The life on earth has evolved though many stages. The history traces back to many years and they explain the process by which the organisms had evolved from day one until today. Our planet came into existence about 4.5 billion years ago. For many years, ours was a lifeless planet and there were no traces of life anywhere. But one billion years from now, life started to come into existence and started multiplying. Full report on History of Life on Earth is explained here.
It is observed that there are certain similarities between all the species on earth today. Many common factors are found. But there are some peculiar characteristics which differentiated all the species. Even under a single species group, each living being is different. Although we can find many new species, almost 99% of the species are extinct. Some of them survived for few years but they were not able to adjust to the surroundings and hence did not exist anymore. At the very first, oxygenic photosynthesis process took places. This led to the addition of oxygen in the atmosphere. It was the prime reason for evolution of life on the earth. After that cells with organelles came into existence.
Talking about the earliest land plants, they came into picture about 450 million years ago. While talking about the oldest fragments, we can say traces of life were seen 4.55 billion years ago. The earliest living beings found here were very minute in size and contained very less or no features. They were simple shaped living beings. When these living beings died, their remains were similar to that of a rod shaped substance. This proof was not sufficient to tell the details of this living being because they were formed through abiotic physical processes. Some scientists are of the view that the oldest living creatures to grow on Earth were the fossilized bacteria. This was proven with some geochemical process. The problem here was that these beings were put on a close research, and it was found that they were produced as a result of some non- biological process. Hence we cannot term them as pure living beings. These structures were of some chemical origin, hence we cannot mark is as a pure evidence of life on Earth.
Biologists have a theory that any of the living being which is into existence should have some ancestor to bring the generation. Without this fact, you cannot prove that this is a creature formed by biological process. The reason is that it is not possible that separate lineages could develop independently. There has to be some strong biological or ancestral connection. If we look at the variety of species we have now, we can broadly divide the source of beings as the ones who came in into life spontaneously and the ones who seeded from somewhere else. Greek philosopher Anaximander was the first person to propose the theory of “life seeding from somewhere else”. There are two parts in this theory. The first case is when fragments throw themselves into the space by some meteor effect. The main source in this theory can be the planets of Mars and Venus. Second case is when aliens visit the planet Earth, they bought with them some microorganisms which stayed back here and multiplied as they got favorable climate here to thrive well. There is one more possibility that microorganisms might have come from the outer space by some natural means. Many of the tests made on them revealed many facts about them. One fact was that they can survive all the shocks and exposure of being thrown into space and then brought to Earth.
Other theory was that the earliest organisms didn’t have any base. They occurred and came into existence on their own without any external force. Life here is sustained by carbon and water. Carbon Dioxide is exhaled out by most of the organisms and carbon helps in some of the complex chemical processes. Water also plays a major part in helping the organisms survive. It serves as an excellent solvent. In the winter season the water is transformed into ice and forms a layer in rivers and lakes. This layer of ice helps the living beings beneath it to survive and be protected by the cold weather outside. The chemical composition of water is such that you get to make many other solvents from it and its acts as a good base to help control unwanted chemical reactions. Ammonia also is a good solvent as it helps the living organisms to balance their chemical reactions and control and sustain life. Talking about increase in the number of organisms since the day they first came into existence, the process of replication was very important. Self-replication is the process where the organism produces its own kind.
Research and studies have come up with other theories too. The simplest member of the living group consists of DNA in their bodies which say a lot about their origin and future. This DNA helps in maintaining the self-replication process. When it comes to the origin of life, many varied theories came up. One theory says that RNA molecules can catalyze by themselves. Later on DNA was replaced by RNA as RNA molecules are more stable and they can build more organisms due to their capability. They were also called as “protein factories”. To go deep into this study, scientists have artificially produced RNA in laboratories. There was another theory which said that double-walled bubbles of lipids were the first step in the process of formation of living organelles. Based on the research done, they have enough proof to support the fact that the conditions of early earth were due to the formation of lipids. These got transformed into liposomes and got multiplied many times in a short duration. In 2003, a report was made which stated that fatty acids were converted into bubbles and these bubbles were encapsulated into RNA which gave birth to life forms.
It is believed that plants are differentiated from animals by one fact. Animals are multi cellular beings and they lack a layer of cell walls which is present in fungi and algae. The bodies of animals are differentiated into various tissues. They have a separate layer of muscles which help in the movement of body parts by alternate contraction and relaxation, while the nerves are important since they are responsible for transmitting signals across the body.
Thus, any change in the evolution of mankind is observed closely. Evolution is nothing but any change in the successive generations with respect to some characteristics and biological populations. This is because of life of earth and evolution since then, we are able to see the diverse cultures and people around. Individuals are all similar. The only difference is they are made up of DNA and protein molecules and each of the species has different formation and composition of DNA as well as molecules. Some of them are almost similar while some others possess altogether different qualities. Thus almost 99 percent of the species come to form over five billion species on earth. Almost 1.2 million have been traced and documented well. The remaining 86 percent have no proof about them as they are not in any written form.
Life on Earth and its history is a subject that has baffled many scientists and researches all across. Here are a few theories that explain the History of Life on Earth.