Origin of Life

The sun and its planets formed between 5 and 4.6 billion years ago as matter in our solar system began to coalesce because of gravity. By about 3.9 billion years ago, the Earth had an atmosphere that contained the right mix of hydrogen, oxygen, carbon and nitrogen to allow for the creation of life. Scientists believe that the energy from heat, lightning, or radioactive elements caused the formation of complex proteins and nucleic acids into standards of replicating genetic code. These molecules then organised and evolved to form the first simple forms of life. 3.8 billion years ago, conditions became right for the fossilisation of the Earth’s early cellular life forms. These fossilised cells resemble present – day cyanobacteria. Such cells are known as prokaryotes . Prokaryote cells are very simple, containing few specialised cellular structures and their DNA is not surrounded by a membranous envelope. The more cells of animals and plants, known as eukaryotes, first showed up about 2.1 billion years ago. Eukaryotes have a membrane – bound nucleus and many specialised structures located within their cell boundary. By 680 million years ago, eukaryotic cells were beginning to organise themselves into multicellular organisms. Starting at about 570 million years ago an enormous diversification of multicellular life occurred known as the Cambrian explosion. During this period all but one modern phylum of animal life made its first appearance on the Earth.


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