Life is the power that organisms possess to maintain their existence and reproduce themselves. Various scientists proposed different theories regarding the origin of life. Some popular theories are discussed below;
According to this theory, all plants and animals existing on the earth today are created by the supernatural power of a god.
Ancient Chinese, Greek and Egyptian believed in spontaneous generation of life. According to this, "Life is originated from nonliving things or abiotic factors gradually or automatically." Eg; frog, fish, snail were formed by clay.
According to this theory, "the new organism is originated from pre-existing ones."
Francesco Redi(1684) demonstrated to show maggots could not be formed from the flesh of meat, but the smell of meat attracted the flies which lay eggs. When eggs hatch, maggots appeared on meat. For that, he has taken 8 jars in which he kept a piece of boiled meat in all of them. 4 jars are made sealed whereas remainings are opened. He found the maggots in opened jars rather than sealed jars.
Lazzaro and spanllanzenil(1969)
They performed an experiment to conclude unicellular organism could not originate from nonliving things. For that 8 bottles are taken with heg influsion. 4 of them are corked and remaining are made air-tight. After few days, they found microorganisms in corked bottles not in air-tight bottles.
Louis parleus(1862) disproved the concept given by abiogenesis and performed the experiment with swan neck flask supporting biogenesis.
Ritcher(1864) believed that life on earth originated from spores came from other planets called panspermia.