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Biology · 2025 · 2 marks
CBSE 2025 · Region 7 · Set 3 · Q20
(a) Ravi lives in a village where he suggested to the local farmers to introduce a fungus as biofertilizer into their crop fields. State the benefits…
(a)
Ravi lives in a village where he suggested to the local farmers to introduce a fungus as biofertilizer into their crop fields. State the benefits provided by the fungus to the crop.
OR
(b)(i)
How do secondary lymphoid organs provide immunity?
(ii)
Highlight the role of spleen as an organ that provides immunity.
Marking-scheme solution
(a)
-Absorbs phosphorus from soil and passes it to the plant.
-Plants became resistant to root-borne pathogens.
-Plants become tolerant to salinity and drought.
-Overall increase in plant growth and development.
OR
(b)(i)
Secondary lymphoid organs provide sites for interaction of lymphocytes
with antigens , which then proliferate to become effector cells.
(ii)
Spleen :
Has lymphocytes and phagocytes , Filters blood by trapping blood borne microorganisms.
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CBSE Class 12 Biology past-paper question from the 2025 board exam, with the answer as CBSE’s own marking scheme gives it. Where our answers come from.