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SOLUTION OF CH-7 CONTROL AND COORDINATION

Solutions of Ch - 7 Control and Coordination 

I. Very short answer type questions: 

1. What is the function of receptors?

Ans. The functions of receptors are to detect test and smell and these receptors are usually located in our sense organs, such as the inner ear, the nose, the tongue, and so on.

2. Write the correct sequence of electric impulse travels in a neuron.

Ans.  The correct sequence of electric impulse travels in a neuron is - 
Dendrite →Cell body → Axon → Nerve ending → Next neuron. 

3. Where is the conversion of an electric signal to a chemical signal in a neuron occurs?

Ans. In the dendrite, the conversion of an electric signal to a chemical signal in a neuron occurs and creates electric impulse.

 4. Which element is necessary for the synthesis of thyroxin hormone?

Ans. Iodine is necessary for the synthesis of thyroxin hormone.

5. Which part of the brain controls voluntary actions?

Ans. the cerebellum which is a part of the hind-brain is responsible for the precision of voluntary actions like walking in a straight line, riding a bicycle, picking up a pencil.

6. Which gland secrets the hormone insulin?

Ans. Insulin is produced by the pancreas and helps in regulating blood sugar levels. 

7. All information for our environment is detected by the specialized tip of some nerve cells. Mention the name given to search tips and also mention where are they located?

Ans. The specialized tip is called the dendritic tip of a nerve cell and is usually located in our sense organs, such as the inner ear, the nose, the tongue, and so on.  

8. What is the function of the tendril in the pea plant?

Ans. Tendrils provide support to the plants and help to climb.

9. Define chemotropism.

Ans. A chemotropism is a form of tropism in which the plant’s organism grows in response to a chemical stimulus and one example of chemotropism is the growth of pollen tubes towards ovules.

10. Define phototropism.

Ans. Phototropism is a form of tropism in which the plant’s organism grows in response to a light stimulus and one example of phototropism is the growth of the movement of sunflowers in response to day or night.

11. What is the reason for dwarfism?

Ans. Growth hormone is one of the hormones secreted by the pituitary regulates growth and development of the body and if there is a deficiency of this hormone in childhood, it leads to dwarfism.

12. Write three paired glands and one unpaired gland.

Ans. Pair gland- Adrenaline gland, Testis in male, Ovary in the female.
Unpaired gland -  Pituitary gland, thyroid gland, pineal gland.

13. What is the junction between two neurons?

Ans. Neuromuscular junction.

14. Which system control and regulate the life processes in human?

Ans. The nervous and endocrine systems control and regulate the life processes in humans.

15. Which hormone increases fertility in males?

Ans. Testosterone hormone increases fertility in males.

16. Which chemical substance is responsible for the formation of abscission which disconnects the living tissue of leaf from the other parts?

Ans. Abscisic acid is responsible for the formation of abscission which disconnects the living tissue of leaf from the other parts.

17. Name the sensory receptors found in the nose and on the tongue?

Ans. Olfactory receptors detect smell which is found in the nose while gustatory receptors detect taste and present in the tongue.

18. Name the part of the brain which controls the posture and balance of the body. 

Ans. The cerebellum of the brain is responsible for the precision of voluntary actions and maintaining the posture and balance of the body.

19. Name the two components of the central nervous system in humans.

Ans. The two components of the central nervous system in humans are the brain and spinal cord.

20. Mention that part of the body where gustatory and olfactory receptors are located.

Ans. Gustatory - Tongue
Olfactory - Nose

21. How do the shoot and root of plant response to the pull of Earth's gravity?

Ans. Upward (negative geotropism) and downward (positive geotropism) growth of shoots and roots, respectively, in response to the pull of earth or gravity, that is geotropism. 

22. State the main functions of abscisic acid in Plants.

Ans. Abscisic acid in Plants helps in the wilting of leaves.

23. What is synapse?

Ans. The Synapse is the point of connection between two neurons or between a neuron and a muscle or gland through which electric impulse is delivered.

24. A boy runs on seeing a stray dog, his breathing becomes very fast and blood pressure also increases. Name the hormones found to be high in his blood and the gland which produces it. 

Ans. The hormone adrenaline is secreted from the adrenal glands. 

25. What is meant by tropic movement?

Ans. Environmental triggers such as light, or gravity will change the directions that plant parts grow in. These directional movements are called tropic movement, it can be either towards the stimulus or away from it.  

27. Name the part of the neuron where information is acquired.

Ans. Information, acquired at the end of the dendritic tip of a nerve cell that sets off a chemical reaction that creates an electrical impulse. 

28. Name the part of the neuron through which the information travels as an electric impulse.

Ans.  Axon is the part of the neuron through which the information travels as an electric impulse.

  
29. Name the mechanism by which the amount of hormones in the blood is regulated.

Ans. The amount of hormone released is regulated by feedback mechanisms.

30. Name two tissues that provide control and coordination in animals.

Ans. Two tissues that provide control and coordination in animals are nervous and muscular tissues.

31. Name the disease by which a person is likely to suffer due to the deficiency of Iodine and Insulin.

Ans. Goiter is the disease by which a person is likely to suffer due to the deficiency of Iodine and the symptom is a swollen neck.

32. Define phototropism.

Ans. The growth of a plant or other organism in response to light, either towards the source of light ( positive phototropism ) or away from it ( negative phototropism ) is called phototropism.

33. Name the largest cell present in the human body.

Ans. Nerve cell the largest cell present in the human body.

35. How does our body maintain blood sugar levels?

Ans. Insulin is a hormone that is produced by the pancreas and helps in regulating blood sugar levels. 

II. Short answer type question: 

1. Name the hormones responsible for the regulation of
 (i) Metabolism of carbohydrates fats and proteins. 
(ii) Balance of calcium and phosphate 
(iii) Blood pressure 
(iv) Water and electrolyte balance.
Ans. (i) Thyroxin hormone (produced by the thyroid gland).
(ii) The parathyroid hormone (produced by Parathyroid glands present in the neck behind the thyroid gland).
(iii) Aldosterone hormone (produced by adrenal glands).
(iv) Antidiuretic Hormone (released from the pituitary gland).

2. When a person is suffering from severe cold, he or she cannot differentiate the smell of perfume. Why?
Ans. The nose contains olfactory receptors that detect the smell. When a person is suffering from severe cold, the nose gets blocked so olfactory receptors cant detects any smell.

3. What will happen if the intake of iodine in our diet is low?
Ans. If the intake of iodine in our diet is low, there is a possibility that we might suffer from goiter. One of the symptoms of this disease is a swollen neck. 

4. What is tropic movement? Explain with an example.
Ans. Environmental triggers such as light, or gravity will change the directions that plant parts grow in. These directional movements are called tropic movement, it can be either towards the stimulus or away from it. 
Example - The roots of a plant always grow downwards while the shoots usually grow upwards and away from the earth and this movement in response to gravity, which is geotropism.   

5. What is reflex action ? Give two examples.
Ans.  In some situations where we are responding with some action to changes in our environment without thinking about it or feeling in control of our reaction. This reaction is known as a reflex reaction.
Examples - (i) I pulled my hand back from the flame reflexly, 
(ii) I was so hungry my mouth started watering reflexly.

6. Explain the cause of shoots of the plant bending towards the light.
Ans. Phototropism is the cause of shoots of the plant bending towards the light which is a kind of phototropic movement in which plant parts grow towards the light. 

7. What are the nastic and curvature movements? Give one example of each.
Ans. Nastic Movements - It is non-directional movements that show response towards stimuli like light, temperature. The direction of nastic movements is independent of the direction of the stimulus.
Example - Opening and closing of flowers.

Curvature Movements - This movement includes bending or curving of a plant in response to any stimuli.
Example - Curving of the stem tip (tendril) towards the light and curving of roots away from light. 

8. Write the name and function of any two parts of the hind-brain.
Ans. Cerebellum and medulla are the two parts of the hind-brain.
Functions: 
(i) Cerebellum - It controls voluntary actions like walking in a straight line, riding a bicycle, picking up a pencil and maintaining the posture and balance of the body.
(ii) Medulla -  It controls involuntary actions like blood pressure, salivation, and vomiting.  

9. Explain with the help of an example of how the timing and amount of hormones released regulated?
Ans. The timing and the amount of hormone released are regulated by feedback mechanisms. 
For example - If the sugar levels in the blood rise, 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. 

10. Nervous and hormonal systems together perform the function of control and coordination in human beings. Justify the statement.
Ans. Control and coordination are the functions of the nervous system and hormones in our bodies. 
The nervous system uses electrical impulses to transmit messages gets information from our sense organs and acts through our muscles.
Hormones produced by the hormonal system, in one part of an organism move to another part to achieve the desired effect. A feedback mechanism regulates the action of the hormone.

11. (i) Draw a well-labeled diagram of the human brain. 

(ii) Which is the main thinking part of the brain? 
Ans. (i) diagram
(ii) The brain has three major parts, namely the fore-brain, mid-brain, and hind-brain. Fore-brain is the main thinking part of the brain and it has regions that receive sensory impulses from various receptors.

12. Identify the gland that secretes (i) Insulin & (ii) Thyroxin. 
Ans. (i) Pancrease secrets insulin hormone and helps in regulating blood sugar levels.
(ii) Thyroid gland secrets thyroxin.

13. Name the property that causes the tendrils to circle around the object. Explain how it happens and how the plan is benefited by it. 
Ans. Thigmotropism is the causes the tendrils to circle around the objects.
Some plants like the pea plant climb up other plants or fences by means of tendrils. These tendrils are sensitive to touch. When they come in contact with any support, the part of the tendril in contact with the object does not grow as rapidly as the part of the tendril away from the object. This causes the tendril to circle around the object and thus cling to it.

14. How does chemical coordination take place in animals?

Ans. Hormones help in chemical coordination in animals which is secreted by the endocrine gland. It is a chemical messenger that regulates the physiological processes in living organisms. The regulation of physiological processes, and control and coordination by hormones comes under the endocrine system.

15. How is the brain protected from injury and Shock? Name two main parts of the hindbrain and state the function of each.
Ans. The body is designed so that the brain sits inside a bony box. Inside the box, the brain is contained in a fluid-filled balloon which provides further shock absorption.
cerebellum and medulla are the two main parts of the hind-brain.
The cerebellum controls voluntary action and medulla controls involuntary action. 

16. Name a hormone secreted by the :
(i) Pancreas (ii) Pituitary (iii) Thyroid. 

State one function of each of the hormones.
Ans. (i)  Insulin secreted by the pancreas -Insulin helps in regulating blood sugar levels.  

(ii) Growth hormone secreted by the pituitary gland - Regulates growth and development of the body  

(iii) Thyroxin secreted by the thyroid gland - Provide the best balance for growth.

17. Define reflex action. Give one example. Show with the help of a flow diagram of the path of the reflex action.
Ans. Reflex action is a quick response (without thinking about it, or without feeling in control of our reactions) in situations where the organism does not have enough time to think.

18. How do auxins help in bending of the stem towards the light? Explain.
Ans.  Auxin is a plant growth hormone. When growing plants detect light,  auxin, synthesised at the shoot tip, helps the cells 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 the shoot which is away from light. Thus, the plant appears to bend towards the light.

19. How do auxins promote the growth of a tendril around a support? Describe in brief.
Ans. Auxin is a plant growth hormone that 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 that's why the

tendril forms a coil around the support.

20. In the given diagram of reflex arc (i) Name the parts labeled A B C D  and G (ii) Write the functions of C & B. 

 Ans. (i) A - Receptor

B - effector

C- sensory nerve

G - Motor nerve

D - Relay neuron

(ii) C - carries impulse from receptor to spinal cord

B - Responds to stimulus.

21. Name the hormones that are secreted by our body to deal with scary situations. List any two responses shown by our body when these hormones are secreted into the blood.
Ans. Adrenaline hormones that are secreted from the adrenal glands to deal with scary situations.
i. It acts on the heart due to which the heart beats faster, resulting in the supply of more oxygen to our muscles. 
ii. The blood to the digestive system and skin is reduced due to the contraction of muscles around small arteries in these organs.

22. Electrical impulses are an excellent mean of quick transfer of information in animals but there is a limitation to the use of electrical impulses. A list such as limitations. State the other means of communication used by most multicellular organisms between the cells.
Ans.  Firstly, they will reach only those cells that are connected by nervous tissue.
 Secondly, once an electrical impulse is generated in a cell and transmitted, the cell will take some time to reset its mechanisms before it can generate and transmit a new impulse.  
It is thus no the wonder that most multicellular organisms use another means of communication between cells, namely, chemical communication.

23. Name the plant hormones responsible for the following:

(i) Elongation of cells (ii) Growth of steam(iii) Promotion of cell division(iv) Falling of sensors and leaves.
Ans. (i) Auxin 
(ii)  Gibberellins 
(iii) Cytokinins 
(iv) Abscisic acid.

24. While watering a rose plant, a thorn pricked Rita's hand. How would she respond to this situation? Provide the term for such type of response.
Ans. When a thorn pricked Rita's hand, she will suddenly move away her hand. This type of response is known as a reflex action. 

25. State the role of the brain in a reflex action.
Ans. Reflex action is a quick response (without thinking about it, or without feeling in control of our reactions) in situations where the organism does not have enough time to think. Reflex arcs are formed in the spinal cord, although the information inputs also reach the brain. 

26. What happens at the synapse between two neurons?

Ans.  At the end of the axon, the electrical impulse sets off the release of some chemicals and these chemicals cross the synapse and start an electrical impulse in a dendrite of the next neuron.

27. The gland secretes a particular hormone. The deficiency of this hormone in the body causes a particular disease in which the blood sugar level rises. 

(i) Name the gland and the hormone secreted by it. 

(ii) Mention the role played by this hormone. 

(iii) Name the disease caused due to deficiency of this hormone.

Ans. (i) The gland is the pancreas that secrets insulin.

(ii) Insulin helps in regulating blood sugar levels.

(iii) Diabetes is the disease caused due to deficiency of this hormone insulin.

28. Brain and spinal cord are two vital organs of our body. How is our body designs to protect them?

Ans. The body is designed so that the brain sits inside a bony box. Inside the box, the brain is contained in a fluid-filled balloon which provides further shock absorption. 

If we run our hand down the middle of our back, we will feel a hard, bumpy structure. This is the vertebral column or backbone which protects the spinal cord.

29. (i) Name the part of the neuron where information is acquired.

(ii) Through which information travels as an electrical impulse. 

Ans. (i) Information is acquired at the end of the dendritic tip of a nerve cell.

(ii) Information travels through axon as an electrical impulse. 

III. Long answer type questions:

1. Mention one function of each of these hormones: Thyroxine, Insulin, Adrenaline, Growth hormones and Testosterone.
Ans. Thyroxin -  regulates carbohydrate, protein, and fat metabolism in the body so as to provide the best balance for growth.

Insulin -  helps in regulating blood sugar levels.

Adrenaline - helps in increasing the heart rate, increasing blood pressure,  enlarging the pupil in the eye, diverts the blood to our skeletal muscles redistributing blood to the muscles and altering the body's metabolism, to maximise blood glucose levels.

 Growth hormone - regulates growth and development of the body.

Testosterone - helps in the development of male reproductive tissues such as testes and prostate.

2. What are the major parts of the brain? Mention the function of different parts.

Ans. The brain has three major parts or regions, namely the fore-brain, mid-brain, and hind-brain. 

Fore-brain is the main thinking part of the brain. It receives sensory impulses from various receptors. Forebrain controls body temperature, blood sugar, hunger, sensory signals. It also controls motor which controls the movement of voluntary muscles.

Mid-brain controls involuntary actions like mouth started watering reflexly, hearts beat without our thinking about it, change in the size of the pupil, and the thought out actions such as moving a chair, are controlled by the mid-brain.

Hind-brain controls involuntary actions including blood pressure, salivation, and vomiting, think about activities like walking in a straight line, riding a bicycle, picking up a pencil. 

3. I. Answer the following :

(i) Name the endocrine glands associated with the brain.
(ii) Which gland secretes digestive enzymes as well as hormones?
(iii) Name the endocrine gland associated with Kidneys?
(iv) Which endocrine gland is represented in males but not in a female?

II. List in tabular form the three differences in the movement of leaves of a touch-me-not plant when touched and movement of a tendril towards support.

Ans. I. (i) The pituitary gland and pineal gland are associated with the brain.

(ii) The pancreas secretes digestive enzymes as well as hormones.

(iii) The adrenal gland associated with Kidneys.

(iv) The testis gland is represented in males but not in a female.

II. (i) Movement in a touch-me-not plant is a non-directional movement whereas in a tendril movement is directional movement.

(ii) Movement in touch-me-not plant mostly exhibited by the leaf and flower petals whereas mostly stem and branch of plant sow movent like movent in a tendril.

(iii) The direction of movement in touch-me-not does not depend upon the direction of the stimulus whereas the direction of movement in a tendril is depended upon stimulus. 

4. i. Name that hormone released by the thyroid gland. Also, write the function of this hormone. Give one of its symptoms.

I. A florist sprinkled a plant hormone to prevent wilting of leaves. Name the hormones he must have used. 

Ans. I. Thyroxin hormone released by the thyroid gland. 

Thyroxin regulates carbohydrate, protein, and fat metabolism in the body so as to provide the best balance for growth.

Iodine is essential for the synthesis of thyroxin. In the case of iodine is deficient in our diet, there is a possibility that we might suffer from goiter. One of the symptoms of this disease is a swollen neck. 

II. A florist sprinkled a plant hormone called ethylene which helps in wilting of leaves and ripening of fruits. It also stimulates shoot and root growth.

5. Name the main thinking part of the human brain. List four major functions of this part.

Ans. Fore-brain is the main thinking part of the brain. 

i. It receives sensory impulses from various receptors. 

ii. Separate areas of the fore-brain are specialised for hearing, smell, sight and so on. 

iii. In this part of the brain sensory information is interpreted by putting it together with information from other receptors as well as with information that is already stored in the brain.

iv. It controls body temperature, reproductive functions, eating, sleeping, and the display of emotions.

6. Name the plant hormones that promote growth. How do these hormones bring about phototropism in the shoot of a plant?

Ans. Two plant hormones are gibberellins and cytokinins that promote growth. 

Gibberellins help in the growth of the stem and cytokinins promote cell division.

When growing plants detect light, a hormone called auxin, synthesized at the shoot tip, helps the cells 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 the shoot which is away from light. Thus, the plant appears to bend towards the light.

7. What constituents the central and Peripheral nervous system? How are the components of the central nervous system protected?

Ans. The brain and the spinal cord constitute the central nervous system. They receive information from all parts of the body and integrate it.

The communication between the central nervous system and the other parts of the body is facilitated by the peripheral nervous system consisting of cranial nerves arising from the brain and spinal nerves arising from the spinal cord. The brain thus allows us to think and take actions based on that thinking. 

Brain protected by the bony box. Inside the box, the brain is contained in a fluid-filled balloon which provides further shock absorption and the vertebral column or backbone which protects the spinal cord.

8. What is the function of the mid-brain? Name the three different parts of the hindbrain and give one function of each.

Ans.  Our mouth waters when we see the food we like without our meaning to, our hearts beat without our thinking about it, change in the size of the pupil, and the thought out actions such as moving a chair, there is another set of muscle movements over which we do not have any thinking control. Many of these involuntary actions are controlled by the mid-brain. 

Three parts of the hindbrain are medulla oblongata, pons and cerebellum.

Functions:

Involuntary actions including blood pressure, salivation and vomiting are controlled by the medulla.

Activities like walking in a straight line, riding a bicycle, picking up a pencil. These are possible due to the cerebellum. It is also responsible for the precision of voluntary actions and maintaining the posture and balance of the body

Pons regulating the breathing rhythm, sleep, respiration, swallowing, bladder control, and hearing, etc.

9. I. Name two hormones secreted by the pancreas. Write one function of each hormone. 

II. How does our body respond when adrenaline is secreted into the blood?  

Write an example to explain the feedback mechanism for the regulation of hormone secretion.

Ans. I. Insulin and gastrin are the two hormones secreted by the pancreas.

 Insulin helps in regulating blood sugar levels. If it is not secreted in proper amounts, the sugar level in the blood rises causing disease like diabetes.

II.  Adrenaline is secreted directly into the blood from the adrenal glands and carried to different parts of the body. The target organs or the specific tissues on which it acts include the heart. As a result, the heart beats faster, resulting in the supply of more oxygen to our muscles. The blood to the digestive system and skin is reduced due to the contraction of muscles around small arteries in these organs. This diverts the blood to our skeletal muscles. The breathing rate also increases because of the contractions of the diaphragm and the rib muscles. All these responses together enable the animal body to be ready to deal with the situation.

Example of feedback mechanism for the regulation of hormone secretion.: If the sugar levels in the blood rise, 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.

10. (i) State the function of plant hormones. 
(ii) Name a plant hormone if it is essential for cell division. 
(iii) Name the hormone which is involved in photosynthesis. Explain its role.

Ans. (i) Plant hormones help to coordinate growth, development, and responses to the environment. 

(ii) Cytokinins are a plant hormone that promotes cell division.

(iii) Auxin is the hormone that is involved in photosynthesis. 

When growing plants detect light, auxin, synthesized at the shoot tip, helps the cells 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 the shoot which is away from light. Thus, the plant appears to bend towards the light.

11. Name the hormone secreted by the thyroid gland and state its function. Why is it important for us to have or iodized salt in our diet? Name the disease caused due to the deficiency of iodine and mention its main symptoms.

Ans. Thyroxin hormone secreted by the thyroid gland and it regulates carbohydrate, protein, and fat metabolism in the body so as to provide the best balance for growth.

It is important for us to have or iodized salt in our diet because iodine is essential for the synthesis of thyroxin. In the case of iodine is deficient in our diet, there is a possibility that we might suffer from goiter. 

The symptoms of this disease is a swollen neck.

12. (i) Name the parts of the brain which control voluntary action, involuntary action.
(ii) What is the significance of the peripheral nervous system?
(iii) Name the components of this nervous system and distinguish between the origins of the two.

Ans. (i) The brain has three  major parts, namely the fore-brain, mid-brain and hind-brain which control voluntary and non-voluntary action.

Fore-brain is the main thinking part of the brain. Activities like walking in a straight line, riding a bicycle, picking up a pencil. These are possible due to a part of the hind-brain called the cerebellum.

Involuntary actions like blood pressure, salivation, vomiting, our mouth waters when we see the food we like without our meaning to, our hearts beat without our thinking about it, change in the size of the pupil are controlled by the medulla in the hind-brain.

(ii) The communication between the central nervous system and the other parts of the body is facilitated by the peripheral nervous system consisting of cranial nerve and spinal nerve.

Difference between the origins of the two - cranial nerves arising from the brain and spinal nerves arising from the spinal cord. 

13. Name various plant hormones. Also, gives their physiological effect on plant growth and development.

Ans.  Various plant hormons are auxin, gibberellins and cytokinins.

(i) Auxin - When growing plants detect light, a hormone called auxin, synthesized at the shoot tip, helps the cells 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 the shoot which is away from light. Thus, the plant appears to bend towards light.
(ii)  Gibberellins - Gibberellins help in the growth of the stem.
(iii) Cytokinins  -  Cytokinins promote cell division, and it is natural then that they are present in greater concentration in areas of rapid cell division, such as in fruits and seeds.
(iv) Abscisic acid - Plants also need signals to stop growing. Abscisic acid is one example of a hormone that inhibits growth. Its effects include wilting of leaves.

14. Draw and label the endocrine gland.

Ans. 

15. Draw and label the part of the neuron. What is the function of the neuron?

Ans. 

 nervous tissue is made up of an organised network of nerve cells or neurons, and is specialised for conducting information via electrical impulses from one part of the body to another.

16. Why is the flow of signals in a synapse from the axonal end of one neuron to the dendritic end of another neuron but not the reverse?

Ans. All information from our environment is detected by the specialised tips of some nerve cells called receptors. This information, acquired at the end of the dendritic tip of a nerve cell sets off a chemical reaction that creates an electrical impulse. This impulse travels from the dendrite to the cell body, and then along the axon to its end. At the end of the axon, the electrical impulse sets off the release of some chemicals. These chemicals cross the gap, or synapse, and start a similar electrical impulse in a dendrite of the next neuron. So the flow of signals in a synapse from the axonal end of one neuron to the dendritic end of another neuron but not the reverse.

17. (i) Which structure protects the spinal cord? 

(ii) Write an activity to show phototropism and geotropism 

(iii) What type of movement is shown by mimosa plant leaves when touched with a finger?

Ans. (i) The vertebral column or backbone protects the spinal cord.

(ii) (a) Fill a conical flask with water. 
(b) Cover the neck of the flask with a wire mesh. 
(c) Keep two or three freshly germinated beam seeds on the wire mesh. 

(d) Take a cardboard box that is open from one side.
(e) Keep the flash in the box in such a manner that the open side of the box faces light coming from a window. 
(f) After two or three days, we will notice that the shoots bend towards light and roots away from light.
(g) Now turn the flask so that the shoots are away from light and the roots towards the light. Leave it undisturbed in this condition for a few days.
(iii) Nastic movement.

18. Explain how the human body responds when adrenaline is secreted into the blood.
Ans.Adrenaline is secreted directly into the blood from the adrenal glands and carried to different parts of the body. Example the specific tissues on which it acts include the heart. Due to this the heart beats faster, resulting in the supply of more oxygen to our muscles. Due to the contraction of muscles around small arteries in these organs the blood to the digestive system and skin is reduced . This diverts the blood to our skeletal muscles. The rate of breathing increases because of the contractions of the diaphragm and the rib muscles.  Due to all these responses together enable the animal body to be ready to deal with the situation. 

19. Mention one role of each of the following:
(i) Cerebellum for brain (ii) Medulla (iii) Forebrain.
Ans. (i) Activities like walking in a straight line, riding a bicycle, picking up a pencil, all are controlled by a part of the hind-brain called the cerebellum. It is also responsible for the precision of voluntary actions and maintaining the posture and balance of the body.
(ii) Involuntary actions like our mouth waters when we see food, blood pressure, change in the size of the pupil, salivation, and vomiting are controlled by the medulla in the hind-brain.
(iii) Fore-brain is the main thinking part of the brain. It receives sensory impulses from various receptors. Forebrain controls body temperature, blood sugar, hunger, sensory signals. It also controls motor which controls the movement of voluntary muscles,

Class X Solution OF CH-6 LIFE PROCESSES

I. Very short answer type questions:                                  

1. If salivary amylase is lacking in the saliva, which events in the mouth cavity will be affected?
Ans. It will affect the breakdown of starch because the saliva contains an enzyme called salivary amylase that breaks down starch. 

2. Name the secretion by which the inner lining of the stomach is protected by hydrochloric acid.
Ans. The gastric gland present in the wall of the stomach secrets mucus protects the inner lining of the stomach from the action of the acid under normal conditions. 

3. During deficiency of oxygen in tissues of human beings, which acid is converted into lactic acid?
Ans. During deficiency of oxygen in tissues of human beings, pyruvate is converted into lactic acid which is a three-carbon molecule.

4. What is common for Cuscuta, ticks, and leeches?
Ans. All are parasitic plants and these parasitic plants derive nutrition from plants or animals without killing them.

5. What are the functions of gastric glands present in the wall of the stomach?
Ans. The gastric glands present in the wall of the stomach release hydrochloric acid, a protein-digesting enzyme called pepsin and mucus.

6. How can you test that the rice water contains starch?
Ans. If a few drops of iodine were added to the rice water which contains starch, the colour of starch turns into blue-black in colour.

7. What is the function of pancreatic juice?
Ans. The pancreas secretes pancreatic juice which contains enzymes like trypsin for digesting proteins and lipase for breaking down emulsified fats.

8. Where does aerobic respiration occur in a cell?
Ans. Aerobic respiration takes place in the cytoplasm of a cell.

9. What will happen if platelets were absent in blood?
Ans. When we are injured and start bleeding platelets help to clot the blood at these points of injury because the loss of blood from the system would lead to a loss of pressure which would reduce the efficiency of the pumping system. 

10. What is the role of acid in our stomach?
Ans. The hydrochloric acid creates an acidic medium which facilitates the action of the enzyme pepsin and kills bacteria and harmful organisms that may be present in food.

11. Define transpiration.
Ans. The loss of water in the form of vapour from the aerial parts of the plant is known as transpiration.

12. When air is blown from the mouth into a test tube containing lime water, the lime water turns milky. Why?
Ans. The air that is blown from the mouth contains carbon dioxide gas and when carbon dioxide gas reacts with lime water to form insoluble calcium carbonate and limewater turn milky.

13. State the function of digestive enzymes.
Ans. Digestive enzymes help to break the complex molecules of food particles into simpler molecules and helps in digestion.

14. During respiration where does, the exchange of gas takes place?
Ans. In human, the alveoli provide a surface where the exchange of gases can take place and in-plant massive amounts of gaseous exchange take place in the leaves through stomata.

15. Write the correct sequence of anaerobic respiration in yeast.
Ans. Break down of glucose ( in the cytoplasm)→ Pyruvate → Breakdown of pyruvate ( in the absence of oxygen) → ethanol + carbon dioxide. 

16. Write the correct sequence of aerobic respiration.
Ans. Break down of glucose → Pyruvate → Breakdown of pyruvate ( in the mitochondria and in the presence of oxygen) → Carbon dioxide + water + energy. 

17. Write the correct sequence of air passing during inhalation.
Ans. Nostril → Pharynx → Larynx → Trachea →  Lungs (Alveoli)

18. Name the tissues that transport 
(i) water and mineral in a plant 
(ii) transport soluble product of photosynthesis in plants.
Ans. (i) Xylem transport water and 
(ii) phloem transport soluble product of photosynthesis.

19. Where does the digestion of fat take place in our bodies?
Ans. The digestion of fat takes place in the small intestine in our bodies.

20. What is the role of saliva in the digestion of food?
Ans. Saliva is secreted by the salivary gland and helps in digestion. The saliva contains an enzyme called salivary amylase, during digestion saliva breaks down starch which is a complex molecule to give sugar.  

21. What are the final products of carbohydrates, protein, and fats after their digestion?
Ans. The final products of carbohydrates, protein, and fats after their digestion are glucose, amino acids, and fatty acids respectively?

22. Stomata of desert plants remain closed during the daytime? How do they take up CO₂ and perform photosynthesis?
Ans. Desert plants take up carbon dioxide at night and prepare an intermediate which is acted upon by the energy absorbed by the chlorophyll during the day.

23. Write two major components of human urine.
Ans. Water and uric acid are the major components of human urine.

24. A major amount of water selectively reabsorbed by the tubular part of the nephron in humans. What are the two factors on which the amount of water reabsorbed depends?
Ans. The amount of water reabsorbed depends on how much excess water there is in the body, and on how much of dissolved waste there is to be excreted.

25. What happens to glucose, amino acids, salt and water that enter the nephron along with filtrate?
Ans. Substances in the initial filtrate, such as glucose, amino acids, salts and a major amount of water, are selectively re-absorbed as the urine flows along the tube.  

26. Why is diffusion not sufficient to meet the oxygen requirements of all the cells in multicellular organisms?

Ans. In multicellular organisms, the body size of animals is large, the diffusion pressure alone cannot take care of oxygen delivery to all parts of the body.

27. Write the equation of photosynthesis?
Ans. Equation of photosynthesis is :
6CO₂ + 6H₂O + (Chlorophyll+ Sunlight)→ C₆H₁₂O₆  + 6O₂
                                                            Glucose 
28. Name the energy currency in the living organism. When and where it is produced?
Ans. The energy currency in the living organism is adenosine triphosphate ATP. It is produced during photosynthesis in plants and is stored in mitochondria in the cell.

29. What is the structural and functional unit of the kidney?
Ans. A nephron is the structural and functional unit of the kidney.

30. On which of the opening and closing of the stomatal pore depends? 
Ans. The opening and closing of the stomatal pore depend on the guard cells.

II. Short answer type questions: 

1. How does the guard cell regulate opening and closing the stomatal pores?
Ans.  The opening and closing of the pore is a function of the guard cells. The guard cells swell when water flows into them, causing the stomatal pore to open. Similarly, the pore closes if the guard cells shrink.

2. State any two differences between arteries and veins. 
Ans. Two differences between arteries and veins are: 
i. Arteries carry blood away from the heart to various organs of the body whereas veins collect the blood from different organs and bring it back to the heart.
ii. Since the blood emerges from the heart under high pressure, the arteries have thick, elastic walls. whereas veins have thin walls because the blood is no longer under pressure, instead they have valves that ensure that the blood flows only in one direction.

3. What function is served by the following: 
(i) gastric sphincter (ii) anal sphincter.
Ans. (i) The exit of food from the stomach is regulated by a sphincter muscle which releases it in small amounts into the small intestine.
(ii) The exit of waste which is unabsorbed food material is regulated by the anal sphincter.

4. List any four strategies used by plants for excretion.
Ans. (i) They can get rid of excess water by transpiration through stomata.
(ii)  Many plant waste products are stored in cellular vacuoles. 
(iii) In the plant many of their tissues consist of dead cells and these waste products may be stored in leaves that fall off.
(iv) Other waste products are stored as resins and gums, especially in old xylem.     

5. Leaves of a healthy potted plant were coated with Vaseline. Will these plants remain healthy for long? Give reasons for your answer.
Ans. If the leaves of a healthy potted plant were coated with Vaseline then these plants will not remain healthy for a long time and die because the vaseline layer prevents the plant from receiving sunlight, photosynthesis, respiration, and transpiration.  

6. Write three differences between aerobic and anaerobic respiration.
Ans. Three differences between aerobic respiration are :
(i) aerobic respiration takes place in the presence of air (oxygen) and anaerobic respiration takes place in the absence of air.
(ii) The aerobic respiration takes place in the mitochondria and anaerobic respiration takes place in the cytoplasm. 
(iii) In aerobic respiration, pyruvate converted into carbon dioxide, water, and energy in form of ATP and in anaerobic respiration pyruvate converted into ethanol and carbon dioxide.

7. What is the internal energy that reserve in plants? 
Ans. The carbohydrates which are not used immediately are stored in the form of starch, which serves as the internal energy reserve to be used as and when required by the plant

8. How do leaves of plants help in excretion?
Ans. Many plant waste products are stored in cellular vacuoles. Waste products may be stored in leaves that fall off. 

9. Differentiate between and autotrophs and heterotrophs.
Ans. Autotrophic nutrition involves the intake of simple inorganic materials from the environment and using an external energy source like the Sun to synthesise complex high-energy organic material. 
Heterotrophic nutrition involves the intake of complex material prepared by other organisms. 

10. How is the process of transpiration useful for plants?
Ans. Transpiration helps in the absorption and upward movement of water and minerals dissolved in it from roots to the leaves. It also helps in temperature regulation.

11. Plants have low energy needs as compared to animals. Explain.
Ans. Plants have low energy needs as compared to animals because plants do not move, and plant bodies have a large proportion of dead cells in many tissues.

12. How are the alveoli designs to maximize the exchange of gases?
Ans. The alveoli provide a surface where the exchange of gases can take place. The walls of the alveoli contain an extensive network of blood vessels that helps in maximizing the exchange of gas.

13. When a sportsman runs, he often gets muscle cramps. Why?
Ans. When a sportsman runs the rate of consumption of oxygen is more than the rate of supply of oxygen so, in order to fulfill that, the body starts anaerobic respiration. In this process, pyruvic acid converted to lactic acid and it accumulates in the muscles and feels muscle cramps.

14. What is the adaptation of leaf for photosynthesis?
Ans. Leaves have a large surface area to catch more light from the sun. Leaf contain many chloroplasts that allow light to be converted into chemical energy. It has stomata which are tiny pores present on the surface of the leaves and helps in the exchange of gases. Stomata contain guard cells that control the opening and closing of the pores of the stomata.

15. Some finger-like projections are present in the inner wall of a small intestine write their names? Why are they important or List their functions?
Ans. Finger-like projections are present in the inner wall of a small intestine are called villi.
The digested food is taken up by the villi and is richly supplied with blood vessels that take the absorbed food to each and every cell of the body, where it is utilised for obtaining energy, building up new tissues and the repair of old tissues.

16. Name the extensively coiled structure of the elementary Canal. Compare the length of the small intestine in herbivores and carnivores.
Ans. The small intestine is the longest part of the elementary canal which is fitted into a compact space because of extensive coiling. The length of the small intestine differs in various animals depending on the food they eat. Herbivores eating grass need a longer small intestine to allow the cellulose to be digested. Meat is easier to digest, hence carnivores like tigers have a shorter small intestine.

17. List the events that occur during the process of photosynthesis.
Ans. The following events occur during this process of photosynthesis –
(i) Absorption of light energy by chlorophyll. 
(ii) Conversion of light energy to chemical energy and splitting of water molecules into hydrogen and oxygen. 
(iii) Reduction of carbon dioxide to carbohydrates.

18. List the three kinds of blood vessels of the human circulatory system and write their functions in tabular form.
Ans. The three kinds of blood vessels of the human circulatory system are arteries, capillaries, and veins.
Arteries are the vessels that carry blood away from the heart to various organs of the body. 
The exchange of material between the blood and surrounding cells takes place across this thin wall of the capillaries. The capillaries then join together to form veins that convey the blood away from the organ or tissue.
Veins collect the blood from different organs and bring it back to the heart.

19. Name three different glands associated with the digestive system in humans. Also, name their secretions.
Ans. Salivary glands secrete saliva. The saliva contains an enzyme called salivary amylase that breaks down starch which is a complex molecule to give sugar. The food is mixed thoroughly with saliva and moved around the mouth while chewing by the muscular tongue.
Liver the largest gland secrets bile juice which breaks large globules of fat, down into smaller globules increasing the efficiency of enzyme action.
And third is the pancreas that secrets pancreatic juice which contains enzymes like trypsin for digesting proteins and lipase for breaking down emulsified fats.

20. Why do the walls of the trachea not collapse when there is less air in it.
Ans. The walls of the trachea do not collapse because the trachea is supported by rings of cartilage which hold them in place and provides support to the trachea which does not collapse even when there is less air in it.   

21. What are villi?  Explain their functions in the digestive system.
Ans. The inner the lining of the small intestine has numerous finger-like projections called villi which increases the surface area for absorption. The villi are richly supplied with blood vessels that take the absorbed food to each and every cell of the body, where it is utilised for obtaining energy, building up new tissues and the repair of old tissues.

22. Define transpiration. States it's two functions.
Ans. The loss of water in the form of vapour from the aerial parts of the plant is known as transpiration.
Transpiration helps in the absorption and upward movement of water and minerals dissolved in it from roots to the leaves. It also helps in temperature regulation.

23. Why do ventricles have thicker muscular walls than atria?
Ans. Since ventricles have to pump blood into various organs, they have thicker muscular walls than the atria do. Valves ensure that blood does not flow backward when the atria or ventricles contract.

24. What is the peristaltic movement?
Ans. The lining of the canal has muscles that contract rhythmically in order to push the food forward. This is called peristaltic movements that occur all along the gut.
It is very important for the movement of food to the stomach and the bowels down the anus.

25. Name the enzymes present in pancreatic juice and give their functions.
Ans. Pancreatic juice contains enzymes like trypsin for digesting proteins and lipase for breaking down emulsified fats.

26. List three characteristics of lungs which make it an efficient respiratory surface.
Ans. Lungs contain balloon-like structure alveoli which provide a surface where the exchange of gases can take place.
The walls of the alveoli contain an extensive network of blood vessels.
The lungs always contain a residual volume of air so that there is sufficient time for oxygen to be absorbed and for the carbon dioxide to be released. 

27. Why does the absorption of digested food occur mainly in the small intestine?
Ans. The inner lining of the small intestine has numerous finger-like projections called villi which increase the surface area for absorption and the digested food is taken up by the walls of the intestine. The villi are richly supplied with blood vessels that take the absorbed food to each and every cell of the body, where it is utilised for obtaining energy, building up new tissues and the repair of old tissues.

28. What is excretion? How do unicellular organisms remove their wastes?
Ans. The biological process involved in the removal of harmful metabolic wastes (gaseous wastes generated during photosynthesis or respiration. Other metabolic activities generate nitrogenous materials) from the body is called excretion.

29. Name the material transported by the following:
(a) xylem (b) Pulmonary artery (c) Pulmonary veins (d) Phloem.
Ans. (a) Xylem transport water and mineral from the soil through the roots.
(b) The pulmonary artery carries deoxygenated blood from the right ventricle to the lungs.
(c) Thew pulmonary veins carry oxygenated blood from the lungs to the heart.
(d) Phloem transports products of photosynthesis from the leaves where they are synthesised to other parts of the plant.  

30. Explain the significations of peristaltic movement that occur all along the gut during digestion.
Ans. It is necessary to move the food in a regulated manner along the digestive tube so that it can be processed properly in each part. The lining of the canal has muscles that contract rhythmically in order to push the food forward. This is called peristaltic movements and occurs all along the gut.

31. Which mechanism plays an important role in the transportation of water in Plants? (i) during daytime (ii) at night.
Ans. (i) During the day when the stomata are open, the transpiration pull becomes the major driving force in the movement of water in the xylem.
(ii) At night the effect of root pressure in the transport of water is more important. 

32. Why does the medium become acidic in the mouth? What is the ill effect of this acidic medium? How can this be prevented?
Ans. (i) Bacteria present in the mouth produce acids by the fermentation of sugar and food particles in the mouth.
 (ii) The enamel of the tooth gets corroded by the action of acids and tooth decay occurs.
 (iii) By cleaning the teeth with toothpaste which is basic in nature and neutralise acids.

33. What is translocation? How it takes place in plants?
Ans. The transport of soluble products of photosynthesis is called translocation. 
Translocation occurs in the part of the vascular tissue known as phloem. The translocation of food and other substances takes place in the sieve tubes with the help of adjacent companion cells both in upward and downward directions.

34. Name the substrates from the following enzyme:
Trypsin, Amylase, Pepsin, and Lipase.
Ans. The substrate for :
trypsin -  is pancreatic juice release from the pancreas.
amylase - is Saliva release from the salivary gland.
pepsin -  is protein-digesting enzyme secrets from gastric glands.
lipase - is pancreatic juice release from the pancreas.

35. Why do we feel a cramp in our muscles during certain physical activities?
Ans. During some activities like exercise, running the rate of consumption of oxygen is more than the rate of supply of oxygen so, in order to fulfill that, the body starts anaerobic respiration, which is a process in which respiration takes place in the absence of oxygen. In this process, pyruvic acid converted to lactic acid and it accumulates in the muscles and feels muscle cramps.

III. Long answer type questions:

1. Why do aquatic animals have a faster rate of breathing compared to terrestrial animals? Name the enzyme present in saliva and state its function.
II. Draw the diagram of the human respiratory system and label the following:
(i) The part where the air is filtered by the fine hair mucus,
(ii) The part which terminates balloon-like structure, 
(iii) The balloon-like structure where the exchange of gases takes place, 
(iv) The part which separates the chest cavity from the abdominal cavity.
Ans. I. Since the amount of dissolved oxygen is fairly low compared to the amount of oxygen in the air, the rate of breathing in aquatic organisms is much faster than that seen in terrestrial organisms. Fishes take in water through their mouths and force it past the gills where the dissolved oxygen is taken up by the blood.
Pancreatic juice contains enzymes - trypsin and lipase .

The function of trypsin - it helps in digesting proteins. 

The function of lipase - it helps in breaking down emulsified fats. 
II. 

2. Describe the flow of blood through the heart of human beings.
Ans.  The heart has different chambers to prevent the oxygen-rich blood from mixing with the blood-containing carbon dioxide. The carbon dioxide-rich blood has to reach the lungs for the carbon dioxide to be removed, and the oxygenated blood from the lungs have to be brought back to the heart.This oxygen-rich blood is then pumped to the rest of the body.
De-oxygenated blood comes from the body to the upper chamber on the right, the right atrium, as it expands. As the right atrium contracts, the corresponding lower chamber, the right ventricle, dilates. This transfers blood to the right ventricle, which in turn pumps it to the lungs for oxygenation.
Oxygen-rich blood from the lungs comes to the thin-walled upper chamber of the heart on the left, the left atrium. The left atrium relaxes when it is collecting this blood. It then contracts, while the next chamber, the left ventricle, expands, so that the blood is transferred to it. When the muscular left ventricle contracts in its turn, the blood is pumped out to the body.  

3. Describe the process of urine formation in the kidney.
Ans. The kidney has a cluster of very thin-walled blood capillaries. Each capillary cluster in the kidney is associated with the cup-shaped end of a tube that collects the filtered urine.
Each kidney has large numbers of these filtration units called nephrons packed close together. Some substances in the initial filtrate, such as glucose, amino acids, salts and a major amount of water, are selectively re-absorbed as the urine flows along the tube. The amount of water reabsorbed depends on how much excess water there is in the body, and on how much of dissolved waste there is to be excreted. The urine forming in each kidney eventually enters a long tube, the ureter, which connects the kidneys with the urinary bladder. Urine is stored in the urinary bladder until the pressure of the expanded bladder leads to the urge to pass it out through the urethra.  

4. Why is blood circulation in the human heart called double circulation?Ans. The blood circulation in the human heart is called double circulation because the blood passes through the heart twice in one complete cycle of the body.
Once - Oxygen-rich blood from the lungs comes to the thin-walled upper chamber of the heart on the left, the left atrium. The left atrium relaxes when it is collecting this blood. It then contracts, while the next chamber, the left ventricle, expands, so that the blood is transferred to it. When the muscular left ventricle contracts in its turn, the blood is pumped out to the body.
Second -  De-oxygenated blood comes from the body to the upper chamber on the right, the right atrium, as it expands. As the right atrium contracts, the corresponding lower chamber, the right ventricle, dilates. This transfers blood to the right ventricle, which in turn pumps it to the lungs for oxygenation.
What is the advantage of having a four-chambered heart?

5. With the help of a schematic flow chart, show the breakdown of glucose in a cell to provide energy:
(i) in the presence of oxygen 
(ii) in the absence of oxygen
(iii) when there is a lack of oxygen.
Ans. 

6. I. Name the following:
 (i) The process in plants that links light energy with chemical energy
 (ii) Organisms that cannot prepare their own food.
 (iii) An enzyme secreted from gastric glands in the stomach act on protein.
 (iv) Cells that surround a stomatal pore.
 (v) The cell organelle where photosynthesis occurs.
II.  (i) List two functions performed by dilute hydrochloric acid in our stomach.
(ii) Name the raw materials required for photosynthesis.
Ans. I. (i) Photosynthesis - is the process in plants that links light energy with chemical energy.
(ii) Heterotrophs - that cannot prepare their own food.
(iii) Pepsin, and mucus - a protein-digesting enzyme.
.(iv) Guard cells - that surround the stomata and regulate opening and closing the pores of stomata.
(v) Chloroplasts - the cell organelles contain green pigment chlorophyll and helps in photosynthesis.
II. (i) (a) The hydrochloric acid creates an acidic medium which converts pepsinogen into pepsin or facilitates the action of the enzyme pepsin.
(b) It kills bacteria and harmful organisms that may be present in food.
(ii) Carbon dioxide water sunlight and chlorophyll are the raw materials for photosynthesis.

7. I. Name the following:
(i) Where food is completely digested?
(ii) Juice contains trypsin enzymes.
(iii) Who secretes bile juice?
(iv) That absorbs water from an unabsorbed food.
(v) Two secretions released by a gastric gland.
II. List two major steps involved in the formation of urine and state in brief their functions.
Ans. I. (i) Food is completely digested in the small intestine.
(ii) Pancreatic juice secreted by the pancreas contains trypsin for digesting proteins.
(iii) The liver secretes bile juice to break large fat globules into smaller globules, increasing the efficiency of enzyme action. 
(iv) The large intestine absorbs water from unabsorbed food. 
(v) Hydrochloric acid and a protein-digesting enzyme called
pepsin.
II. There are three main steps of urine formation: 
(i) Filteration of blood- Each kidney has large numbers of filtration units called nephrons that consist of a tubule that is connected with collecting duct at one end a cup-shaped structure at the end and it is called bowmen's capsule. This filtrate contains glucose, amino-acid salts and a major amount of water.
(ii) Reabsorption - Useful substances like glucose, amino acids, salts and a major amount of water are filtered and reabsorbed as the urine flows along the tube.
(iii) Secretion -  The urine forming in each kidney eventually enters a long tube, the ureter, which connects the kidneys with the urinary bladder.

8. I. List the role of each of the following in our digestive system.
(i) Muscles of the stomach wall
(ii) Hydrochloric acid.
(iii) Mucus.
II. What is lymph? How is the composition of lymph different from blood plasma? List two functions of the lymphatic system.
Ans. I. (i) Role of muscles of the stomach wall -  The stomach is a large organ that expands when food enters it. The muscular walls of the stomach help in mixing the food thoroughly with more digestive juices.
(ii)  Role of hydrochloric acid - The gastric glands present in the wall of the stomach that releases hydrochloric acid. The hydrochloric acid creates an acidic medium that facilitates the action of the enzyme pepsin.
(iii)  Role of mucus -  The mucus that is secreted by the gastric gland, protects the inner lining of the stomach from the action of the acid under normal conditions. 
II. Lymph is a tissue fluid that helps in transpiration. Through the pores present in the walls of capillaries, some amount of plasma, proteins and blood cells escape into intercellular spaces in the tissues to form this tissue fluid (Lymph). 
It is colourless and contains less protein than blood plasma.
The function of the lymphatic system:
(i) Lymph carries digested and absorbed fat from intestine and 
(ii) drains excess fluid from extracellular space back into the blood.

9. Give reasons for :
(i) Oxygenated and Deoxygenated blood is separate in the heart of mammals.
(ii) Ventricles are thick-walled.
(iii) Herbivores have longer small intestine as compared to carnivores.
Ans. (i) The separation of the right side and the left side of the heart is useful to keep oxygenated and deoxygenated blood from mixing. Such separation allows a highly efficient supply of oxygen to the body. This is useful in animals that have high energy needs, such as birds and mammals, which constantly use energy to maintain their body temperature. 
(ii) Since ventricles have to pump blood into various organs, they have thicker muscular walls than the atria do. Valves ensure that blood does not flow backward when the atria or ventricles contract.
(iii)  The length of the small intestine differs in various animals depending on the food they eat. Herbivores eating grass need a longer small intestine to allow the cellulose to be digested. Meat is easier to digest, hence carnivores like tigers have a shorter small intestine.

10. Give reasons:
(i) Blood goes only once through the heart in fishes.
(ii) Plants have low energy needs.
(iii) What are capillaries?
Ans. (i) Fishes have only two chambers to their hearts and the blood is pumped to the gills, is oxygenated there, and passes directly to the rest of the body. Thus, blood goes only once through the heart in the fish during one cycle of passage through the body.
(ii)  Plants have low energy needs as compared to animals because plants do not move, and plant bodies have a large proportion of dead cells in many tissues.
(iii) On reaching an organ or tissue, the artery divides into smaller and smaller vessels to bring the blood in contact with all the individual cells. The smallest vessels have walls that are one-cell thick and are called capillaries. 

11. (a) Draw the human excretory system and label the following parts:
(i) left kidney (ii) urinary bladder (iii) vena cava (iv) Urethra (v) Left ureter (vi) Left renal vein (v)left renal artery.

(b) State the purpose of making urine.
(c) Name any two substances which are selectively reabsorbed from the tubules of the nephron.

Ans. (a) Excretory system in human beings:

(b) The purpose of making urine is to filter out waste products from the blood.  Nitrogenous waste such as urea or uric acid is removed from blood in the kidneys. 

(c) The amount of water reabsorbed depends on:
i. how much excess water there is in the body and
ii. on how much of dissolved waste there is to be excreted.

12. I. Draw a diagram of a cross-section of the human heart and label the following parts :
(i) Right ventricles (ii) Aorta (iii) Left atrium (iv) Pulmonary arteries.
II. Give reasons for the following:
(i) The muscular wall of the ventricles is thicker than the walls of the atria.
(ii) Arteries have thick elastic walls.
Ans. I.

II. (i) Since ventricles have to pump blood into various organs of the body, they have thicker muscular walls than the atria do. valves ensure that blood does not flow backward when the atria or ventricles contract.
(ii) Arteries are the vessels that carry blood away from the heart to various organs of the body. Since the blood emerges from the heart under high pressure, the arteries have thick, elastic walls.

13. Why is the rate of breathing in aquatic organisms much faster than terrestrial organisms?
Ans. Since the amount of dissolved oxygen is fairly low compared to the amount of oxygen in the air, so to take more oxygen, the rate of breathing in aquatic organisms is much faster than that seen in terrestrial organisms.
Fishes take oxygen in water through their mouths and force it past the gills where the dissolved oxygen is taken up by the blood. Terrestrial organisms use oxygen in the atmosphere for respiration. This oxygen is absorbed by different organs in different animals. All these organs have a structure that increases the surface area which is in contact with the oxygen-rich atmosphere  

14. Why and how does water enter continuously into the root xylem? Why is transpiration important for plants?
Ans. At the roots, cells in contact with the soil actively take up ions. This creates a difference in the concentration of these ions between the root and the soil. Water, therefore, moves into the root from the soil to eliminate this difference. This means that there is a steady movement of water into root xylem, creating a column of water that is steadily pushed upwards.

Transpiration is important for plants because transpiration helps in the absorption of water and upward movement of water and minerals dissolved in it from roots to the leaves. It also helps in temperature regulation. 

15. I. Name the factors on which the amount of water reabsorbed along the tubular part of the nephron depends on.
II. Draw a diagram of the human excretory system and label the following :
(i) part in which urine is produced
(ii) parts which store the urine
(iii) the part which connects (i) and(ii)
(iv) the part from which urine is passed out. Explain the process of nutrition in amoeba with the help of a diagram.
Ans. I. The amount of water reabsorbed depends on:
i. how much excess water there is in the body, and
ii.  on how much of dissolved waste there is to be excreted.
II. See the Long question-answer Q. 11.

16. I. Explain how paramecium obtains its food?
II. Draw a labelled diagram of the human alimentary canal and label the following parts; (i) Liver (ii) Pancreas (iii) Small intestine (iv) Large intestine (v) Oesophagus (vi) Gall bladder (vii) Stomach (viii) Appendix Ans. I. Paramoecium is a unicellular organism, the cell has a definite shape and food is taken in at a specific spot. Food is moved to this spot by the movement of cilia which covers the entire surface of the cell. Complex substances are broken down into simpler ones which then diffuse into the cytoplasm. The remaining undigested material is moved to the surface of the cell and thrown out.
II. Diagram of the human alimentary canal :

17. (a) Draw a diagram of an excretory unit of a human kidney (Nephron) and label the following: Bowman's capsule, glomerulus, collecting duct, tubular part of the nephron, and renal artery. 
(b) Write the important functions of the structural and functional unit of the kidney.
(c) Write any one function of an artificial kidney. 
Ans. (a)

(b) The structural and functional unit of the kidney is nephron. It is the filtration unit of the kidney. First, the blood reaches the glomerules (consists of a cluster of thin-walled blood capillaries) and then filtrate in bowmen's capsule ( is a cup-shaped end of a tube in which each capillary cluster in the kidney is associated with this and this capsule collects the filtered urine). The filtrate that contains glucose, amino acids, salts and a major amount of water, are selectively re-absorbed as the urine flows along the tube and it gets collected in collecting duct and then stored in the urinary bladder.
(c) An artificial kidney is a device, it removes nitrogenous waste products from the blood through dialysis.

18. I. Explain the mechanism of photosynthesis.
How the transport of materials in xylem and phloem does occur? What is translocation?
II. II. Draw a diagram of a cross-section of a leaf and label the following part:
(i) chloroplast (ii) cuticle.
Ans. I. Mechanism of photosynthesis-  Photosynthesis is the process by which plants take in outside substances like carbon dioxide and water and convert them into carbohydrates in the presence of sunlight and chlorophyll. 
Chlorophyll is a green pigment and helps to convert the energy of sunlight into chemical energy. During photosynthesis, chlorophyll absorbs energy and then transforms water and carbon dioxide into oxygen and carbohydrates.
Carbohydrates are utilised for providing energy to the plant. The carbohydrates which are not used immediately are stored in the form of starch, which serves as the internal energy reserve to be used as and when required by the plant. 
6CO + 6H2O + Chlorophyll + Sunlight → C6H12O6 + O2
                                                           ( Glucose)
II. 

19. In human alimentary canal name the site of the complete digestion of various components of food. Explain the process of digestion.
Ans. The small intestine is the site of the complete digestion of carbohydrates, proteins, and fats. It receives the secretions of the liver and pancreas.
The pancreas secretes pancreatic juice which contains enzymes like trypsin for digesting proteins and lipase for breaking down emulsified fats.
The liver secretes bile juice break fats that are present in the intestine in the form of large globules. The walls of the small intestine contain glands that secrete intestinal juice which convert the proteins to amino acids, complex carbohydrates into glucose and fats into fatty acids and glycerol. The digested food is taken up by the walls (contain villi)of the intestine where it is utilised for obtaining energy, building up new tissues and the repair of old tissues. The unabsorbed food is sent into the large intestine.