Subject

Biology

Class

CBSE Class 12

Pre Boards

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Sample Papers

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 Multiple Choice QuestionsLong Answer Type

31.

(a) Write the specific location and the functions of the following cells in human males:

(i) Leydig cells

(ii) Sertoli cells

(iii) Primary spermatocyte

(b) Explain the role of any two accessory glands in human male reproductive system.

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32. Explain the salient features of Hugo de Vries theory of mutation. How is Darwin theory of natural selection different from it? Explain.


Hugo de Vries based on his work on evening primrose suggested that variations occurred due to mutations. Hugo de Vries gave the name saltation (single step large mutation) to the mutations that brought about speciation. Darwin aboard the H.M.S Beagle observed that all existing living forms share similarities among themselves and also with other life forms that existed millions of years ago of which many are extinct. The evolution of life forms has been gradual and those life forms better fit in environments that leave more progeny. This is called natural selection and is a mechanism of evolution. Mutations are random and directionless while the variations that Darwin talked about were small and directional.
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33.

(a) Name the primates that lived about 15 million years ago. List their characteristic features.

(b) (i) Where was the first man-like animal found?

(ii) Write the order in which Neanderthals, Homo habilis and Homo erectusappeared on earth.

State the brain capacity of each one of them.

(iii) When did modern Homo sapiens appear on this planet?

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34.

(a) Explain primary productivity and the factors that influence it.

(b) Describe how do oxygen and chemical composition of detritus control decomposition?

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35.

(a) What is El Nino effect? Explain how it accounts for biodiversity loss.

(b) Explain any three measures that you as an individual would take, to reduce environmental pollution.

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