direction of the stimulus. On the other hand, the movement of a shoot towards light is a tropic movement, i.e. it depends on the direction from which light is coming.

Question 9: Give an example of a plant hormone that promotes growth.

Answer: Auxin

Question 10: How do auxins promote the growth of a tendril around a support?

Answer: Auxin increases in concentration in the part of the tendril which is away from the support. This results in increased cell division in that part. The part which is nearer to the support has lesser rate of cell division. As a result, the external part of the tendril grows more than the internal part and the tendril coils around the support.

Question 11: How does chemical coordination take place in animals?

Answer: Chemical coordination in animals takes place through hormones. There are several endocrine glands which secrete various kinds of hormones. These hormones regulate different functions in the body. For example; insulin is a hormone which regulates the blood sugar level.

Question 12: Why is the use of iodised salt advisable?

Answer: Iodine is an important constituent of the hormone thyroxine. Iodine deficiency leads to a disease called goiter. Iodised salt is advised to prevent chances of goiter.

Question 13: How does our body respond when adrenaline is secreted into the blood?

Answer: Adrenaline is also known as ‘fight or flight’ hormone. It prepares the body for emergency situations. Increased secretion of adrenaline in the blood increases the blood supply to limbs and to the facial area. It increases the heart rate and breathing rate so that more oxygen could be supplied to the limbs. Slight precipitation also occurs on the temple and in palms. All of this shows readiness for a fight or; if need be; a flight from the scene.

Question 14: Why are some patients of diabetes treated by giving injections of insulin?

Answer: Insulin plays an important role in sugar metabolism. In some patients of diabetes insulin secretion is reduced. Insulin injection is given to such patients to compensate for reduced insulin secretion.