Evolution – important questions for Boards 2027

CBSE Class 12 Biology

1. VSA · 0.5 marks

   What is the proposal that life or life-spores reached Earth from outer space called?

   Answer

   Panspermia is the proposal that life-spores were transferred to Earth from outer space.

2. VSA · 1 mark

   Name the naturalist who reached conclusions about natural selection similar to Darwin’s around the same time.

   Answer

   Alfred Wallace, a naturalist working in the Malay Archipelago, reached conclusions similar to Darwin’s around the same time.

3. SA · 1.5 marks

   Approximately when did life appear on Earth, and how long after Earth formed was this? (1.5)

   Answer

   Earth was supposed to have been formed about 4.5 billion years back. Life appeared 500 million years after Earth formed, i.e., almost four billion years back. There was no atmosphere on early earth.

4. SA · 2 marks

   Explain how natural selection acts on heritable variations that improve survival and reproductive fitness in an environment. (2)

   Answer

   A population has built-in heritable variation. Individuals whose characteristics enable better survival under natural conditions have greater reproductive fitness, leave more progeny, and are selected by nature, driving evolution.

5. MA · 3 marks

   Describe the Big Bang theory and state how the expansion and cooling of the universe led to the formation of hydrogen, helium and galaxies. (3)

   Answer

   1. The Big Bang theory explains the origin of the universe as a singular huge explosion, unimaginable in physical terms. The universe expanded, and its temperature came down; hydrogen and helium formed sometime later. 2. Gases condensed under gravitation and formed the galaxies of the present-day universe. Galaxies contain stars and clouds of gas and dust.

6. LA · 5 marks

   Explain how analogous structures differ from homologous structures and identify the type of evolution associated with analogy. Give two examples of analogous structures and explain how similarities in proteins and genes can provide evidence of common ancestry.

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7. MCQ · 1 mark

   Which statement correctly describes the conclusion of Karl Ernst von Baer’s study of vertebrate embryos? (A) Embryos pass through the adult stages of other animals. (B) Embryos never pass through the adult stages of other animals. (C) Embryos have no features in common. (D) Embryos prove that all vertebrates are identical.

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8. SA · 2 marks

   How do fossils preserved in different sedimentary layers provide evidence for evolution? (2)

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9. MA · 3 marks

   What did the theory of spontaneous generation propose? Briefly state how Pasteur’s experiments refuted it. (3)

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10. MCQ · 1 mark

    Mammalian forelimbs with the same basic bones but different functions are an example of: (A) analogous structures (B) homologous structures (C) vestigial structures (D) acquired characters

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