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Science · 2022 · 2 marks
CBSE 2022 · Region 1 · Set 1 · Q7
What is ozone ? How is it formed in the upper layers of the Earth's atmosphere ? How does ozone affect our ecosystem ?(b)List two human-made ecosystems.(ii)"We do not clean a pond in the same manner as we do in an aquarium." Give reason to justify this statement.
What is ozone ? How is it formed in the upper layers of the Earth's atmosphere ? How does ozone affect our ecosystem ?
(b)
List two human-made ecosystems.
(ii)
"We do not clean a pond in the same manner as we do in an aquarium." Give reason to justify this statement.
Marking-scheme solution
Ozone is a molecule formed by three atoms of oxygen.
UV radiations split some molecular oxygen \(\displaystyle \left(\mathrm{O}_{2}\right)\) into free oxygen atoms \(\displaystyle (\mathrm{O}+\mathrm{O})\). These atoms then combine with molecular oxygen to form ozone. /
\[\begin{aligned}
& \mathrm{O}_{2} \xrightarrow{\mathrm{UV}} \mathrm{O}+\mathrm{O} \\
& \mathrm{O}+\mathrm{O}_{2} \rightarrow \mathrm{O}_{3}(\mathrm{Ozone})
\end{aligned}
\]
Ozone layer shields the surface of the earth from damaging UV radiation of the sun. / Depletion of ozone layer causes harmful effects on the organism.
i) Aquarium, crop field, gardens, etc.
(ii)
A pond is a natural ecosystem. It has decomposers whereas an aquarium is an artificial ecosystem and does not contain decomposers. Therefore it needs regular cleaning for proper functioning.
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CBSE Class 10 Science past-paper question from the 2022board exam, with the answer as CBSE’s own marking scheme gives it. Where our answers come from.