Evolution Of Life On Earth

Evolution is a change in the characteristics of living things over time. As per Darwin, evolution occurs by a process called natural selection. In natural selection, some members of a species, being better adapted or suited to their environment, produce more offspring than others, so they pass advantageous traits to their offspring. Over many generations, this can lead to major changes in the characteristics of the species. Evolution explains how living things are changing today and how modern living things have descended from ancient life forms that are no longer part of the earth’s life. As living things evolve, they generally become better suited for their environment. This is because they evolve adaptations. 

The Origin of The Earth

The Big Bang Theory is a theory that explains the origin of the universe. As per the theory, a singular huge explosion took place, unimaginable in physical terms. The universe expanded, and hence, the temperature came down. Hydrogen and Helium formed sometime later. The gasses condensed under gravitation and formed the galaxies of the present-day universe. In the solar system of the milky way galaxy, the origin of the earth took place about 4.5 billion years back. There was no atmosphere on earth initially. Water vapour, methane, carbon dioxide and ammonia released from molten mass covered the surface. The UV rays from the sun broke up water into hydrogen and oxygen, and the lighter hydrogen escaped. Oxygen is combined with ammonia and methane to form water, CO2 and others. The ozone layer was formed. As it cooled, the water vapour fell as rain to fill all the depressions and form oceans. Life origin took place on earth about 500 million years after the formation of the earth, i.e., almost four billion years ago.

Theory of Evolution of Life on Earth

Based on observations made during a sea voyage in a sailing ship called HMS. Beagle around the world, Charles Darwin observed that existing living forms share similarities to varying degrees not only among themselves but also with earth life forms that existed millions of years ago. Many such earth life forms are extinct now. There had been extinctions of different life forms in the years gone by, just as new life origins happened at different periods of the history of the earth. There has been a gradual evolution of life. Any population has a built-in variation in characteristics. Those characteristics which enable some to survive better in natural conditions, i.e. climate, food, physical factors, etc., would outnumber others that are less capable of surviving under such natural conditions. This is called the survival of the fittest. Fitness, according to Darwin, refers ultimately and only to reproductive fitness. Hence, those who are a better fit in an environment leave more offspring than others. These are, hence, selected by nature. He called it natural selection and demonstrated it as a mechanism of evolution. Alfred Wallace, a naturalist who worked in the Malay Archipelago, had also come to similar conclusions around the same time. All the existing earth life forms share similarities and share common ancestors. However, these ancestors were present at different periods in the history of the earth (epochs, periods and eras). The geological history of the earth closely correlates with the biological history of the earth.

Evolution Evidence

Different-aged rock sediments contain fossils of different life forms who probably died during the formation of the particular sediment. Some of them appear similar to modern organisms. They represent extinct organisms, e.g. dinosaurs. A study of fossils in different sedimentary layers indicates the geological period in which they existed. The study showed that life forms varied over time, and certain life forms are restricted to certain geological timespans. Hence, new forms of life have arisen at different times in the history of the earth. All this is called paleontological evidence. Comparative anatomy and morphology show similarities and differences between earth life of today and those that existed years ago. Such similarities can be studied to understand whether common ancestors were shared or not among organisms. For example, whales, bats, cheetahs and humans share similarities in the pattern of bones and forelimbs. Though these forelimbs perform different functions in these animals, they have similar anatomical structures. Hence, in these animals, the same structure developed in different directions due to adaptations to different needs. This is divergent evolution, and these structures are homologous. Homology indicates common ancestry.

Conclusion:

Evolution is a change in the characteristics of living things over time. The Big Bang theory explains the origin of the universe and of the earth. Charles Darwin observed that existing living forms share similarities to varying degrees not only among themselves but also with earth life forms that existed millions of years ago. As per Darwin’s theory, those who are a better fit in an environment leave more offspring than others. These are, hence, selected by nature. He called it natural selection and demonstrated it as a mechanism of evolution. Comparative anatomy and morphology show similarities and differences between the life of today and those that existed years ago. Such similarities can be studied to understand whether common ancestors were shared or not among organisms.