Final answer:
The building blocks of life formed cells through abiogenesis, where carbon-based molecules became surrounded by lipid molecules and evolved the ability to reproduce. Another hypothesis suggests that life may have arrived on Earth from space on asteroids or meteorites. However, in the present time, cells can only come from pre-existing cells.
Step-by-step explanation:
The building blocks of life ultimately formed cells through a process called abiogenesis. Most scientists believe that early Earth had the necessary conditions for the formation of cells, such as warm seas with carbon-based molecules and energy input from lightning and volcanoes. Around 3.5 billion years ago, carbon-based molecules became surrounded by lipid molecules, which led to the evolution of the first cells. Another hypothesis suggests that life may have arrived on Earth from space on asteroids or meteorites. However, in the present time, cells can only come from pre-existing cells.