Intext Questions

Q.1       What is the difference between a reflex action and walking?
Sol.

Walking is a voluntary action and is part of routine activities. On the other hand, reflex action is involuntary and happens as a response to a sudden danger to a voluntary organ.

---

Q.2       What happens at the synapse between two neurons?
Sol.

Transmission of nerve impulses between two neurons takes place at through the synapse. The axon terminal of a neuron releases specialized chemicals; called neurotransmitters. These chemicals travel through the synapse and reach the dendrites of the next neuron. The nerve impulses travel along with the neurotransmitters.

---

Q.3       Which part of the brain maintains posture and equilibrium of the body?
Sol.        Cerebellum

---

Q.4       How do we detect the smell of an agarbatti (incense stick)?
Sol.

The olfactory receptors; present in the nostrils; pick the smell. They send signals to the brain. The brain interprets those signals and we detect the smell of an incense stick.

---

Q.5      What is the role of the brain in reflex action?
Sol.

Brain has no direct involvement in reflex action. Reflex action is mainly controlled at the level of spinal cord.

---

Q.6       What are plant hormones?
Sol.        Plant hormones are special chemicals which regulate the growth of various plant parts.

---

Q.7       How is the movement of leaves of the sensitive plant different from the movement of a shoot towards light?
Sol.

The movement of leaves of the sensitive plant is a nastic movement, i.e. it does not depend on the direction of the stimulus. On the other hand, the movement of a shoot towards light is a tropic movement, i.e. it depends on the direction from which light is coming.

---

Q.8       Give an example of a plant hormone that promotes growth.
Sol.       Auxin

---

Q.9       How do auxins promote the growth of a tendril around a support?

Sol.

Auxin increase in concentration in the part of the tendril which is away from the support. This results in increased cell division in that part. The part which is nearer to the support has lesser rate of cell division. As a result, the external part of the tendril grows more than the internal part and the tendril coils around the support.

---

Q.10       Design an experiment to demonstrate hydrotropism.
Sol.

Following things are required for this experiment:
Seeds of bean, a deep tray, sand, a porous flower pot

Procedure:
(i) The tray should be big enough to accommodate the porous pot.
(ii) Fill the tray with sand and insert some seeds in it.
(iii) Make a pit in the sand and insert the porous pot in it.
(iv) Fill the porous pot with water.
(v) Leave the set up for about a week.

Observation: After a week when seeds are taken out, it is observed that roots grow in the direction of the porous pot. This shows hydrotropic movement in roots.

---

Q.11       How does chemical coordination take place in animals?
Sol.

Chemical coordination in animals takes place through hormones. There are several endocrine glands which secrete various kinds of hormones. These hormones regulate different functions in the body. For example; insulin is a hormone which regulates the blood sugar level.

---

Q.12       Why is the use of iodised salt advisable?
Sol.

Iodine is an important constituent of the hormone thyroxine. Iodine deficiency leads to a disease called goiter. Iodised salt is advised to prevent chances of goiter.

---

Q.13       How does our body respond when adrenaline is secreted into the blood?
Sol.

Adrenaline is also known as ‘fight or flight’ hormone. It prepares the body for emergency situations. Increased secretion of adrenaline in the blood increases the blood supply to limbs and to the facial area. It increases the heart rate and breathing rate so that more oxygen could be supplied to the limbs. Slight precipitation also occurs on the temple and in palms. All of this shows readiness for a fight or; if need be; a flight from the scene.

---

Q.14       Why are some patients of diabetes treated by giving injections of insulin?
Sol.

Insulin plays an important role in sugar metabolism. In some patients of diabetes insulin secretion is reduced. Insulin injection is given to such patients to compensate for reduced insulin secretion. Such cases of diabetes are called Insulin Dependent Diabetes Mellitus (IDDM).

Exercise

Q.1       Which of the following is a plant hormone?
             (a) Insulin                                                  (b) Thyroxin
             (c) Oestrogen                                           (d) Cytokinin
Sol.        (d) Ctyokinin

---

Q.2       The gap between two neurons is called a
              (a) Dendrite                                             (b) Synapse
              (c) Axon                                                   (d) Impulse
Sol.        (b) Synapse

---

Q.3        The brain is responsible for
               (a) Thinking                                             (b) Regulating the heart beat
               (c) Balancing the body                            (d) All of the above
Sol.         (d) All of the above

---

Q.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?

Sol.

Receptors provide information about the external environment so that the brain can instruct a related to organ to take necessary action. Receptors play an important role in our survival. Let us take the example of a person with hearing impairment. Certain ordinary task would be very difficult for that person. For example; while walking on the road, the person needs to hear the sound of vehicles moving near him. Without hearing those sounds, he would not be in a position to move safely on the road.

---

Q.5       Draw the structure of a neuron and explain its function.
Sol.

Function of Neuron: Neuron transmits the nerve impulses.

---

Q.6       How does phototropism occur in plants?
Sol.

Concentration of auxin changes in a particular plant part, in response to the direction of light. For example; in a stem, concentration of auxin increases in those parts which are away from light. This increases cell division in that part and thus the stem bends towards light. That is how phototropism occurs in plants.

---

Q.7        Which signals will get disrupted in case of a spinal cord injury?
Sol.

The spinal nerves go to the organs which are below the head region. Moreover, the autonomous nervous system is also connected to the spinal cord. In case of spinal cord injury, communication between the spinal nerves and the brain would be disturbed. Similarly, the communication between the autonomous nervous system and brain would also be disturbed; in case of spinal cord injury.

---

Q.8       How does chemical coordination occur in plants?
Sol.

Plant hormones play their roles in chemical coordination. Most of the plant hormones promote growth in certain plant parts, e.g. auxin, gibberellins and cytokinin. Abscissic acid is a plant hormone which inhibits growth. Shedding of leaves or ripe fruits is facilitated by abscissic acid.

---

Q.9       What is the need for a system of control and coordination in an organism?
Sol.

A living being does not live in isolation. It has to constantly interact with its external environment and has to respond properly for its survival. For example; when a hungry lion spots a deer, the lion has to quickly make a move so that it can have its food. On the other hand, the deer needs to quickly make a move to run for its life.

---

Q.10       How are involuntary actions and reflex actions different from each other?
Sol.

Involuntary actions are part of routine activities, while reflex actions are in response to a sudden danger. Moreover, involuntary actions happen in involuntary organs, while reflex action happens in a voluntary organ.

---

Q.11       Compare and contrast nervous and hormonal mechanisms for control and coordination in animals.
Sol.

Nervous control is fast, while hormonal control is slow. Nervous control is facilitated by neurotransmitters, while hormonal control is facilitated by hormones.

---

Q.12       What is the difference between the manner in which movement takes place in a sensitive plant and the movement in our legs?
Sol.

The movement in a sensitive plant is facilitated by chemical control, while the movement in our legs is facilitated by nervous control.

Exemplar

Multiple Choice Questions

Q.1 Which of the following statements is correct about receptors?

(a) Gustatory receptors detect taste while olfactory receptors detect smell

(b) Both gustatory and olfactory receptors detect smell

(c) Auditory receptors detect smell and olfactory receptors detect taste

(d) Olfactory receptors detect taste and gustatory receptors smell

Sol. (a)

---

Q.2 Electrical impulse travels in a neuron from

(a) Dendrite → axon → axonal end → cell body

(b) Cell body → dendrite → axon → axonal end

(c) Dendrite → cell body → axon → axonal end

(d) Axonal end → axon → cell body → dendrite

Sol. (c)

---

Q.3 In a synapse, chemical signal is transmitted from

(a) dendritic end of one neuron to axonal end of another neuron

(b) axon to cell body of the same neuron

(c) cell body to axonal end of the same neuron

(d) axonal end of one neuron to dendritic end of another neuron

Sol. (d)

---

Q.4 In a neuron, conversion of electrical signal to a chemical signal occurs at/in

(a) cell body

(b) axonal end

(c) dendritic end

(d) axon

Sol. (b)

---

Q.5 Which is the correct sequence of the components of a reflex arc?

(a) Receptors → Muscles → Sensory neuron → Motor neuron → Spinal cord

(b) Receptors → Motor neuron → Spinal cord → Sensory neuron → Muscle

(c) Receptors  → Spinal cord → Sensory neuron → Motor neuron → Muscle

(d) Receptors → Sensory neuron → Spinal cord → Motor neuron → Muscle

Sol. (d)

---

Q.6 Which of the following statements are true?

(i) Sudden action in response to something in the environment is called reflex action

(ii) Sensory neurons carry signals from spinal cord to muscles

(iii) Motor neurons carry signals from receptors to spinal cord

(iv) The path through which signals are transmitted from a receptor to a muscle or a gland is called reflex arc.

(a) (i) and (ii)

(b) (i) and (iii)

(c) (i) and (iv)

(d) (i) , (ii) and (iii)

Sol. (c)

---

Q.7 Which of the following statements are true about the brain?

(i) The main thinking part of brain is hind brain

(ii) Centres of hearing, smell, memory, sight etc are located in fore brain.

(iii) Involuntary actions like salivation, vomiting, blood pressure are controlled by the medulla in the hind brain

(iv) Cerebellum does not control posture and balance of the body

(a) (i) and (ii)

(b) (i), (ii) and (iii)

(c) (ii) and (iii)

(d) (iii) and (iv)

Sol. (c)

---

Q.8 Posture and balance of the body is controlled by

(a) cerebrum

(b) cerebellum

(c) medulla

(d) pons

Sol. (b)

---

Q.9 Spinal cord originates from

(a) cerebrum

(b) medulla

(c) pons

(d) cerebellum

Sol. (b)

---

Q.10 The movement of shoot towards light is

(a) geotropism

(b) hydrotropism

(c) chemotropism

(d) phototropism

Sol. (d)

---

Q.11 The main function of abscisic acid in plants is to

(a) increase the length of cells

(b) promote cell division

(c) inhibit growth

(d) promote growth of stem

Sol. (c)

---

Q.12 Which of the following is not associated with growth of plant?

(a) Auxin

(b) Gibberellins

(c) Cytokinins

(d) Abscisic acid

Sol. (d)

---

Q.13 Iodine is necessary for the synthesis of which hormone?

(a) Adrenaline

(b) Thyroxin

(c) Auxin

(d) Insulin

Sol. (b)

---

Q.14 Choose the incorrect statement about insulin

(a) It is produced from pancreas

(b) It regulates growth and development of the body

(c) It regulates blood sugar level

(d) Insufficient secretion of insulin will cause diabetes

Sol. (b)

---

Q.15 Select the mis-matched pair

(a) Adrenaline : Pituitary gland

(b) Testosterone: Testes

(c) Estrogen : Ovary

(d) Thyroxin : Thyroid gland

Sol. (a)

---

Q.16 The shape of guard cells changes due to change in the

(a) protein composition of cells

(b) temperature of cells

(c) amount of water in cells

(d) position of nucleus in the cells

Sol. (c)

---

Q.17 The growth of tendril in pea plants is due to

(a) effect of light

(b) effect of gravity

(c) rapid cell divisions in tendrillar cells that are away from the support

(d) rapid cell divisions in tendrillar cells in contact with the support

Sol. (c)

---

Q.18 The growth of pollen tubes towards ovules is due to

(a) hydrotropism

(b) chemotropism

(c) geotropism

(d) phototropism

Sol. (b)

---

Q.19 The movement of sunflower in accordance with the path of sun is due to

(a) phototropism

(b) geotropism

(c) chemotropism

(d) hydrotropism

Sol. (a)

---

Q.20 The substance that triggers the fall of mature leaves and fruits from plants is due to

(a) auxin

(b) gibberellin

(c) abscisic acid

(d) cytokinin

Sol. (c)

---

Q.21 Which of the following statements about transmission of nerve impulse is incorrect?

(a) Nerve impulse travels from dendritic end towards axonal end

(b) At the dendritic end electrical impulses bring about the release of some chemicals which generate an electrical impulse at the axonal end of another neuron

(c) The chemicals released from the axonal end of one neuron cross the synapse and generate a similar electrical impulse in a dendrite of another neuron

(d) A neuron transmits electrical impulses not only to another neuron but also to muscle and gland cells

Sol. (b)

---

Q.22 Involuntary actions in the body are controlled by

(a) medulla in fore brain

(b) medulla in mid brain

(c) medulla in hind brain

(d) medulla in spinal cord

Sol. (c)

---

Q.23 Which of the following is not an involuntary action?

(a) Vomiting

(b) Salivation

(c) Heart beat

(d) Chewing

Sol. (d)

---

Q.24 When a person is suffering from severe cold, he or she cannot

(a) differentiate the taste of an apple from that of an ice cream

(b) differentiate the smell of a perfume from that of an agarbatti

(c) differentiate red light from green light

(d) differentiate a hot object from a cold object

Sol. (b)

---

Q.25 What is the correct direction of flow of electrical impulses?

Sol.  (c)

---

Q.26 Which statement is not true about thyroxin?

(a) Iron is essential for the synthesis of thyroxin

(b) It regulates carbohydrates, protein and fat metabolism in the body

(c) Thyroid gland requires iodine to synthesise thyroxin

(d) Thyroxin is also called thyroid hormone

Sol. (a)

---

Q.27 Dwarfism results due to

(a) Excess secretion of thyroxin

(b) Less secretion of growth hormone

(c) Less secretion of adrenaline

(d) Excess secretion of growth hormone

Sol. (b)

---

Q.28 Dramatic changes of body features associated with puberty are mainly because of secretion of

(a) oestrogen from testes and testosterone from ovary

(b) estrogen from adrenal gland and testosterone from pituitary gland

(c) testosterone from testes and estrogen from ovary

(d) testosterone from thyroid gland and estrogen from pituitary gland

Sol. (c)

---

Q.29 A doctor advised a person to take an injection of insulin because

(a) his blood pressure was low

(b) his heart was beating slowly

(c) he was suffering from goitre

(d) his sugar level in blood was high

Sol. (d)

---

Q.30 The hormone which increases the fertility in males is called

(a) oestrogen

(b) testosterone

(c) insulin

(d) growth hormone

Sol. (b)

---

Q.31 Which of the following endocrine glands is unpaired?

(a) Adrenal

(b) Testes

(c) Pituitary

(d) Ovary

Sol. (c)

---

Q.32 Junction between two neurons is called

(a) cell junction

(b) neuro muscular junction

(c) neural joint

(d) synapse

Sol. (d)

---

Q.33 In humans, the life processes are controlled and regulated by

(a) reproductive and endocrine systems

(b) respiratory and nervous systems

(c) endocrine and digestive systems

(d) nervous and endocrine systems

Sol. (d)