Intext Questions Solved

Question 1 : What is the difference between a reflex action and walking?

Answer :

Reflex Action Walking
1. Reflex action is an involuntary action, i.e., it does not take place due to thought or thinking or will. 1. Walking is a voluntary action, i.e., it takes place due to thought or thinking or will.
2. It is sudden and fast taking place in response to an action. 2. It is not spontaneous . It is conscious effort.
3. It is controlled by spinal cord. 3. It is controlled by brain.
4. The connection between the neurons and spinal cord muscles forms the reflex arc for reflex action to take place. 4. There is no reflex arc for it.

Question 2 : What happens at the synapse between two neurons?

Answer : At the nerve endings of a neuron, the electrical signals release chemicals. These chemicals cross the gap/synapse and again start a similar electrical impulse in another dendrite of the another nerve cell. This is how the nerve impulse travels as electrical signals/charges along the nerve and passes to another nerve chemicals.

Question 3 : Which part of the brain maintains posture and equilibrium of the body?

Answer : Body posture and equilibrium (balancing) of the body is maintained by cerebellum.

Question 4 : How do we detect the smell of an agarbatti (incense stick)?

Answer : The fumes of agarbatti has chemicals of the fragrance. They are carried by air to the nose, from the nostrils they enter the mucosa of the nasal cavity where it is dissolved and picked up by neurons of the cavity. Then it is sent to sense receptors of the brain (olfactory receptors) the help us to smell the fragrance.

Question 5 : What is the role of the brain in reflex action?

Answer : Reflex action is an involuntary action, i.e., an action that does not need a thought/thinking or will to control it. It is spontaneous and controlled by spinal cord.

Therefore, brain does not play any role in it.

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Question 1 : What are plant hormones?

Answer : Plant hormones are chemical substances synthesised/produced by certain cells in the plant.

Question 2 : How is the movement of leaves of the sensitive plant different from the movement of a shoot towards light?

Answer :

Movement of leaves in sensitive plant Movement of a shoot towards light
1. It is because of change in the shape of cells due to the amount of water. 1. It is because of the elongation of cells due to the auxin (chemical).
2. It is in response to touch stimulus. 2. It is in response to light stimulus.
3. It is a movement without any growth. 3. It is a movement due to growth.
4. It is fast/quick response or movement of the plant. 4. It is very slow response or movement of the plant.

Question 3 : Given an example of a plant hormone that promotes growth.

Answer : Auxin.

Question 4 : How do auxins promote the growth of a tendril around the support?

Answer : The part of the tendril that is towards light will have less concentration of auxin than the part away from light. The shady part will show elongation of cells/growth of cells and increase in size. Therefore, it will grow in circle and coil the support.

Question 5 : Design an experiment to demonstrate hydrotropism.

Answer : Take few swollen gram seeds with germinated redicles. Place moist cotton at the base of the petri dish and above it keep a wire mesh. Now keep the seeds in petri dish over a wire mesh and observe it after a day or two. You will see that roots of seeds move through the wire mesh towards the moist cotton.

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Question 1 : How does chemical coordination take place in animals?

Answer : Chemical coordination takes place is animal by producing hormoes.

Question 2 : Why is the use of iodised salt advisable?

Answer : Iodine is required for the proper functioning of thyroid gland and for production of thyroxines hormone. Iodine is available in iodised salt. When when used in diet/food, supplies the required amount to the body for maintenance and thyroxine formation. The deficiency of iodine in diet leads to goitre – a disorder of thyroid gland. Also developed of brain is affected in developing babies. So, use of iodised salt is advisable.

Question 3 : How does our body respond when adrenalin is secreted into the blood?

Answer :

Question 4 : Why are some patients of diabetes treated by giving injections of insulin?

Answer : Patients of diabetes are given insulin injections to control the blood glucose level. Because their pancreas cannot/does not produce the required amount of insulin in the body.

Text Book Questions Solved

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

a) Insulin
b) Thyroxine
c) Oestrogen
d) Cytokinin

Answer : (d) Cytokinin.

Question 2 : The gap between two neurons is called a

a) Dendrite
b) Synapse
c) Axon
d) Impulse

Answer : (b) Synapse.

Question 3 : The brain in responsible for

a) Thinking
b) Regulating the heart beat
c) Balancing the body
d) All of the above

Answer : (d) All of the above.

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

Answer : The function of receptor is to receive the information from the environment through the neurons present in the body (receptor). When the receptors do not work properly or there is an obstruction in above activity then the sense shown/responded by the receptor will not take place. Such as during cold we do not smell/can not smell certain smells.

If such situations arise then we do not respond to the information given by the neurons.

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

Answer :

Neuron is the basic unit for information and conduction of impulses. It is the structural and functional unit of the nervous system also. It is responsible for carrying the information from the environment to receptors and from the spinal cord and brain to muscles/glands of the body. The information/messages are carried in the form of nerve impulses. It, therefore, connects the different parts of the body, sends and receives information, conducts reflexes, etc. It is just like electric circuit in a building.

Question 6 : How does phototropism occur in plants?

Answer : Phototropism is the movement of shoot towards the light source and roots away from the light source. In shoots it takes place due to high concentration of Auxin the plant hormone on the side away from light. This hormone promotes cell elongation on the shay side of the shoot this leads to growth of shoot and thus, bending towards the light source.

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

Answer : Reflex actions.

Question 8 : How does chemical coordination occur in plants?

Answer : Certain plant cells in plant synthesise chemical substances with promotors or inhibitors characteristics. These chemicals produced by cells at one place is distributed to other parts of the plants and cells of other regions respond/act according to these chemicals called plant hormones. This is the way how chemical coordination occur in plants.

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

Answer : Organism lives in a habitat (place) where many environmental factor/tiggers, such as light, heat, water, gravity, chemicals, etc., affect the organism. These factors may be harmful/dangerous to the organism and affect its survival. Therefore, the organism needs a system to ‘know’ about its environment and ‘protect’ itself or respond to it so that it can live better in that environment. So some organism such as animals have nervous system and chemical system and plants have chemical system to control and coordinate their body.

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

Answer :

Involuntary actions Reflex actions
1. Actions that take place by itself but are controlled by the brain are involuntary 1. Actions that take place of a sudden and are controlled by spinal cord
2. They do not have any circuit like reflex actions. 2. The have a circuit called reflex arc.
3. They take place at all times. 3. They take place only in presence of a stimulus.
4. We do not know always about its occurrence, e.g., heart beats. 4. We know about its occurrence, e.g., removal of the finger from a flame.

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

Answer :

Nervous control Hormonal control
1. Actions like reflex action are under the nervous control. 1. Control of blood glucose level in body is under the hormonal control.
2. Such actions are controlled mainly by a network/connections of neurons. 2. Such action is controlled.
3. Some actions are voluntary while others are involuntary. 3. All the actions are involuntary.
4. The cells/tissues/organs are connected with the neurons to CNS or peripheral nervous sytem. 4. The cells are supplied with chemicals via/through the blood.
5. The actions are fast. 5. The actions are slow.

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 :

Movement in sensitive plants Movement in leg
1. Movement in sensitive plant is in response to stimulus-touch 1. Movement in leg is in response to our will.
2. The movement takes place due to change in the shape of cells due to the amount of water. 2. Movement takes place due to contraction and relaxation of special proteins in muscle cells that changes the shape of cells.
3. It is not controlled by nervous as it is absent. 3. It is controlled by nervous system.