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In text questions of page no. 119
Q. No. 1: What is the difference between a reflex action and walking?
Ans: A reflex action is voluntary action which is a rapid and automatic response to stimuli. While walking is a voluntary action which requires our thinking and in our control.
Q. No. 2: What happens at the synapse between two neurons?
Ans: A synapse is the gap between the two neurons. At synapse the electrical signals converted into chemicals that can easily cross over the gap and pass on to the next neurons where it again converted into electrical signals.
Q. No. 3: Which part of the brain maintains posture and equilibrium of the body?
Ans: Cerebellum, which is a part of hindbrain and is responsible for maintaining posture and equilibrium of the body.
Q. No. 4: How do we detect the smell of an agarbatti (incense stick)?
Ans: when the smell of the incense stick reaches to our nose then the olfactory receptors present in our nose detects it send this information in fore brain in the form of electrical signals. Fore brain interprets this information as the smell of incense stick where it is already stored.
Q. No. 5: What is the role of the brain in reflex action?
Ans: Reflex actions are sudden responses. It is involuntary action which does not involve thinking. For example, when we touch a hot object, we withdraw our hand immediately without thinking. 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 arcs are formed in the spinal cord and the information reaches the brain and the brain responses to it.
In text questions of page no. 122
Q. No. 1: What are plant hormones?
Ans: Plant hormones are the fluids which are secreted within the plant also known as phytohormones. Plant hormones regulate the growth and development of the plant. Examples of plant hormones are auxin, gibberellins etc.
Q. No. 2: How is the movement of leaves of the sensitive plant different from the movement of a shoot towards light?
Ans: The movements of the leaves of the sensitive plant are touch sensitive and independent of growth. While the movement of the shoot towards light is growth related and known as phototropism.
Q. No. 3: Give an example of a plant hormone that promotes growth.
Ans: Gibberellin is an example of plant hormone which promotes the growth of the plant.
Q. No. 4: How do auxins promote the growth of a tendril around a support?
Ans: Auxin is plant hormone which is synthesized at the tip of the shoot. It helps the cell grow longer. When a tendril comes in contact with a support, auxin stimulates faster growth of the cells on the opposite side thatâ€™s why the tendril forms a coil around the support.
Q. No. 5: Design an experiment to demonstrate hydrotropism.
Ans: Take a cubical transparent glass container and fill it with water. Now put some geminating seeds in it. After one or two days you will observe that the roots of all the geminating seeds will grow towards the water. This experiment proves that roots of germinating seed show the character of positive geotropism.
In text questions of page no. 125
Q. No. 1: How does chemical coordination take place in animals?
Ans: Chemical coordination takes place in animals with the help of hormones. Hormones are the chemical fluids that are secreted by the glands of the endocrine system. Hormones regulate the overall growth and development of the animals.
Q. No. 2: Why is the use of iodised salt advisable?
Ans: Iodine is needed by the thyroid gland for the production thyroxin hormone. This hormone regulates fat, protein and carbohydrate metabolism in our body. If this is in deficient quantity then the neck will swell up due to the enlargement of thyroid gland. This deficiency disease is known as goitre.
Therefore the iodised salt is advised.
Q. No. 3: How does our body respond when adrenaline is secreted into the blood?
Ans: When someone is in danger or in emergency then adrenal gland secrete adrenaline hormone. It is secreted directly into the blood and is transported to different parts of the body. It speeds up the heartbeat and hence supplies more oxygen to the muscles. This results in increasing breathing rate and blood pressure which enable them to fight with such urgent situation.
Q. No. 4: Why are some patients of diabetes treated by giving injections of insulin?
Ans: Insulin is a hormone secreted by pancreas that regulates the sugar level in the blood. When this hormone is not synthesised in proper amount then the sugar level in the blood rises and the persons suffer from diabetes.
This is the reason why diabetic patients are treated by giving injections of insulin.
Q. No. 1: Which of the following is a plant hormone?
Ans: (d) Cytokinin is a plant hormone.
Q. No. 2: The gap between two neurons is called a
Ans: (b) The gap between two neurons is known as synapse. Q. No. 3: The brain is responsible for
(b) regulating the heart beat.
(c) balancing the body.
(d) all of the above.
Ans: (d) all of the above. Brain is responsible for all of the above three functions.
Q. No. 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?
Ans: Receptors are present in our all parts of the body for example in skin, eye, nose tongue etc. They detect the signals and then send them to brain in the form of electrical signals. If they these receptors are damaged then it they will not detect the input which leads to the harm for our body in dangerous situation.
Q. No. 5: Draw the structure of a neuron and explain its function.
Ans: Neurons are nerve cells which are the functional units of the nervous system. The three main parts of a neuron are dendrite, cell body and axon.
Structure of neuron.
Functioning of its three parts.
Dendrite: It detect information and conducts the messages towards the cell body.
Cell body: It contains nucleus, mitochondria, and other cell organelles. It maintains the growth of the cell.
Axon: It conducts messages away from the cell body and pass to the next neuron.
Q. No. 6: How does phototropism occur in plants?
Ans: Environmental triggers such as light will change the directions that plant parts grow in. These directional, or tropic, movements can be either towards the stimulus, or away from it. So, in two different kinds of phototropic movement, shoots respond by bending towards light while roots respond by bending away from it.
Q. No. 7: Which signals will get disrupted in case of a spinal cord injury?
Ans: In case of the spinal cord injury, the signals coming from the nerves as well as the signals coming to the receptors will be disrupted. As both these signals meet in a bundle in spinal cord so there is any spinal cord injury then both these signals are disrupted.
Q. No. 8: How does chemical coordination occur in plants?
Ans: Chemical coordination in plants are occurred in plants with the help of fluids secreted in plants known as phytohormones or plant hormones. These hormones regulate the growth of the plants. For example auxin responsible for the growth of the plants and the Cytokinin helps in cell ision in the fast growing part of the plant such as plant hormones.
Q. No. 9: What is the need for a system of control and coordination in an organism?
Ans: There are various organs in an organism. These organs must be carefully controlled and coordinated for the survival of an organisms. In the body of an organism various fluids are secreted from the glands of the endocrine system. These hormones are responsible for the overall growth and development of an organism. All others daily decision that includes voluntary and involuntary action are controlled by central nervous system(CNS).
Q. No. 10: How are involuntary actions and reflex actions different from each other?
Ans: Involuntary action is the set of muscle movement which do not require thinking. But it is controlled by brain for example beating of heart beat.
While on the other hand, the reflex action is rapid and spontaneous action in response to any stimulus. For example closing of eyes immediately when bright light is focused.
|Nervous control||Hormonal Control|
|1||It is consist of nerveimpulses between PNS, CNS and Brain.||1||It consists ofendocrine system which secretes hormones directly into blood.|
|2||Here response time isvery short.||2||Here response time isvery long.|
|3||Nerve impulses are notspecific in their action.||3||Each hormone hasspecific actions.|
|4||The flow of information is rapid.||4||The flow of information is very slow.|
|Movement in sensitive plants||Movement in our legs|
|1||The movement in a sensitive a response to stimulus(touch)||1||Movement in our legs isa voluntary action.|
|2||No special tissue is there for the transfer of information||2||A complete system CNSand PNS is there for the information exchange.|
|3||Plant cells do not have specialised protein for movements.||3||Animal cells havespecialised protein which help muscles to contract.|
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