Control and coordination
Question. Mention three important functions of gibberellins.
Ans. Functions of Gibberllins –
(i) Stimulate stem elongation.
(ii) Help in breaking seed dormancy.
(iii) Promote flowering in some plants even under unfavorable conditions
(iv) Help in seed germination.
(v) Promote production of male flowers.
Question. What is the function of receptors in our body? What happens when receptors do not work properly?
Ans. The function of receptors is to defect information form the environment. If receptors do not work properly, the information
obtained form the environment will be delayed to reach the spinal cord or brain. In this situation, the response to the environmental
stimulus will be delayed causing harm to the body.
Question. What happens at the synapse between two neurons?
Ans. The nerve impulse gets transmitted through the synapse by means of chemical signals. When a stimulus acts on the receptor,
chemical reaction is set off which produces an impulse in it. This impulse travels form the dendrite of presynaptic neuron to its cell
body and then along its axon. At the end of axon of this neuron, the electrical impulse releases tiny amount of a chemical
substance crosses the synapse and starts a similar electrical impulse in the dendrite of the next neuron.
Question. What is the need for a system of control and co – ordination in an organism?
Ans. a) It evokes an appropriate movement in response to any change in external environment
b) Multicellular organisms have complex body. So it, co – ordinates various organs of body of an organism work together in a
proper manner to produce proper reaction to stimulus
Question. Pituitary is a master endocrine gland. Justify this statement.
Ans. Pituitary gland is also known as master gland because it controls the activities of most of the gland.
It regulates the secretion of other glands. Likea) Growth hormones – Body growth and development of bones
b) Thyroid stimulating hormone – Secretion of hormones form thyroid gland.
c) Adrenocorticotropic hormone – Secretion of hormones form adrenal glands.
d) Follicle stimulating hormone – Stimulating of growth of ovaries and testes
e) Luteinsing hormone – Secretion of hormone from ovaries & testes
f) prolactin – Regulation of function of mammary gland. Hence, most of functions are controlled by pituitary gland so it is called
master gland.
Question. Draw the structure of neuron and explain its function.
Ans. Neuron has three components – (i) Cell body (ii) Dendrites (iii) Axon
The dendrite picks up the nerve impulse from receptors and then pass the impulses to the cell body and then along the axon. The
axon passes the impulse to another neuron through a junction called synapse.
Question. Define ‘nerve impulse’. Which structure in a neuron helps to conduct a nerve impulse?
a) Towards the cell body?
b) Away from the cell body?
Ans. Nerve Impulse – It is the passing of information through neurons is in the form of electrical and chemical signals. This is
called nerve impulse.
a) Dendrite b) Axon
Question. What are tropic movements? Name the types of tropic movements in plants.
Ans. The bending or movement of a part of plant in response to the external stimulus is called tropism or tropical movement. It is
of following types.
(a) Phototropism – It is response to light. It may be towards light (positive) or away from the light (negative).
(b) Geotropism – It is response to gravity – It may be towards stimulus (positive) and away from the stimulus (negative)
(c) Chemotropism – Response to chemicals. It may be positive or negative.
(d) Hydrotropism – Response to water. It may be positive or negative.
Question. How do auxins promote the growth of tendril around a support?
Ans. When the tip of a tendril touches a support, then the auxins present in its tip move to that side of tip which is away form the
support, auxins promote growth. So, due to more auxins in it, the side of tendril, away from the support, grow faster and becomes
longer than the side which is in contact with the support and makes the tendril curve towards the support.
Question. What are the different kinds of neurons?
Ans. Kinds of neurons –
a) Sensory neurons – convey impulses from receptors to the main nervous system.
b) Motor neurons – carry impulses from the main nervous system to an effector.
c) Connecting/ associations (Relay) neurons – connect sensory and motor centres.
Question. Differentiate between axon and dendrons?
Answer
Question. Design an experiment to demonstrate hydrotropism.
Ans. Take a tin box with hole at bottom. Fill it with moist saw dust. Sow some gram seeds in it. Keep the tin box in tilted position.
When seeds start germinating, water the saw dust only in lower side of the tin box. You will observe that the radicle move towards
the wet saw dust. This shows that root is positively hydrotropic.
Question. A man becomes unconscious due to head injury. A pin is pricked on his foot, he withdraws his foot. Why? Explain.
Ans. It is reflex action. Stimulus is perceived by receptor (skin). Sensory nerve sends the sensation from receptor to the spinal cord.
Then spinal cord sends the message through motor nerves to the effectors. Effectors i.e. muscles help in withdrawing his foot.
Question. How does the plant shoot bends, when the plant is placed in a room having only one open window?
Ans. When the plant is placed in such a room that has only one open window, the shoot of the plant bends towards the direction of
light. Plant hormone axing is formed that diffuses towards the shady side of the shoot and stimulates the cells to live longer on the
side of the shoot which is away from light. In this way the shoot bends towards the light.
Question. On touching a hot plate, you suddenly withdraw your hand. Which category of neurons became active first and which
one next?
Ans. On touching a hot plate, first the sensory neurons are activated, which take the information to the brain or the spinal cord.
Next, the motor neurons become active and bring the impulses from the brain to the muscles. In receiving these impulses, the
muscles contract, and the hand is immediately removed from the hot plate.
Question. What is the difference between the manner in which movement takes place in a sensitive plant and the movement in
our legs?
Movement in sensitive plant
Movement in legs
The movement is a sensitive response to stimulus(touch)
Movement in our legs is a voluntary action.
No special tissue is there for the transfer of information A complete system CNS and PNS is there for the information exchange.
Plant cells do not have specialised protein for movements
Animal cells have specialised protein, which helps muscles to
contract.
Plant hormones control it.
The cerebellum of the hindbrain controls it.
Question. What are plant hormones?
Ans. Plant hormones are chemicals present in plants which help to coordinate growth, development and responses to stimuli and
environment. For example, auxins, gibberellins, cytolcinins, abscisic acids are different plant hormones.
Question. How is the movement of leaves of the sensitive plant different from the movement of a shoot towards light?
Ans. The movement of leaves of a sensitive plant is neither towards, nor away from the stimulus touch; it is a non-directional
movement (nastic movement) while movement of shoot is towards the stimulus like light; it is a directional movement (tropic
movement).
Question. Give an example of a plant hormone that promotes growth.
Ans. Auxin is the plant hormone that helps in cell growth and elongation. Gibberellins promote growth of stem.
Question. How do auxins promote the growth of a tendril around a support?
Ans. When tendrils 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 is caused by the action of auxin hormone. Less auxin occurs on the side of
contact as compared to the free side. As a result, auxin promotes growth on the free side and the tendrils coil around the support.
Question. Design an experiment to demonstrate hydrotropism.
Ans. Hydrotropism is the process of growth or movement of roots towards the source of water. Here is an experiment that is
performed to observe the growth of plants when water is present.
Procedure :
Take two beakers 1 and 2.
In beaker 1 add moist soil and sow the seeds.
In beaker 2 add dry soil in one part and moist soil in another part and sow the seeds. Also, place a small beaker of water just
adjacent to it.
Keep it for some time so that the plants can grow.
Result
It was found that in beaker 1 due to the presence of moist soil, plants will grow normally and roots will be straight.
In beaker 2 it was observed that the presence of water beaker next to its plant grows towards the water as shown in the above
figure.
Conclusion
This experiment states that the plants move and grows towards the source of water, hence plants show hydrotropism.
Question. Which of the following is the plant hormone?
(a) Insulin
(b) Thyroxine
(c) Oestrogen
(d) Cytokinin
Ans. (d) Cytokinin
Question. The gap between two neurons is called a
(a) dendrite
(b) synapse
(c) axon
(d) impulse
Ans. (b) synapse.
Question. The brain is responsible for
(a) thinking.
(b) regulating the heart beat.
(c) balancing the body. (d) all of the above.
Ans. (d) all of the above.
Question. What is the function of receptors in our body? Think of situations where receptors do not work properly. What
problems are likely to arise?
Ans. The receptors in our body collect information about changes in the environment around us in the form of stimuli. They are
located in our sense organs such as the inner ear, nose, tongue, eye, etc.
These then pass the information in the form of nerve impulses to central nervous system (spinal cord and brain) where
message is interpreted and instructions are sent to effectors which reveal responses.
When receptors do not work properly, the environmental stimuli are not able to create nerve impulses and body does not
respond.
Question. Draw the structure of a neuron and explain its function.
Ans. Neuron
Functions: The information acquired at the end of the dendritic tip of a neuron sets off a chemical reaction which creates an
electrical impulse. This impulse travels from the dendrite to the cell body, and then along the on to its end. At the end of on, the
electrical impulse sets off the release of some chemicals, which cross the synapse and start a similar impulse in a dendrite of the
next neuron.
In this way nervous impulses travel in the body. Thus, nervous tissue is made up of an organized network of neurons which are
specialized for conducting information via electrical impulse from one part of the body to another.
Question. How does phototropism occur in plants?
Ans. Phototropism is the growth of plant parts in response to a light stimulus. During phototropism, the cells on the plant that are
farthest from the light contain a chemical called auxin reacts, which causes the plant to have elongated cells on the furthest side
from the light. Hence, shows the growth and movement toward light.
An example of phototropism is plant stem growth in the direction of sunlight (upward).
[Extra information: The movement or growth of plant parts towards the light source is known as positive phototropism, whereas
the movement or growth of plant parts away from light is known as negative phototropism.
Example- Positive Phototropism - Stems (grow upwards), Negative Phototropism - Roots (grow downwards). In a plant, stem (or
shoot) shows positive phototropism, as it grows towards the sunlight.]
Question. What is the need for a system of control and coordination in an organism?
Ans. The body of a multicellular organism consists of a number of components and sub-components and each is specialized to
perform a particular function. Therefore, it is necessary that various organs of the body of an organism work together in a proper
manner for proper functioning to a stimulus. In human beings nervous system and endocrine system work together to control and
coordination.
Question. What is the difference between the manner in which movement takes place in a sensitive plant and movement in our
legs?
Ans. Movement in a sensitive plant
(i) It occurs in response to an external stimulus like touch and shock.
(ii) Plant cells change shape by changing the amount of water.
(iii) No nerves are involved.
(iv) There is no specialized tissue in plants for conduction of information.
(v) Plant cells do not have specialized proteins.
Movement in our legs
(i) It occurs in response to our requirements and is a voluntary action.
(ii) Movement in our legs is voluntary action which is controlled by cerebellum part of hind brain.
(iiip) Nerves carry the message for movement of legs.
(iv) There is specialized nervous tissue in animals for conduction of information and muscle cells to help in movement.
(v) Animal cells have specialized protein which help muscles to contract or relax.
Question. Mention the receptors for light and sound in animals.
Answer: Sense organs are called receptors. The receptor of light in animals is calld photoreceptor. The receptor of sound in
animals is called phonoreceptor.
Question . Define ‘reflex action.’
Answer: Reflex action is a rapid, automatic response to a stimulus which is not under the voluntary control of the brain
Question . What is an axon?
Answer: It is a large, single, unbranched nerve fibre arising from the cyton. It carries impulses from cyton located in CNS to
effectors.
Question . Why are roots called positively geotropic?
Answer: This is because the roots always grow towards the gravity of the Earth.
Question . Name the largest cell present in the human body.
Answer:
Question .Which part of central nervous system controls reflexes?
Answer: Spinal cord.
Question . Name the part of neuron.
(i) Where information is acquired.
(ii) Through which information travels as an electrical impulse.
Answer: (i) Dendrite,
(ii) Axon.
Question .Name two tissues that provide control and coordination in multicellular animals.
Answer:The two tissues that provide control and coordination in multicellular animals are nervous tissue and muscular tissue.
Question .What do you understand by the sleep movement of plant organs?
Answer: Sleep movement in plants e.g., in flowers is to protect the reproductive organs from the cold. Hence, sepals and petals of
saffron flower close at sunset and open up in the morning.
Question . State the main function of abscistic acid in plants. Answer: Abscisic acid slows plant growth and inhibits division of
cells.’ Question 18. What is spinal cord? Which body function is controlled by it?
Answer: Spinal cord is a long and cylindrical tube which is present in vertebral column. From its dorsal and ventral horn sensory
and motor nerves originate which form spinal nerve. At the centre it contains neurocoel. Spinal cord is covered externally by three
membranes. In this, H shaped grey matter is filled, which is surrounded by white matter. Lateral and dorsal sides have horns.
Spinal cord: It serves as principal centre for almost all the reflexes and involuntary activities. It provide conduction pathway for
nerves to transmit stimuli to brain.
Question .Define a synapse.
Answer: Synapse is a very fine gap between telodendria of axon of one neuron and dendrites of another neuron. These two
structures do not unite with each other but remain separated by a fine gap.
Question . Why Mimosa pudica (touch-me-not) leaves droop down when touched?
Answer: It is due to turgor pressure difference between the upper and lower halves of the base of petiole (pulvinus). Lower half
cells lose water and upper half cells of pulvinus become turgid due to transfer of water from lower cells. Thus, the entire leaf
droops down when touched.
Question . Why are the electrical-chemical signals not an efficient means of communication in plants?
Answer: Unlike animals, where there is a nervous system for conduction of nerve impulses and circulatory system for conduction
of hormones, there are no specialised tissues in plants. So, the electrical chemical signals are not an effective means of
communication in plants.
Question . If a ripened fruit is kept in a basket of raw fruits, then what will happen? What causes it?
Answer: The ripened fruit will release ethylene (hormone) which causes ripening of other raw. fruits kept in a basket.
Question . What is turgor movement?
Answer: Turgor movement is the movement due to the difference of turgidity of the cells in the lower half and upper half of
pulvinus (petiole of leaf). When leaf of touch-me-not plant (Mimosa pudica) is touched, the electrical signal send chemical signals
from leaflets to pulvinus (petiole) of leaf. Cells in the lower half of pulvinus lose water and become flaccid, while cells in the upper
half of pulvinus become turgid due to accumulation of more water. Hence, leaf droops down for a short time.
Question . Why do tendrils coil around hard rough objects?
Answer: The growth movement of tendril in response to unilateral stimulus of touch is called thigmotropism. Tendrils of louki, tori,
karela, and sweet pea plants coil around hard objects when they come in their contact. It occurs due to unequal growth of two
sides of a tendril. The growth of the surface which comes in contact of the support is retarded, while it remains normal or
increased on the other side, due to which tendril coils around the support.
Question. Write the difference between tropism and nastic movement.
Answer: Tropisms movement and nastic movements are both plants in response to external stimuli, but tropisms are relying on the
path of the stimulus nastic movements do not rely on the path of a stimulus.
Question . Difference between the tropism movement and the nastic movement
The difference between the tropism movement and the nastic movement are tabulated below.
Tropism movement
1.The response to stimuli that arrive from
Nastic movement
1. Nastic gestures are non-directional responses
one direction is tropical movement.
to stimuli including heat and temperature.
2.It is a motion that is directional.
2. The most significant characteristic of this form
of movement is that the direction of the
stimulus does not control movements.
3.If the plant component’s movement is
3. If the plant portion’s movement is away from
towards the stimulus, it is referred to as
the stimulus, it is referred to as negative tropism.
positive tropism.
Touching, temperature, light, and chemicals may
induce them.
4.Examples – Geotropism, Phototropism etc.
4. Examples – The movement of the Venus
flytrap is an instance of seismonastic
movement.
Question: the various functions performed by the plant hormones.
Or
Name various plant hormones. Also give their physiological effects on plant growth and development.
Answer:The various functions performed by the plant hormones are:
(i) Auxins promote cell enlargement and cell differentiation. They also promote growth.
(ii) Gibberellins promote cell enlargement and cell differentiation in the presence of auxin. It also help in breaking the dormancy in
seeds and buds. It promote the growth in fruits.
(iii) Cytokinins promote cell division and help in breaking the dormancy of seeds and buds. It delay the ageing in leaves. It promotes
the opening of stomata and also fruit growth.
(iv) Abscisic acid promotes the dormancy in seeds and buds. It promotes the closing of stomata and falling of leaves. It also
inhibits growth, reverses the growth promoting effects of auxins and gibberellins. Its effects include wilting of leaves.
(v) Ethylene promotes the falling of leaves, ripening of fruits and helps in breaking bud dormancy.
Question . Name the receptors that help to detect (i) taste and (ii) smell.
Answer: (i) Gustatory receptors help to detect taste.
(ii) Olfactory receptors help to detect smell.
Q. What do we call the gap present between two neurons?
Answer: Synapse
Q. Which part of the brain controls involuntary actions?
Answer: Involuntary actions are controlled by the medulla in the hind-brain.
Q. Which part of the brain controls voluntary actions?
Answer: Involuntary actions are controlled by the cerebellum in the hind-brain.
Q. Which plant hormone is responsible for the wilting of leaves?
Answer: Abscisic acid
Q. Why do the plant shoots bend towards light?
Answer: The bending of plant shoots towards light is termed as phototropism. It is due to the plant hormone called auxins. When
light falls on one side of the plant, the auxins generally spread towards the darker side of the shoot. This stimulates the cells in the
darker side to grow longer than the corresponding cells of the illuminated region. This results in more growth on the darker side
which causes the stem to bend towards light.
Questions ; What are the main components of the reflex action?
Answer:
There are five main components of the reflex action that are:
(i) Receptors - Receive the message from the external environment.
(ii) Sensory neuron - carries the message from the receptor to the central nervous system.
(iii) Central nervous system - Processes the message and sends impulses to the concerned part of the body in the form of
response.
(iv) Motor neuron - Carries the message from the central nervous system to the effector.
(v) Effector - Includes muscles and glands that respond against the stimulus.
Plant hormones
So how do plants sense these changes in their environment!?
They do so with the help of hormones.
In this chapter, two types of hormones have been dealt with – growth promoters and growth inhibitors. These are:
Growth promoters – Auxins , Gibberellins , Cytokinins
Growth inhibitor – Abscisic acid
You can see major functions and significance of each of these hormones on your screen now.
Auxins –Promote cell enlargement, cell differentiation and fruit growth
Responsible for phototropic and geotropic responses of the plant
It speeds up growth in stem but slows down growth in roots
It is synthesized at the shoot tip
Gibberellins –
Promotes growth in presence of auxins
Stimulates elongation of shoots
Cytokinins –
Promote cell division
Present in greater concentration in fruits and seeds
Abscisic acid –
Promotes dormancy in seeds and buds
Also promotes closing of stomata
Promotes wilting and falling of leaves
Question . Why is control and coordination system necessary in organisms?
Answer All organisms have mechanisms to control their functions. However, in higher organisms the system required is more
complex as the individual is a complex multicellular organism with the parts separated by greater distance.
Question What is homeostasis?
Answer Homeostasis comes from two words- ‘homeo’ meaning same and ‘stasis’ meaning steady state within the body
Question . Give examples of some of the movements shown by plants
Answer ovements as in animals is absent in plants except in cases of sperm cells of ferns and mosses swimming towards the egg.
In plants, movement is association with the growth of the plants. For example, the shoot system moves towards sunlight and the
root system towards earth.
Question. What are growth regulators?
Answer Growth regulators are the chemicals that either promote or inhibit growth of the plants, their development and their
responses to the environment. They are also called the phytohormones.
Question . What are the stages of growth in plants?
Answer Growth in plants has three stages: Cell division, Cell enlargement, Cell differentiation.
Question . Name the different phytohormones.
Answer The different phytohormones are auxins, gibberellins, cytokinins, ethylene and abscissic acid.
Question . What are auxins?
Answer nAuxins are phytohormones that are concerned with shoot and root elongation, maintaining dormancy and apical
dominance.
Question . Give four major functions of auxins.
Answer Four major functions of auxins are:
Elongation of stem and root: In high concentrations it causes stem elongation ad in low concentration, it causes root elongation.
Apical dominance: As long as the apical buds produce auxins, the lateral buds are not allowed to grow.
Prevention of abscission: As long as the leaves and fruits produce auxin, they remain attached to the plant. If they stop producing
auxins, they fall.
Parthenocarpy: Auxins induce the ovaries to produce fruits without fertilization and this is called Parthenocarpy. It results in
seedless fruits. For example, papaya, orange, etc.
Question . What are gibberellins and where are they synthesized?
Answer Gibberellins are plants hormones that are mainly responsible for cell elongation. They are synthesized in embryos, young
leaves, root tips, buds and seeds.
Question . What is the most important commercial application of gibberellins?
Answer GA-3 (gibberellic acid), a gibberellin that has been studied the most, causes the barley seeds to produce the starchdigesting enzymes like maltase, amylase. This process is called malting. It is used in the brewing industry.
Question . What are cytokinins? Give an example.
Answer They are phytohormones that induce cell division even in mature tissues. They were named ‘cytokinins’ as the cell division
is also called cytokinesis. For example: zeatin, a cytokinin present in maize grains.
Question . Give one use of cytokinins in tissue culture.
Answer Cytokinins are used in tissue culture to induce cell division in mature tissues.
Question 13 Name the phytohormone that causes ripening of fruits. Give one more function of this phytohormone.
Answer The growth regulator that causes ripening is ethylene. It also promotes flowering.
Question . Name a growth inhibitor. Give two o its functions.
Answer Abscisic acid is a growth inhibitor. Its functions are:
It causes bud and seed dormancy
It results in abscission of leaves and fruits
Question . With the help of an activity demonstrate geotropism in plants.
Answer:
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


Soak some seeds of gram or moong in water for one day.
Pierce slightly big holes (2 mm diameter) at the bottom of the cup.
Fill it with 1 cm. thick layer of garden soil.
Sprinkle soaked seeds (moong / gram) over the soil. Water the seeds.
Put the cup on 2 pieces of wooden or stone slabs so that there is a little gap between the top of the table and bottom of
the cup.


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Cover the lower part of the set-up with black paper.
Water the seeds regularly with little water.
You will observe that the roots come out from the holes and grow towards the Earth showing positive geotropism.
Question . What are nodes of Ranvier?
Answer : The nerve fibres may be enclosed within sheaths called ad myelin sheath. Along the fibres there are regions where the
myelin sheath is absent. These regions are called the nodes of anvier.
Question . What are hormones? What are the characteristics of hormones?
Answer : Hormones can be defined as secretions that are poured into blood in order to reach a specific target organ.
Hormones have the following characteristics:
i)They may be proteinaceous or non- proteinaceous (amino acids or steroids)
ii)They are secreted as per need and not stored, only excreted
iii)Their secretion may be regulated by nerves or by feedback effect
iv)They are transported by blood
v)They mostly cause long-term effects like growth, change in behavior, etc
vi)They do not catalyze any reactions
vii)They function by simulating or inhibiting the target organs.
Question . What are the functions of spinal cord?
Answer . The functions of the spinal cord are:
i)Coordinating simple spinal reflexes
ii)Coordinating autonomic reflexes like the contraction of the bladder
iii)Conducting messages from muscles and skin to the brain
iv)Conducting messages from brain to the trunk and limbs.
Question .What are receptors?
Answer: Receptors are structures at the ends of the nerve fibres that collect the information to be conducted by the nerves.
Question . What are effectors?
Answer : Effectors are muscles or glands which work in response to the stimulus received from the motor nerves.
Question . What are the three divisions of the human nervous system?
Answer : Human Nervous system can be divided into:
i)Central nervous system
ii)Peripheral nervous system
iii)Autonormic nervous system
Question . What is meningitis?
Answer. The brain and the spinal cord are protected by membranes called the meninges. An infection of the meninges is called
meningitis.
Question . Name the different region of the brain and their parts?
Answer , There are three main regions of the brain.
Fore brain - It is made up of cerebrum, hypothalamus and thalamus
Mid brain-It is relay center
Hind brain-It consists of cerebellum, pons and medulla oblongata
Question: Draw a well labelled diagram of Human Brain.
Answer:
Human Brain