Miller and Urey were two scientists who were researching the Earth's early atmosphere. There experiment imitated the inorganic conditions though to be present during the origin of life and tested the chemical origin of life under those conditions in a closed circulating system. Through there experiment they were able to create and pull out 25 amino acids that are necessary to human life and could be made under the conditions believed to be on earth at the time. This created a huge boom in the scientific community as it was believed that this could be the explanation to the origin of life.
RNA
It is hypothesized that the evolution of RNA came before the evolution of DNA. This is because every living creature on Earth has RNA which acts as an aid in hereditary processes whether it be asexual or sexual. In addition, many chemical reactions needed for life, including transcription, are catalyzed by RNA.
Adaptive Radiation
Adaptive radiation is the idea that organisms diversify rapidly into a multitude of new forms after a random event destroys a large number of old predators. The remaining organisms are then able to thrive in niches that they wouldn't have been able to access before. Because these organisms would have been in new environments, their populations would have evolved to fit the new niches.This is often used to explain how all living organisms can have a common ancestor yet so many forms of life.
Homeobox Genes
Homeobox genes are large families of similar genes that direct the formation of many body structures during the early stages of embryonic development. Through evolution, these genes were eventually "turned off" and failed to tell the embryo to develop a certain portion of the body. However, today these genes can sometimes still be turned back on. For example, it is possible for a snake to be born with legs or for a chick to be born with teeth because these ancient genes got turned back on.