Evolution Of Life On Earth

1667 WordsMay 5, 20167 Pages
Fossils can provide us with a great deal of information about the past. They can also help us to understand the present. When do we believe life on earth originated? The earth cooled from its formation 4.6 billion years ago. Life on earth began 3.5 billion years ago, evidence supporting this statement is that the earliest fossils were found from up to 3.5 billion years ago. The following steps are believed to be the major stages in the evolution of life on Earth: 1. The formation of organic molecules Complex organic molecules formed in water on the early Earth. 2. The formation of membranes A membrane developed to isolate and protect the system of large complex organic molecules which evolved to include nucleic acids and became capable of self-replication. 3. Procaryotic Cells The first cells were simple structures known as procaryotes. They are the earliest type of fossil found. 4. Eucaryotic Cells Cells containing a membrane-bound nucleus and cell organelles developed. 5. Colonial cells Multicellular organisms may have originated when daughter cells became bound together after cell division to form an aggregation of similar cells or colony. Stromatolites provide an example of this both as fossils and as present-day colonial cells. 6. Multicellular organisms Multicellular organisms containing cells which show specialisation of function evolved. Each cell has its own particular function and is dependent on others. Each organism, however, functions as co-ordinated
Open Document