Final answer:
The early atmosphere of Earth contained ammonia, methane, water vapor, and carbon dioxide, but little oxygen. These gases were formed through volcanic activity and lightning-induced chemical reactions. Complex chemical reactions in the absence of oxygen led to the production of amino acids, proteins, and other building blocks of life.
Step-by-step explanation:
The early atmosphere of Earth contained substances like ammonia, methane, water vapor, and carbon dioxide, but only a trace of oxygen. These gases were present due to volcanic activity and chemical reactions sparked by lightning. The absence of oxygen allowed complex chemical reactions to occur, leading to the production of amino acids, proteins, and other chemical building blocks of life. The combination of these building blocks ultimately gave rise to living organisms.