Question 1:
Which of
the following is a plant hormone?
(a) Insulin
(b) Thyroxin
(c) Oestrogen
(d) Cytokinin
(d) Cytokinin
is a plant hormone.
Question 2:
The gap
between two neurons is called a
(a) dendrite.
(b) synapse.
(c) axon.
(d) impulse.
(b) The
gap between two neurons is called a synapse.
Question 3:
The brain
is responsible for
(a) thinking.
(b) regulating
the heart beat.
(c) balancing
the body.
(d) all
of the above.
(d) The brain is
responsible for thinking, regulating the
heart beat and balancing the body.
Question 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?
Receptors
are sensory structures (organs/tissues or cells) present all over the
body. The receptors are either grouped in case of eye or ear, or
scattered in case of skin.
Functions
of receptors:
(i) They
sense the external stimuli such as heat or pain.
(ii) They also trigger an impulse in the sensory
neuron which sends message to the spinal
cord.
When the
receptors are damaged, the external stimuli transferring signals to
the brain are not felt. For example, in the case of damaged
receptors, if we accidentally touch any hot object, then our hands
might get burnt as damaged receptors cannot perceive the external
stimuli of heat and pain.
Question 5:
Draw the structure of a neuron and explain its function.
Neurons
are the functional units of the nervous
system. The three main parts of a neuron are axon, dendrite, and cell
body.
 |
Structure of a neuron
Question 6:
How does
phototropism occur in plants?
Thegrowth movement in plants in response
to light stimulus is known as phototropism.The shoots show positive phototropism
and the roots show negative phototropism. This means that the shoots
bend towards the source of light whereas the roots bend away from the
light source.
Some
examples of phototropism are as
follows:
(a) The flower head of sunflower is positively phototropic and hence
it moves from east to west along with the sun.
(b) The ovary stalk of groundnut is positively phototropic before
fertilization and becomes negatively phototropic after fertilization,
so that the fruit is formed underground.
Question 7:
Which
signals will get disrupted in case of a spinal cord injury?
The reflex
arc connections between the input and output nerves meet in a bundle
in the spinal cord. In fact, nerves from all over the body meet in a
bundle in the spinal cord on their way to the brain. In case of any
injury to the spinal cord, the signals coming from the nerves as well
as the signals coming to the receptors will be disrupted.
Question 8:
How does chemical coordination occur in plants?
In
animals, control and coordination occur with the help of nervous
system. However, plants do not have a nervous system.
Plants
respond to stimuli by showing movements. The growth, development, and
responses to the environment in plants is controlled and coordinated
by a special class of chemical substances known as hormones. These
hormones are produced in one part of the plant body and are
translocated to other needy parts. For example, a hormone produced in
roots is translocated to other parts when required. The five major
types of phytohormone are auxins, gibberellins, cytokinins, abscisic
acid, and ethylene. These phytohormones are either growth promoters
(such as auxins, gibberellins, cytokinins, and ethylene) or growth
inhibitors such as abscisic acid.
Question 9:
What is the need for a system of control and coordination in an
organism?
The
maintenance of the body functions in response to changes in the body
by working together of various integrated body systems is known as
coordination. All the movements that occur in response to stimuli are
carefully coordinated and controlled. In animals, the control and
coordination movements are provided by nervous and muscular systems.
The nervous system sends messages to and away from the brain. The
spinal cord plays an important role in the relay of messages. In the
absence of this system of control and coordination, our body will not
be able to function properly. For example, when we accidentally touch
a hot utensil, we immediately withdraw our hand. In the absence of
nerve transmission, we will not withdraw our hand and may get burnt.
Question 10:
How are involuntary actions and reflex actions different from each
other?
Involuntary
actions cannot be consciously controlled. For example, we cannot
consciously control the movement of food in the alimentary canal.
These actions are however directly under the control of the brain. On
the other hand, the reflex actions such as closing of eyes
immediately when bright light is focused show sudden response and do
not involve any thinking. This means that unlike involuntary actions,
the reflex actions are not under the control of brain.
Question 11:
Compare
and contrast nervous and hormonal mechanisms for control and
coordination in animals.
| Nervous system mechanism | Hormonal system mechanism | ||
| 1. | The information is conveyed in the form of electric impulse. | 1. | The information is conveyed in the form of chemical messengers. |
| 2. | The axons and dendrites transmit the information through a coordinated effort. | 2. | The information is transmitted or transported through blood. |
| 3. | The flow of information is rapid and the response is quick. | 3. | The information travels slowly and the response is slow. |
| 4. | Its effects are short lived. | 4. | It has prolonged effects. |
Question 12:
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 plants | Movement in our legs | ||
| 1. | The movementthat takes place in a sensitive plant such as Mimosa pudica occurs in response to touch (stimulus). | 1. | Movement in our legs is an example of voluntary actions. |
| 2. | For this movement, the information is transmitted from cell to cell by electro-chemical signals as plants do not have any specialised tissue for conduction of impulses. | 2. | The signal or messages for these actions are passed to the brain and hence are consciously controlled. |
| 3. | For this movement to occur, the plant cells change shape by changing the amount of water in them. | 3. | In animal muscle cells, some proteins are found which allow the movement to occur. |