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BALAJI
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Control & Coordination
Very Short Answer
Q. 1. List two body functions that will be affected if cerebellum
gets damaged.
[CBSE, Term 1, Set 1, 2016]
Ans. Two body functions that will be affected if
cerebellum gets damaged are equilibrium and
posture.
Q. 2. Name one plant hormone which inhibits growth. Write its
one more function.
[CBSE, Term 1, Set 2, 2015]
Ans. Abscisic acid is a plant hormone whichfunctions
mainly as a growth inhibitor.
(i) It promotes the dormancy in seedsand buds.
(ii) It promotes the closing of stomata.
(iii) It promotes the wilting and falling ofleaves.
Short Answer
Q. 1. List two different functions performed by pancreas in our
body.
[CBSE Delhi, Set 3, 2019]
Ans. (i) Pancreas makes two hormones i.e., insulin and
glucagon that regulates blood sugar level.
(ii) It secretes pancreatic juice which contains
enzymes that aids in the digestion of food.
Q. 2. (a) Name one gustatory receptor and one olfactory
receptor present in human beings.
(b) Write a and b in the given flow chart of neuron
through which information travels as an electrical
impulse.
Ans. (a) Tongue is the gustatory receptorpresent in
the human body.
(b) Dendrite Cell body Axon Endpoint of
Neuron
Q. 3. Name the plant hormones responsiblefor the following
functions:
(i) growth of the stem
(ii) promotes cell division
(iii) wilting of leaves
(iv) inhibits growth
[CBSE, Term 1, Set 1, 2015]
Ans.
Function Hormone responsible
(i) Growth of the stem Auxin or Gibberellin
[CBSE, 2018]
(ii) Promotes cell division Cytokinin
(iii) Wilting of leaves Abscisic acid
(iv) Inhibits growth Abscisic acid
Short Answer
Q. 1. A squirrel is in a scary situation. Its bodyhas to prepare for
either fighting or running away. State the immediate
changesthat take place in its body so that the squirrel
is able to either fight or run?
[CBSE Delhi, Set 1, 2020]
Ans. The squirrel body is relied only on electrical
impulses via nerve cells, the range of tissues
instructed to prepare for the coming activity
would be limited. Onthe other hand, if a chemical
signal were
to be sent as well, it would reach all cells of the
body and provide the wide range of changes
needed. This is done using a hormone called
adrenaline that is secreted from the adrenal
glands.
Q. 2. Why is chemical communication better than electrical
impulses as a means of communication between cells
in a multi-cellular organism?
[CBSE Delhi, Set 1, 2020]
End point of Neuron
Dendrite
BALAJI
Ans. Chemical coordination is better than electrical
impulses as a means of communication between
the cells in a multi- cellular organism because in
animals, the messages are communicated in the
form of nerve impulses quickly. But still, there
aresome limitations to the nervous system. Nerve
impulses can reach only those cells which are
connected by the nervous tis- sues and the cells
connected by nervous tissues, after generation
and transmission of the impulse, take some time
to restbefore the generation and transmission of
new impulse. In simple words, cells can- not
continuously generate and transmit nerve
impulses. This is the reason why most
multicellular organisms use another form of
control and coordination, named chemical
coordination. The advantage of chemical
coordination is that the information spreads out
throughout the body by blood (then the required
part picks it up as per its requirement) and the
effect generally lasts longer.
Q. 3. Name the parts (a) to (e) in the followingdiagram.
What is the term given to the sequenceof events
occurring in the diagram?
[CBSE Delhi, Set 3, 2020]
Ans. (a) Receptors
(b) Sensory neuron
(c) Spinal cord (CNS)
(d) Relay neuron
(e) Motor neuron
Reflex arc is the term given to the sequenceof
events occurring in the diagram.
Q. 4. (a) What is tropism?
(b) How do auxins promote the growthof a tendril
around a support?
[CBSE Delhi, Set 3, 2020]
Ans. (a) When the direction of external stimulus decides
the direction of response in the form of
growth it is called tropism. Thus, tropism is
the directional growth movement of a plant
part. It can be in the direction of the stimulus
or away from the stimulus.
(b) Auxin is a plant growth hormone which is
synthesized at the tip of the shoot. It helps the
cell grow longer. When a tendril comes in
contact with a support, auxins stimulates
faster growth of the cells on the oppositeside
that’s why the tendril forms acoil around the
support and in this way auxins promote the
growth of thetendril around a support.
Q. 5. Trace the sequence of events which occurwhen a bright
light is focused on your eyes. [CBSE Delhi, Set
1, 2019]
Ans. When bright light is focussed on our eyes it goes to
brain, the brain reverts back themessage by motor
neuron which con- tracts the pupil. The sequence
of events which occur is as follows:
Receptor Sensory neuron Brain
Pupil contraction Eye muscles Motor
neurons
Q. 6. What are plant hormones? Name the plant hormones
responsible for the following:
(i) Growth of stem
(ii) Promotion of cell division
(iii) Inhibition of growth
(iv) Elongation of cells
[CBSE Delhi, Set 1, 2019]
Ans. In plants, growth, development and response to the
environment arecontrolled and coordinated by a
special class of chemical substances known as
phytohormones. They are synthesised in minute
amounts.
(i) Gibberellins (ii) Cytokinins
(iii) Abscisic acid (iv) Auxins
BALAJI
Topper’s Answers
Ans. (a) Thyroid gland secretes thyroxine. It regulates the
metabolism and blood pressure of human beings.
(b) Pituitary secretes growth hormone. It helps the
bones and other body organsto grow properly.
Root grows
towards
water
Water
B
Clay
pot
(c) Pancreas secretes insulin. Insulin
helps to lower blood sugar level.
Dry soil
(b) Moist soil
Q. 11. Design an experiment to demonstratehydrotropism.
[CBSE, Term 1, Set 1, 2016]
Ans. Experiment to demonstrate hydrotropismin Plants:
(b) In absence of water
Q. 12. Draw a diagram showing the correct positions of pancreas,
thyroid gland, pituitary gland, Adrenal gland in humanbeing.
[CBSE, Term 1, Set 1, 2016]
[CBSE, Term 1, Set 1, 2015]
Ans.
A
Root
Pituitary gland
Thyroid gland
grows
straight
Adrenal glands
Pancreas
Moist soil Moist
soil(a)
(a) In presence of water
BALAJI
Q. 13. State the function of receptors in ourbody. Think of any
three situations where receptors in the body do not
workproperly. Mention the problems which are likely
to arise.
[CBSE, Term 1, Set 2, 2015]
Ans. A receptor is a cell (or a group of cells) in a sense
organ which is sensitive to a particular type of
stimulus such as light, sound, smell, taste, heat,
pressure, etc. The different sense organs contain
receptors for detecting different stimuli.
When receptors do not work properly, the
environmental stimuli are not able to create nerve
impulses and the body does not responds.
When receptors are damaged, the externalstimuli
transferring signals to the brain are not felt.
For example,
(i) During fever, taste buds do not work properly
and as a result, taste of the food eaten is not felt
properly. Thus, enzyme secretion is also
affected.
(ii) When a person is suffering from a cold, the
nostrils are filled with
mucus. Then smell of the surroundingis not
felt properly. This is due to interruption in
reacting to the sense ofsmell by the olfactory
receptor.
(iii) When skin receptors are damaged, and we
accidentally touch a hot object,then our hands
might get burnt as the damaged receptor
cannot perceive the external stimuli of heat
and pain.
Q. 14. Name any three glands associated with digestion in
humans. Write the names of enzymes secreted by
them.
[CBSE Delhi, Term 1, Set 1, 2015]
Ans. Salivary glands, Pancreas and gastric glands are
associated with digestion inhumans.
S. No. Glands Enzymes
Salivary glands Salivary amylase
Pancreas Pancreatic amylase
Trypsin
Lipase
Gastric glands Pepsin
Long Answer
Q. 1. (a) Why is the use of iodised salt advisable? Name the
disease caused due to deficiency of iodine in ourdiet and state
its one symptom.
(b) How do nerve impulses travel in the body?
Explain.
[CBSE OD, Set 1, 2019]
Ans. (a) Iodised salt is advisable because iodine is
necessary for the formation of thyroxine
hormone by thyroid gland. Goitre is the
disease caused due to its deficiency.
Symptom: The neck of the person appears to
be swollen due to the enlargement of thyroid
gland.
(b) Two neurons are not joined to one another
completely. There is a small gap between a
pair of neuron. This gap is called synapse.
The nerveimpulse are carried out to this gap
by the help of neuro-transmitter
(chemical substance). The conduction of
nerve impulse through the synapse takes
place in the form of electrical nerve impulse.
When a stimulus acts on the receptor, an
electrical impulse is produced with the help
of chemical reaction. This electrical impulse
passes through the synapse and then to the
other neuron. Thus, in this way nerve
impulses travel in the body.
Q. 2. What is hydrotropism? Design an experi- ment to
demonstrate this phenomenon.
[CBSE OD, Set 1, 2019]
Ans. The movement of root of plants towards water is
called hydrotropism.
Take two glass troughs A and B. Fill each one of
them two-third with soil. In trough A plant a tiny
seedling (figure (a)). In trough B plant a similar
seedling and also a small ‘clay pot’ is placed
inside the soil (figure (b)). Water the soil in trough
A daily and uniformly. Do not water the soil in trough B but put some waterin the clay pot buried in the soil.
Leave both the troughs for a few days.
Now, dig up the seedlings carefully fromboth the trough without damaging their roots. We will find that the
root of seedlingin trough A is straight. On the other hand,the root of seedling in trough B is found tobe bent to
BALAJI
Reflex actions are the actions which weperform without thinking to protect ourselves. For example, coughing is a
reflex action which clears our windpipe.The pupils of our eyes get smaller in bright light. This reflex action protects
the retina of our eyes from damage dueto much light. The pupils of our eyes gets bigger in dim light so as to help
ussee properly even in dim light.
(b) Plants respond to external stimuli such as light, touch, etc. A growth movement of a plant part in response to an
external stimulus in which the direction of stimuli determines the direction of response is called tropism.
(i) If the growth of a plant part is towards the stimuli, it is calledpositive tropism.
(ii) If the growth of a plant part is away from the stimulus, then it is called negative tropism.
Types of tropism:
(i) The movement of a plant part in response to light is called phototropism.
(ii) The movement of a plant part in response to gravity is called geotropism.
(iii) The movement of a plant part in response to chemicals is called chemotropism.
(iv) The movement of a plant part in response to water is called hydro-tropism.
(v) The directional growth movement of a plant part in response to the touch of an object is called thigmotropism.
Nasties (or Nastic Movements). The movement of a plant part in response to an external stimulus in which the
direction of response is not deter-mined by the direction of stimulus iscalled nastic movement.
(vi) The folding up of the leaves of a sensitive plant on touching is an example of nastic movement. Here the stimulus is
touch.
(vii) The opening up of the petals of dandelion flowers in morning in bright light and closing in the evening when
the light fades is an example of nastic movement. In this case the stimulus is light.
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