1. Which of the following is a plant hormone?
(a) Insulin
(b) Thyroxin
(c) Oestrogen
(d) Cytokinin
Answer:
(d) Cytokinin
2. The gap between two neurons is called a
(a) dendrite
(b) synapse
(c) axon
(d) impulse
Answer:
(b) Synapse
3. The brain is responsible for
(a) thinking
(b) regulating the heartbeat
(c) balancing the body
(d) all of the above
Answer:
(b) All of
the above
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?
Answer:
The function
of receptors is to detect information from the environment. E.g., photoreceptors
in eye detect light.
If receptors
do not work properly, the information obtained from the environment will not
reach the CNS. As a result, the body cannot respond to the environmental stimuli.
It affects our abilities such as vision, hearing, smell, taste, touch etc.
5. Draw the structure of a neuron and explain its function.
Answer:
Function: Neurons carry information (electrical signals called
impulses) to and from the CNS.
6. How does phototropism occur in plants?
Answer:
Phototropism is the movement of a
plant part due to light. The shoot shows positive phototropism and roots show
negative phototropism.
Phototropism
occurs due to the hormone auxin. When light falls on one side of a plant, the
secretion of auxin hormone is more in the part away from the light. Hence,
auxin causes growth in length of the cells in shady part. So, the plant bends
towards light.
7. Which signals will get disrupted in case of a spinal cord
injury?
Answer:
· All the involuntary actions will be disrupted.
· Reflex actions will be disrupted.
· Signals to and from the brain will be disrupted.
8. How does chemical coordination occur in plants?
Answer:
Chemical
coordination in plants occurs with the help of plant hormones. In meristematic
regions, cells secrete hormones such as auxins. These substances identify the
information by stimulating the nearby cells and communicate the information.
9. What is the need for a system of control and coordination
in an organism?
Answer:
· To save the body of the organisms from the harmful changes
in the environment.
· To respond to external and internal stimuli.
· To control voluntary and involuntary actions.
10. How are involuntary actions and reflex actions different
from each other?
Answer:
Involuntary
action: It is a set of muscle
movements that do not require thinking. It is controlled by the brain. E.g.,
heartbeat.
Reflex
action: It is a rapid and spontaneous
response to a stimulus. It is controlled by spinal cord. E.g., sudden
withdrawal of hand when we touch a hot object.
11. Compare and contrast nervous and hormonal mechanisms for
control and coordination in animals.
Answer:
|
Nervous Mechanism |
Hormonal Mechanism |
|
It
involves neurons (nerve cells). |
It
involves endocrine glands. |
|
Signals
are transferred in the form of electrical impulses. |
Signals
are transferred in the form of chemicals (hormones). |
|
Impulses
travel quickly. |
Hormones
travel slowly. |
|
Quick
response. |
Slow
response. |
|
Signals
travel along the neurons. |
Signals
are transmitted through blood. |
|
The
effects are short-lived. |
The
effects are prolonged. |
12. What is the difference between the manner in which
movement takes place in a sensitive plant and the movement in our legs?
Answer:
|
Movement in a sensitive plant |
Movement in our legs |
|
Leaves
respond to touch (nastic movement). |
Leg
muscles respond to nerve impulses. |
|
It
is not controlled by any part of the plant. |
It
is controlled by brain and spinal cord. |
|
Here,
cells change their shape on changing the amount of water in them. |
Water
has no effect on the muscle movement. |