(a) Select the homologous structures from the combinations given

Subject

Biology

Class

CBSE Class 12

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 Multiple Choice QuestionsShort Answer Type

1.

How many chromosomes do drones of honeybee possess? Name the type of cell division involved in the production of sperms by them.

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2.

What is a cistron?

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3. Retroviruses have no DNA. However, the DNA of the infected host cell does possess viral DNA. How is it possible?
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4. Why do children cured by enzyme-replacement therapy for adenosine deaminase deficiency need periodic treatment?
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5. List two advantages of the use of unleaded petrol in automobiles as fuel.
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6.

Why do moss plants produce very large number of male gametes? Provide one reason. What are these gametes called?

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7.

(a) Select the homologous structures from the combinations given below :
(i) Forelimbs of whales and bats
(ii) Tuber of potato and sweet potato
(iii) Eyes of octopus and mammals
(iv) Thorns of Bougainvillea and tendrils of Cucurbita

(b) State the kind of evolution they represent.


 (a) Homologous organs or structures are those that are similar in anatomy or structure and have a common origin, but perform different functions.
From the given options, following are homologous structures:

i. Forelimbs of whales and bats are similar in structure but perform different functions of swimming and flying, respectively.

ii. Thorns of Bougainvillea and tendrils of Cucurbita are both modifications of a stem arising from axillary bud but perform different functions of protection (thorns) and climbing (tendrils), respectively.

(b) The evolution represented by homologous organs or structures is divergent evolution as they have a common origin but have diverged (became dissimilar) with time into different structures performing different functions.

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8.

(a) Why are the plants raised through micro-propagation termed as somaclones?
(b) Mention two advantages of this technique.

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9.

Explain the different steps involved during primary treatment phase of sewage.

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10. What is mutualism? Mention any two examples where the organisms involved are commercially exploited in agriculture.
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