SAQ for Control and Cordination Class 10 Science NCERT
Important Questions1
(a) Write an activity to show phototropism and geotropism.
(b) What type of movement is shown by Mimosa plant leaves when touched with a finger?
Answer
(a) Activity to demonstrate phototropism and geotropism:
(i) Fill a conical flask with water.
(ii) Cover the neck of the flask with a wire mesh.
(iii) Keep two or three freshly germinated bean seeds on the wire mesh.
(iv) Take a cardboard box which is open from one side.
(v) Keep the flask in the box in such a manner that the open side of the box faces light coming from a window.
(vi) After two or three days, you will notice that the shoots bend towards light and roots away from light.
(vii) Now turn the flask so that the shoots are away from light and the roots towards light.
(viii) Leave it undisturbed in this condition for a few days.
(b) Folding up of the leaves of Mimosa plant is an example of nastic movements or seismonasty.
2
What is geotropism? Draw a labelled diagram of a potted plant showing positive geotropism and negative geotropism
OR
Define positive geotropism and negative geotropism. Give one example of each.
Answer
The upward growth of shoots and downward growth of roots in response to the pull of earth's gravity is called geotropism.
3
Answer
The growth movement in plants in response to force of gravity is known as geotropism. In geotropism, the roots of the plant always grow downwards while the shoots always grow upwards, away from the earth.4
Answer
Hydrotropism can be demonstrated with any germinating seedlings, which are allowed to grow on ground. The soil around the roots is separated by a polythene partition. The left side is kept moist and the right side dry. The radicle at first grows in a downward direction and after sometime the roots bend towards the moist soil. This is due to movement of the germinating roots towards water.5
(a) Which is (i) positively phototropic and (ii) negatively geotropic.
(b) Which is positively hydrotropic as well as positively geotropic?
(c) Which synthesises auxin ?
Answer
(a) (i) Positively phototrophic: Shoot
(ii) Negatively geotropic: Shoot
(b) Root
(c) Shoot tip
6
Answer
(i) Abscisic acid : Inhibits growth, wilting of leaves.
(ii) Gibberellins : Helps in the growth of stem.
(iii) Cytokinins : Promotes cell division.
Detailed Answer:
(i) Auxin : It promotes cell elongation and division, also helps in the formation of roots and seedless fruits.
(ii) Gibberellins : These are the hormones that help in the growth of the stem by elongation of internodes, it overcomes genetical dwarfism in plants.
(iii) Cytokinins : It promotes cell division and delay ageing in leaves. It reduces apical dominance and also stimulates the leaf expansion.
(iv) Abscisic acid : It is a growth-inhibiting hormone that reverses the growth-promoting effects of auxin and gibberellins. It causes dormancy of seeds, wilting of leaves, closing of stomata and loss of proteins and chlorophyll.
(v) Ethylene: It promotes transverse growth, also promotes senescence and abscission of leaves. It acts as an essential hormone for the artificial ripening of fruits.
7
Answer
Auxins produced in the shoot tip move downwards in the plant. These auxins cause cell elongation in the growing tissues. In the tendrils, auxins move away from the point of contact with the supporting object. More growth occurs on the side away from the support. As a result of unequal growth on the two sides, the tendril coils around the support.8
Answer
Plant hormone that promotes growth is Auxin.
Light falls on one side of the plant, auxins diffuse towards shady side of the shoot. Auxin stimulates the cells to grow longer on shady side. Plant appears to bend towards light.
9
(i) State the function of plant hormones. Name a plant hormone which is essential for cell division.
(ii) Name the hormone which is involved in phototropism. Explain its role.
Answer
(i) Plant hormones are the chemicals secreted by the plants which helps to co-ordinate growth, development and responses to the environment. Cytokinin
(ii) Auxin
When growing plant receives light, auxin is synthesized at the shoot tip and helps the cell to grow longer. When light comes from other side of the plant, auxin diffuses to shady side of the Shoot.
10
Answer
11
Answer
When growing plants detect light, a hormone called auxin, synthesized at the shoot tip helps the cell to grow longer. When light is coming from one side of the plant, auxin diffuses towards the shady side of the shoot. This concentration of Auxin stimulates the cells to grow longer on the side of shoot which is away from light. Thus, plant appears to bend towards light.12
Answer
Ethylene prevents wilting of leaves.
Two more examples are Auxins and Cytokinins.
Auxins are mainly concerned with cell enlargement. It also play role in phototropic and geotropic. Movements in plants.
Cytokinins play role in cell division.
13
Answer
14
Answer
Sensitivity to touch:
When tendril of a plant comes in contact with any object, the part of the tendril in contact with the object does not grow as rapidly as that part which is away from the object. This causes the tendril to circle around the object.
The plant get the support of the object for growing upward without falling.
15
Draw a neat diagram of human brain and label on it the following parts:
(i) Mid brain
(ii) Pituitary gland
(iii) Cerebellum
(iv) Cerebrum
Answer
(i) Labelled diagram of Human brain:
16
Answer
Reflex action is a sudden action in response to something in the environment. E.g. pulling out hand from the flame if accidently touched.
The path of the reflex action is as follows:
Receptors → sensory neuron → spinal cord → motor neuron → effector
17
Answer
(i) Collects information from the surroundings.
(ii) Controls and co-ordinates the movement of muscles
(iii) Helps to ecognize smell, taste, vision, hearing etc. with the help of sense organs.
18
Answer
Hormones should be secreted in precise quantities. The timing and amount of hormone released are regulated by feedback mechanism. For e-8, if the sugar level in blood rises, they are detected by the cells of the pancreas which respond by producing more insulin. As the blood sugar level, falls, insulin secretion is reduced.19
(a) Name one gustatory receptor and one olfactory receptor present in human beings.
(b) Write a and b in the given flow chart of neuron through which information travels and as an electrical impulse.
Answer
(a) Gustatory receptor - Tongue
Olfactory receptor - Nose
(b) (i) Cell body cyton
(ii) Axon
20
(a) Identify the glands that secrete:
(i) Insulin
(ii) Thyroxin.
(b) Explain with an example how the timing and amount of hormone secreted are regulated in the human body.
Answer
(a) (i) Insulin is secreted by pancreas.
(ii) Thyroxin is secreted by thyroid gland.
(b) The timing and amount of hormone released are regulated by feedback mechanism e. If the sugar level in blood rise, they are detected by the cells (Islets of Langerhans) of pancreas which respond by producing more insulin. As the blood sugar level falls, insulin secretion is reduced. 1
21
Name a hormone secreted by:
(i) Pancreas
(ii) Pituitary
(iii) Thyroid.
State one function of each of the hormones
Answer
(i) Pancreas secretes hormone insulin. It helps in regulating the blood sugar level
(ii) Pituitary secretes growth hormone. It regulates growth and development of the body.
(iii) Thyroid secretes thyroxine hormone. It regulates carbohydrates, protein and fat metabolism in the body so as to provide the best balance for growth.
22
(a) An old man is advised by his doctor to take less sugar in his diet. Name the disease from which the man is suffering. Mention the hormone due to imbalance of which he is suffering from this disease. Which endocrine gland secretes this hormone ?
(b) Name the endocrine gland which secretes growth hormone. What will be the effect of the following on a person:
(i) Deficiency of growth hormone.
(ii) Excess secretion of growth hormone.
Answer
(a) The man is suffering from Diabetes mellitus. Hormone is Insulin.
Endocrine gland that secretes insulin is pancreas.
(b) The endocrine gland which secretes growth hormone is pituitary gland.
(i) Deficiency of growth hormone causes dwarfism.
(ii) Excess secretion of growth hormone causes gigantism.
23
Answer
(a) The hormone which regulates carbohydrates, protein and fat metabolism in our body is thyroxine.
(b) Thyroxine hormone is secreted by thyroid gland.
(c) lodised salt in diet is important because it contains iodine, which is essential for the synthesis of thyroxine hormone by the thyroid gland. In case, iodine is deficient in our diet, there would be less production of thyroxin hormone and thus there is a possibility of suffering from goitre.
24
Answer
(i) Hormones are also known as chemical messengers as they act at a place different from the site of their manufacture
(ii) Their hyper and hypo secretion may cause disorder.
(iii) They help in control and co-ordination of the activities of living organisms.
25
(i) Name the hormone secreted by thyroid gland and state its function.
(ii) Why is it important for us to have iodised salt in our diet?
(iii) Name the disease caused due to deficiency of iodine and mention its main symptom.
Answer
(i) The hormone secreted by thyroid gland is thyroxin. It regulates carbohydrate, protein and fat metabolism in the body so as to provide the best balance for growth.
(ii) Iodine is necessary for the thyroid gland to make thyroxin hormone.
(iii) The disease caused due to deficiency of iodine is Goitre. Its main symptom is swollen neck.
26
Answer
The shape of muscles depends on ability to adapt to external forces. When placed under high demand, they generate great strength and power and maintain durability. Muscle is a soft tissue and their cells contain protein, filaments of actin and myosin that slide past one another, producing a contraction that changes both the length and shape of the cell.27
Pertaining to endocrine system, what will you interpret if :
(i) You observe swollen neck in people living in the hills.
(ii) Over secretion of Growth Hormone takes place during childhood.
(iii) Facial hair develops in boys aged 13.
Answer
(i) Less intake of lodine (in the diet)
(ii) Will lead to gigantism
(iii) Timely secretion of testosterone.
28
(a) How is brain protected from injury and shock?
(b) Name two main parts of hind brain and state the function of each.
Answer
(a) The brain is situated in the cavity of a bony box called skull. The brain is contained in a fluid filled balloon, which provides further shock absorption.
(b) Main parts of hind-brain are :
(i) Cerebellum : It is responsible for precision of voluntary actions and maintaining the posture and balance of the body.
(ii) Medulla oblongata : All involuntary actions, such as blood pressure, salivation, vomiting etc., are controlled by the medulla in the hind brain.
29
(a) Name the part of brain which controls:
(i) Voluntary action
(ii) Involuntary action.
(b) What is the significance of the peripheral nervous system? Name the components of this nervous system and distinguish between the origins of the two.
Answer
(a) (i) Voluntary action-Cerebellum,
(ii) Involuntary action - Medulla
(b) The communication between the central nervous system and the other parts of the body is facilitated by the peripheral nervous system. Carnial nerves and spinal nerves are its main components.
Carnial nerves arise from the brain; spinal nerves arise from the spinal cord.
30
16. In the given diagram of reflex arc:
(i) Name the parts labelled A, B, C, D and E.
(ii) Write the functions of B and E.
Answer
(i) A – Receptor
B – Sensory neuron/nerve
C – Relay neuron/ interneuron
D – Motor neuron/Nerve
E – Effector
(ii) B – Carried impulse from receptor to spinal cord
E – Responds to stimulus
31
(i) Identify the endocrine glands A, B, C, D, E and F in the given diagram.
(ii) List the function of parts D and F.
Answer
(i) A – Pituitary
B – Thyroid
C – Adrenal
D – Pancreas
E – Ovary
F – Testis.
(ii) Pancreas: Secrets insulin which controls amount of sugar in blood.
Testis: Secrets testosterone which controls sperm productions/secondary sexual character.
32
Mention one role of each of the following:
(i) Cerebellum
(ii) Fore-brain
(iii) Medulla
Answer
(i) Cerebellum: It is responsible for precision of voluntary actions and maintaining the posture and balance of the body.
(ii) Force-brain: Thinking
(iii) Medulla: Controls involuntary actions like blood pressure, salivation and vomiting.
33
Answer
Forebrain is the main thinking part of human brain.
Other Functions:
(i) Hearing, smell and sight
(ii) Storing information
(iii) Movement of voluntary muscles
(iv) Sensation of feeling hunger or satiety.
34
Answer
Adrenaline.
Two responses.
(i) It acts on heart due to which heart beats faster, resulting in the supply of more oxygen to our muscles.
(ii) The breathing rate increasing because of the contractions of the diaphragm and the rib muscles.
(iii) The blood to the digestive system and skin is reduced due to the contraction of muscles around small arteries in these organs.
35
Name the hormones by the following endocrine glands and specify one function of each:
(a) Thyroid
(b) Pituitary
(c) Pancreas
Answer
(a) Thyroxine, regulates carbohydrate, protein and fat metabolism/ controls metabolism for balance of body growth.
(b) Growth hormone, regulates growth and development of body (or any other correct answer)
(c) Insulin, regulates/ decreases blood sugar level.
OR
Glucagon, regulates/ increases blood sugar.
36
Answer
It is regulated by feedback mechanisms.
Example: Rise in sugar level in blood-insulin secreted by pancreas.
Fall in blood sugar level-insulin secretion is reduced.
37
Answer
(i) Adrenaline is carried to target organs/heart.
(ii) Heart beats get faster to supply more oxygen to muscles.
(iii) Blood supply to digestive system and skin is reduced.
(iv) Reach to connected Reach all the cells only of the body.
38
Answer
Brain and spinal cord are the parts of central nervous system. Brain is located inside a bony box, named as cranium and a fluid is present in this balloon, known as cerebrospinal fluid, which is a shock absorber.
Spinal cord is placed in a vertebral column and back bone protects it.