Subject

Biology

Class

CBSE Class 12

Pre Boards

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Sample Papers

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 Multiple Choice QuestionsShort Answer Type

1.

State Gause's Competitive Exclusion Principle.


Gause's Competitive Exclusion Principle states that two closely related species competing for the same resources cannot co-exist indefinitely and the competitively inferior one will be eliminated eventually. This may be true if resources are limiting, but not otherwise.

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2.

Mention any two contrasting traits with respect to seeds in pea plant that were studied by Mendel.


The two contrasting traits with respect to seeds in pea plant that were studied by Mendel are:
Seed shape - Round seeds and Wrinkled seeds.
Seed colour- Yellow and Green.

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3.

Why is secondary immune response more intense than the primary immune response in human?


Secondary immune response is more intense than the primary immune response because our body appears to have memory of the first encounter that recognize the pathogen quickly on subsequent exposure and overwhelm the invaders with a massive production of antibodies.

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4.

Why is it not possible for an alien DNA to become part of a chromosome anywhere along its length and replicate normally?


The replication does not initiate randomly at any place in DNA it only starts at the site of origin of replication (ORI), thus it is not possible for an alien DNA to become part of a chromosome  anywhere along its length and replicate normally .

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5.

Name the part of the flower which the tassels of the corn-cob represent.


Tassels of the corn represent stigma and the style of the flower.

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6.

In Snapdragon, A cross between true breeding red flower (RR) plants and true breeding white flower (rr) plants showed a Progeny of plants with all pink flowers.

(a)The appearance of pink flowers is not known as blending. Why?(b)What is the phenomenon known as?


(a) The appearance of pink color is not caused as blending because the alleles do not mix or blend and they maintain their originality and reappear in F2 generation. The pink color appears just because the Dominant allele is not completely dominant over the recessive allele for colour.

(b) The phenomenon is called incomplete dominance.

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7.

Name the enzymes that are used for the isolation of DNA from bacterial and fungal cells for recombinant DNA technology.


The enzymes that are used for the isolation of DNA from bacterial and fungal cells for recombinant DNA technology are:

Lysozyme is used to isolate DNA from bacteria.

Chitinase is used to isolate DNA from fungus.

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8.

Name the type of association that the genus Glomus exhibits with higher plants.


Glomus forms Mycorrhizae with the higher plants and exhibits Mutualism.

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9.

Why are the human testes located outside the abdominal cavity? Name the pouch in which they are present.


Human testes are located outside the abdominal cavity for maintaining low temperature (2–2.5o C lower than the normal internal body temperature) necessary for spermatogenesis.

The pouch in which they are present. is called Scrotal sacs.

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10.

State the role of C-peptide in human insulin.


C-peptide is the extra stretch of polypeptide which makes the insulin inactive (proinsulin).

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