Chapter 7– Control and Coordination Solutions
Question - 1 : - What is the difference between a reflex action and walking?
Answer - 1 : -
Reflex action are the involuntary actions that occur in response to stimuli. They occur without involvement of conscious areas of brain. All the reflex actions are unconscious actions. Reflex action occurs brain and spinal cord of central nervous systems.
On the other hand voluntary actions are those which occur under the control of cerebellum of the brain Walking is learnt as we grow. Walking is controlled by brain as is used when required.
Question - 2 : - What happens at the synapse between two neurons?
Answer - 2 : - Between the synapse between two neurons electric signals are converted into chemicals that can easily cross over the gap and pass on the chemical messenger to next neuron where it is converted back to electrical signal.
Question - 3 : - Which part of the brain maintains posture and equilibrium of the body?
Answer - 3 : - Cerebellum which is a part of Hind brain is responsible for Controls the motor functioning hence it is the part reengaged in the maintenance of posture and equilibrium of the body.
Question - 4 : - How do we detect the smell of an agarbatti (incense stick)?
Answer - 4 : - Smell of an agarbatti is detected by Nose, olfactory receptors present in the nose sends electrical signal to the fore brain. Fore brain interprets this signal as the incense stick to be detected as smell.
Question - 5 : - What is the role of the brain in reflex action?
Answer - 5 : -
Reflex actions are formed instantaneously in response to the stimulus that has no time to think. For instance the sensory nerves that detect the heat are connected to the nerves that move the muscles of the hand. Such a connection of detecting the signal from the nerves (input) and responding to it quickly (output) is known as reflex arc.
Reflex action are generated in spinal cord and the information also reaches brain. This helps the brain to record this event and remember it for future use. Brain helps the person the person to get awareness of the stimulus and prevent himself from that situation again.
Question - 6 : - What are plant hormones?
Answer - 6 : - Plant hormones are the organic substances produces at certain sites of the plant and are translocated to other parts based on the requirement. Plant hormones help to coordinate growth, development and responses to the environment. Ex: Auxin’s Gibberlin’s, cytokines, abscisic acid and ethylene.
Question - 7 : - How is the movement of leaves of the sensitive plant different from the movement of a shoot towards light?
Answer - 7 : -
| Sl. no | Movement of leaves of the sensitive plant | Movement of a shoot towards light |
| 1 | It does not depend on the direction of stimulus applied. | Depends on the direction of stimulus applied. |
| 2 | Called as Nastic movement | Called as tropic movement |
| 3 | Touch is the stimulus | Light is the stimulus |
| 4 | Caused by the sudden loss of water from the swellings at the base of leaves | Caused by the unequal growth on the two sides of the shoot. |
| 5 | Not a growth movement | Growth movement |
| 6 | Occurs very fast | Occurs slowly |
Question - 8 : - Give an example of a plant hormone that promotes growth
Answer - 8 : -
Auxins and Gibberlins are the hormone responsible for the growth of plant.
Auxins are responsible for the cell elongation in shoot and also regulates growth.
Gibberlin is responsible for stem elongation and germination.
Question - 9 : - How do auxins promote the growth of a tendril around a support?
Answer - 9 : - Auxins are the plant hormones produces at the tip of a shoot and root. Auxins are present at the tip of tendrils. When tendrils are attached around any support their growth is slowed down as auxins are sensitive to touch. This make them move to the other side of the tip to get support this makes the other side grow faster than the side of tendril in contact with the support and the tendril bends towards the support.
Question - 10 : - Design an experiment to demonstrate hydrotropism.
Answer - 10 : -
To demonstrate hydrotropism in plants.
Procedure :
i. Plant a seedling in a vessel containing soil.
ii. Adjacent to the seedling put a porous pot containing water.
iii. Leave the set up for few days.
Observation :
iv. On examining the roots it is observed that the roots bend towards the source of water and do not grow straight.
result :
It confirms that plant shows hydrotropism as the roots bend towards the porous pot of water. As hydrotropism is a plant growth response in which the direction of growth is determined by a stimulus of gradient in water concentration.