Q. Life-form on earth originated firstly in which of the following?

[A] Air

[B] Mountain

[C] Water

[D] Soil

Answer: C


  • With an environment devoid of oxygen and high in methane, for much of its history Earth would not have been a welcoming place for animals.
  • The earliest life forms we know of were microscopic organisms (microbes) that left signals of their presence in rocks about 3.7 billion years old. The signals consisted of a type of carbon molecule that is produced by living things.
  • Evidence of microbes was also preserved in the hard structures (“stromatolites”) they made, which date to 3.5 billion years ago. Stromatolites are created as sticky mats of microbes trap and bind sediments into layers. Minerals precipitate inside the layers, creating durable structures even as the microbes die off.

Source: NCERT Class 11