GEOLOGY

Detailed explanation-1: -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.

Detailed explanation-2: -The first ever living organism on Earth was a bacteria known as cyanobacteria.

Detailed explanation-3: -In the oceans of our young planet, bacteria were among the first forms of life to emerge. Long before plants or animals had evolved, bacterial colonies flourished and grew.

Detailed explanation-4: -They were the only life forms until about 2.1 billion years ago. Other life forms evolved from bacteria. Bacteria grow, reproduce, and carry out respiration.

Detailed explanation-5: -It has been proposed that archaea evolved from gram-positive bacteria as a response to antibiotic selection pressures. Microbial mats and stromatolites represent some of the earliest prokaryotic formations that have been found.