Evolution Of Life On Earth - 1667 Words

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†¦show more content†¦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. Why is fossil evidence in rocks older than 600 million years scarce compared with the number of fossils found in younger rocks? Sedimentary rock forms in layers called strata. Sediment always settles and so the first and oldest stratum is found at the bottom. Newer sediment then settles on top. This means that lower strata are usually older then strata above them. This gives us a way to determine which organism is the oldest. The fossils from the bottom layers of the rock should be the oldest. The earliest organisms had yet to form the ‘hard parts’ that fossils consist of, therefore not being able to be fossilised since most earlier organisms consisted of predominantly soft parts. Organisms of that time and earlier were small, not abundant, and soft bodied. Add in the rock cycle with its weathering, erosion, subduction, melting, and so on, and the reasons are plentiful. There were fewer organisms then since they had only just begun to appear and biodiversity of plants and animals was very little. What type of organism is most likely to be fossilised? -