Earth, the planet in which we live is about 4.5 billion years old. Due to the presence of water, Earth is also known as watery planet or blue planet. Out of all planets, Earth is the only planet that contains both oxygen and water and therefore supports life. But, why it is the only planet? Is does earth made of some specific type of matter? Do some special types of processes were involved in the formation of Earth? Certainly no. Then, why other planets neglect life and are not considered as the Earth. The answer can be predicted by knowing the evolution of life on Earth. If we know how life started and which things actually happen at that time, we can find why Earth is the only planet where life is possible. Keep on reading this article for knowing about the evolution of life on Earth.
How Earth Formed?
Although there is a no fact that can tell us how exactly life originated, what exactly happened and why it happened? But, through the help of fossil records, many questions related to life’s beginnings have been answered by scientists and researchers. It is because of oldest fossils called zircon crystals that many predications about life’s existence have been made by researchers. Two gases called helium and hydrogen led to the formation of Earth about 4.6 billion years ago. The sun was formed from gases and dust particles and then continued to shrink because of some gravitational forces. Then, these gravitational forces of sun lead to a process called nuclear fusion. This process give out heat, light and other radiations. As the process happened, the gas and dust particles that surrounded the sun form into small chunks called planetesimals or modern day planets. Then, the Earth was passed through three particular stages – Hadean, Archean, and Proterozoic. During these stages, many gases such as methane, ammonia, nitrogen, hydrochloric acid, etc. was formed through various volcanic eruptions that occur besieged the Earth. The earlier structure that was surrounded by dust and debris was changed into a solid sphere that was pulled towards an orbit of the sun.
- About 3.8 billion years ago, a prokaryotic cell called bacteria was formed
- Then after 570 million years, molecular life was evolved with arthropods, fishes, plants and animals
- Then, after 200, 00 years, the Homo sapiens species was also founded by scientists.
Some Theories on the Origin of Life
- Panspermia – According to this theory, life was brought to earth from any other place in the space. It states that some meteorites or microbes (micro-organisms) reach to earth through some activities created by rocks and other material.
- Electric Spark – Researchers assume that light may have provided the spark which is required for the beginning of life. According to Miller-Urey experiment, electric sparks lead to the generation of amino acids, sugars, methane, water, hydrogen and other things present in the atmosphere are required for surviving on Earth
- Cold Start – It was happened that ice might have covered the 5 oceans of the world 2 billion years ago. This ice might have prevented organic compounds (present in the water) from UV rays and harm from cosmic impacts. These compounds may have lead to the origin of life.
- Role Of Clay – According to Alexander Graham Cairns, an organic chemist, clay are the first molecules of life. And these molecules might have concentrated several organic compounds together and help them to grow like genes. Working in this fashion, these compounds might evolve into necessary things required for surviving on Earth.
- Simple Start – It is not just the RNA or DNA molecules have led to the origin of life. But, life could also be started from smaller, simple molecules that interact with one another and undergo many reactions. Other complex molecules such as RNA might have helped the smaller molecules and enhanced metabolism to form life.
The blue planet, Earth is not new. It has been with us since 4.6 billion years. The fusion process that occurred in sun led to the formation of all eight planets. The heat, radiations, helium and oxygen helped in continuing the life for longer periods. Some scientists believe that life originated from ice glaciers. While other scientists believed that simple and small organisms led to the evolution of life. But, there is no theory that clearly answers questions related to life’s beginning on the Earth.
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