Life on Earth Essay

Life on Earth Students Name: School Name: Life on earth How life originated on earth is a question that people have pondered for ages. Scientists have tried to answer this question through many theories and experiments. One of the first hypotheses to explain the origin of life on earth was proposed by Aristotle (383-322 B.C.) and it was widely accepted until the seventeenth century. He proposed spontaneous generation, the concept that living things arise from nonliving things. As time passed, people began to question this long-held belief and proposed an alternative idea, called biogenenis. This is the concept that life originated only from preexisting life. An experiment was carried out by a scientist named Redi and he challenged spontaneous generation where he demonstrated that maggots did not come from decaying meat, but from eggs of flies. Several hypotheses have been carried out to prove if it is true that living things come from living things. Today there are three competing theories of the origin of life on Earth that is; the extraterrestrial source, heterotroph origin and autotroph origin. Extraterrestrial life is defined as life that does not originate from earth. Consequently there are hypotheses that have supported this theory which are as follows :Panspermia is an hypothesis that suggests that the seeds of life are prevalent throughout the Universe and life on Earth began by such seeds landing on Earth and propagating .in other words life arose outside the earth and that living things were transported to earth in addition there are evidences that support this hypothesis they are as follows, evidence drawn from meteorites which suggests that the meteorites from mars to earth were found to contain complex organic molecules and may have supported life; another evidence is drawn from mars exploration which states that bodies of water which previously existed may have supported life on earth. An additional hypothesis involves chemical evolutions which pro...