Subject

Biology

Class

CBSE Class 12

Pre Boards

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Sample Papers

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 Multiple Choice QuestionsShort Answer Type

1.

Why is the enzyme cellulase needed for isolating genetic material from plant cells and not from the animal cells?


Cellulase is the enzyme that digests cell wall. Since plant cells have cell wall, so to digest the cell wall, cellulase is required. Animals do not have cell wall so, no cellulase required.

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2.

An anther with malfunctioning tapetum often fails to produce viable male gametophytes. Give any one reason.


Tapetum nourishes the developing pollen grain so in case of a  malfunctioning tapetum the pollen grain will not get any nourishment and lose its viability.

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3.

Why sharing of injection a needle between two individuals is not recommended?


Sharing of injection needles between two individuals is not recommended because it may lead to the transmission of HIV-infection and cause AIDS.

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4.

Name the enzyme and state its property that is responsible for continuous and discontinuous replication of the two strands of a DNA molecule.


The enzyme involved in the process of replication is DNA dependent DNA polymerase. This enzyme catalyzes polymerization only in one direction, i.e., 5’ → 3’. As a result on template strand with 3’ → 5’ the replication is continuous while on the template strand with polarity 5’→3’ replication is discontinuous.

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5.

Write the equation that helps in deriving the net primary productivity of an ecosystem.


GPP – R = NPP (where GPP = Gross Primary Productivity, R = Respiratory losses and NPP = Net Primary Productivity)

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6.

Name the type of biodiversity represented by the following:

(a) 50,000 different strains of rice in India.

(b) Estuaries and alpine meadows in India.


The type of diversity represented by the following is:

(a) 50,000 different strains of rice in India represent genetic diversity

(b) Estuaries and alpine meadows in India represent ecological diversity
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7.

Geitonogamous flowering plants are genetically autogamous but functionally cross-pollinated. Justify.


In geitonogamy the pollen grains are transferred from the anther to the stigma of another flower on the same plant, thus functionally it involves cross-pollination. Since the pollen grains come from the plant it is genetically similar to autogamy.

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8.

When and where do chorionic villi appear in humans? State their function.


Chorionic villi appear on the trophoblast after implantation. Chorionic villi interdigitate with the uterine tissues and jointly forms the placenta which is a structural and functional unit between developing embryo and maternal body.

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9.

Identify the examples of convergent evolution from the following:

(i) Flippers of penguins and dolphins

(ii) Eyes of octopus and mammals

(iii) Vertebrate brains

The examples of convergent evolution are:

(i) Flippers of penguins and dolphins

(iii) Eyes of octopus and mammals

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10.

Write the importance of MOET.


MOET – Multiple Ovulation Embryo Transfer is a method in which a cow is administered hormones with FSH (follicular stimulating hormone) like activity. These hormones induce follicular maturation and superovulation in which the cow produces 6–8 eggs per cycle instead of one egg. The cow is mated with an elite bull or artificially inseminated and the fertilized eggs at 8-32 stage is recovered non-surgically and transferred to a surrogate mother.

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