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Biology · 2024 · 5 marks
CBSE 2024 · Region 1 · Set 1 · Q33
(a) (i) Name and explain the property present in normal cells but is lost in cancer cells. (ii) All normal human cells have genes that may become…
(i)
Name and explain the property present in normal cells but is lost in cancer cells.
(ii)
All normal human cells have genes that may become cancerous under certain conditions. Name them and explain how.
(iii)
State the role of the following techniques in detection and diagnosis of cancer :
(1)
Biopsy and Histopathology
(2)
Magnetic Resonance Imaging
Large quantities of sewage are generated every day in cities as well as in towns and are treated in Sewage Treatment Plants (STPs) to make them less polluting. Given below is the flow diagram of stages of STP. Study the flow diagram and answer the questions that follow :
(i)(1)
Why is primary effluent passed into large aeration tanks ?
(2)
What is the 'sediment' formed, referred to as ? Mention its significance.
(3)
Explain the final step in the settling tank before the treated effluent is released into water bodies.
(ii)
Name any two organisms commonly used as biofertilisers, belonging to different kingdoms. Write how each one acts as a biofertiliser.
Marking-scheme solution
(i)
-Contact Inhibition is present in normal cells but not in cancer cells,
-When normal cells come in contact with other cells it inhibits their uncontrolled growth.
(ii)
Cellular oncogenes / Proto-oncogenes , when activated under certain conditions could lead to oncogenic transformation of the cells.
(iii)(1)
Biopsy and histopathology– A piece of suspected tissue cut into thin sections is stained , and examined under microscope by pathologist for increased cell counts.
(2)
MRI – detects cancer of internal organs , uses strong magnetic fields and non–ionising radiations to detect pathological and physiological changes in living tissue
(i)
(1)
In aeration tanks there is growth of aerobic microbes and fungi (flocs) that consume major part of organic matter in effluent thus reducing BOD
• -Activated sludge
• -Used as inoculum in aeration tanks.
(3)
Bacterial flocs are allowed to sediment. ( Activated sludge)
(ii)
-Rhizobium (Bacteria), live symbiotically in nodules of roots of leguminous plants and fix
atmospheric nitrogen into organic form and provide nitrogen to the plant.
-Glomus (fungi), live in symbiotic association with roots of higher plants and absorb phosphorus
from the soil and passes it to plants.
-Cyanobacteria (Anabaena, Nostoc, Oscillatoria),
Add organic matter to the soil and increase fertility (Paddy fields)
All Microbes in Human Welfare questions2024 question paperNCERT solutions: Microbes in Human WelfarePractice Microbes in Human Welfare →
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CBSE Class 12 Biology past-paper question from the 2024 board exam, with the answer as CBSE’s own marking scheme gives it. Where our answers come from.