Читать книгу Oceans For Dummies - Joseph Kraynak - Страница 46

So how did life begin? Well, honestly we still don’t know for sure. One theory is abiogenesis — that life spontaneously arose from non-living material. Another theory, called panspermia, suggests that life came from space on a comet or asteroid. But the leading theory is the RNA World Hypothesis. RNA is similar to DNA but is structured as a single strand as opposed to a double strand and is made up of different nucleobases (the molecular building blocks of RNA and DNA). According to the RNA World Hypothesis, early life on Earth originated with simple RNA molecules that were able to self-replicate (create copies of themselves) and create protein molecules — organic compounds that are an essential part of all living organisms.

Another quality of RNA that makes many scientists believe that RNA drove early evolution is that it has the capacity to evolve through interactions with its environment. The RNA World theory has it that diverse RNA molecules formed (how this happened is still not known) and began to evolve and compete for survival. As they evolved, some RNA molecules began to cooperate with one another to develop genetic code, form proteins, and build cells. Eventually, RNA gave rise to DNA, which has the capacity to store more complex blueprints for living things.