21.

Assertion : Pili are tubular structures present in bacteria which help in conjugation.

Reason : Formation of pili is controlled by F⁺  or fertility factor.

• If both assertion and reason are true and reason is the correct explanation of assertion.

• If both assertion and reason are true but reason is not the correct explanation of assertion.

• If assertion is true but reason is false

• If both assertion and reason are false

Assertion : In opposite phyllotaxy two leaves are borne on the opposite sides of a single node.

Reason : Opposite phyllotaxy is seen in China rose and Oleander.

• If both assertion and reason are true and reason is the correct explanation of assertion

• If both assertion and reason are true but reason is not the correct explanation of assertion

• If assertion is true but reason is false

• If both assertion and reason are false

Assertion : CAM plants lack structural compartmentation of leaf as found in C₄ plants.

Reason : Stomata of CAM plants are open during the day.

• If both assertion and reason are true and reason is the correct explanation of assertion

• If both assertion and reason are true but reason is not the correct explanation of assertion

• If assertion is true but reason is false

• If both assertion and reason are false

Assertion : Carbohydrates are more suitable for the production of energy in the body than proteins and fats.

Reason : Carbohydrates can be stored in the tissues as glycogen and can be used for the production of energy, whenever necessary.

• If both assertion and reason are true and reason is the correct explanation of assertion.

• If both assertion and reason are true but reason is not the correct explanation of assertion

• If assertion is true but reason is false

• If both assertion and reason are false

Assertion : Sphagnum is slowly carbonised, compressed and fossilised over thousands of years to produce a dark spongy mass called peat.

Reason : Peat helps to keep soil porous and it also improves water holding capacity of the soil.

• If both assertion and reason are true and reason is the correct explanation of assertion

• If both assertion and reason are true but reason is not the correct explanation of assertion

• If assertion is true but reason is false

• If both assertion and reason are false

Assertion : In Pleurobrachia, eight comb like ciliary plates called comb plates are present on the body that help in locomotion.

Reason : Pleurobrachia reproduces sexually and its life cycle includes cydippid larva.

• If both assertion and reason are true and reason is the correct explanation of assertion

• If both assertion and reason are true but reason is not the correct explanation of assertion

• If assertion is true but reason is false

• If both assertion and reason are false.

Assertion : Storage of seeds at low temperature is possible.

Reason : Respiration and anzymatic activity of seeds are very high at low temperature.

• If both assertion and reason are true and reason is the correct explanation of assertion

• If both assertion and reason are true but reason is not the correct explanation of assertion.

• If assertion is true but reason is false

• If both assertion and reason are false

Assertion : Presence of pneumatophores is a special adaptation of hydrophytes.

Reason : Pneumatophores are positively geotropic shoots that have lenticels and help in gaseous exchange.

• If both assertion and reason are true and reason is the correct explanation of assertion

• If both assertion and reason are true but reason is not the correct explanation of assertion

• If assertion is true but reason is false

• If both assertion and reason are false

Assertion : Atmospheric nitrogen gas is always fixed by nitrogen-fixing micro-organisms.

Reason : Decomposers release nitrogen gas from dead bodies of plants and animals.

• If both assertion and reason are true and reason is the correct explanation of assertion

• If both assertion and reason are true but reason is not the correct explanation of assertion

• If assertion is true but reason is false

• If both assertion and reason are false

Assertion : All motor neurons are efferent neurons.

Reason : Motor neurons conduct nerve impulses from the spinal cord to the brain.

• If both assertion and reason are true and reason is the correct explanation of assertion

• If both assertion and reason are true but reason is not the correct explanation of assertion

• If assertion is true but reason is false.

• If both assertion and reason are false