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Science · 2024 · 5 marks
CBSE 2024 · Region 4 · Set 1 · Q35
(a) (i) Define a reflex arc. Why have reflex arcs evolved in animals? Trace the sequence of events which occur, when you suddenly touch a hot object.…
(i)
Define a reflex arc. Why have reflex arcs evolved in animals ? Trace the sequence of events which occur, when you suddenly touch a hot object.
(ii)
Name the part of nervous system which helps in communication between the central nervous system and other parts of the body. What are the two components of this system ?
(i)
Leaves of 'chhui-mui' plant begin to fold up and droop in response to a stimulus. Name the stimulus and write the cause for such a rapid movement. Is there any growth involved in the movement ?
(ii)
Define geotropism in plants. What is meant by positive and negative geotropism ? Give one example of each type.
Marking-scheme solution
(i) • The pathway in which impulses travel during the reflex action is called a reflex arc.
Because the thinking part of the brain is not fast enough/for quick response to avoid injury.
Reflex arc :
(ii) Peripheral Nervous System Components : Cranial Nerves; Spinal Nerves
OR
(i) •Touch
The shape of the leaves changes by changing the amount of water in them.
No
(ii) Growth of a part of plant in response to the pull of earth or gravity is called geotropism.
Positive geotropism - Movement of plant part towards the earth gravity. Example - Roots grow downwards
Negative geotropism - Movement of plant part away from the force of gravity. Example - Shoots grow upwards.
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CBSE Class 10 Science past-paper question from the 2024 board exam, with the answer as CBSE’s own marking scheme gives it. Where our answers come from.