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CBSE Class 12 Biology Solved Question Paper 2018

Short Answer Type

How do cytokine barriers provide innate immunity in humans?

Write the dual purpose served by Deoxyribonucleoside triphosphates in the polymerisation.

Write the names of the following :
(a) A 15 mya primate that was ape-like
(b) A 2 mya primate that lives in East African grasslands

Mention the chemical change that proinsulin undergoes, to be able to act as mature insulin.

Name two diseases whose spread can be controlled by the eradication of Aedes mosquitoes.

6.
How did a citizen group called Friends of Arcata Marsh, Arcata, California, USA, help to improve water quality of the marshland using Integrated Waste Water Treatment ? Explain in four steps.

Wastewater including sewage can be treated in an integrated manner, by utilising a mix of natural and artificial processes.

The conventional sedimentation, filtering and chlorine treatments are given. After this stage, lots of dangerous pollutants like dissolved heavy metals still remain.
To combat this, an innovative approach was taken and the biologists developed a series of six connected marshes over 60 hectares of marshland.
Appropriate plants, algae, fungi and bacteria were seeded into this area, which neutralises, absorb and assimilate the pollutants. Hence, as the water flows through the marshes, it gets purified naturally.
The marshes also constitute a sanctury, with a high level of biodiversity in the form of fishes, animals and birds.

Your advice is sought to improve the nitrogen content of the soil to use for cultivation of a non-leguminous terrestrial crop.

(a) Recommend two microbes that can enrich the soil with nitrogen.

(b) Why do leguminous crops not require such enrichment of the soil?

You have obtained a high yielding variety of tomato. Name and explain the procedure that ensures retention of the desired characteristics repeatedly in large populations of future generations of the tomato crop.