The first major event was when cyanobacteria began photosynthesis during the Proterozoic Epoch. Once cyanobacteria began photosynthesis, they put a lot of oxygen into the atmosphere, helping oxygen persist in the atmosphere because it was usually consumed as soon as it was put out. More oxygen lead to a decrease in some bacteria but multicellular algae, and toward the end of the Proterozoic, the first animals started coming up. This was the most critical event in developing life since without large amounts oxygen in the atmosphere, humans would not survive.
The second main event was the extinction at the end of the Paleozoic Era. The mass extinction got rid of 80% of all the species on earth. It affected marine communities the most by far, causing the extinction of most of the marine invertebrates of the time. Some groups survived the Permian mass extinction in greatly diminished numbers, but they never again reached the ecological dominance they once had, allowing another group to dominate the sea. However, this massive loss of life lead to an explosion of life. The new period that began was the time of the dinosaurs. Life was never the same.
The third main event occurred in the tertiary period. Birds and mammals were began to radiate and flowering plants and insects began to dominate. We know this because the fossils of this time period indicate that. The domination of mammals was the beginning of the evolution of homo sapiens. If mammals began to dominate and grow later or not at all, then humans would probably not be at the stage we are now, or we may not have evolved to be the way we are right now.
The first billion years or so consists of no life on earth. Life shows up quite late on the timeline. The dinosuars existed on the earth for approx 1/3 of all of its history and were the humans of the Mesozoic Era. The only thing that we have evidence of their existence is fossils. Humans show up only in the last 12,000 years. Im amazed that the earth went so long without life and yet we have changed the earth more than it has probably changed in the past 4.6 billion years.
I wonder why only our planet evolved the way it did. How do we know that there were not human-like creatures before us? How much longer can the earth sustain us? What event will mark the beginning of a new era or epoch?
The second main event was the extinction at the end of the Paleozoic Era. The mass extinction got rid of 80% of all the species on earth. It affected marine communities the most by far, causing the extinction of most of the marine invertebrates of the time. Some groups survived the Permian mass extinction in greatly diminished numbers, but they never again reached the ecological dominance they once had, allowing another group to dominate the sea. However, this massive loss of life lead to an explosion of life. The new period that began was the time of the dinosaurs. Life was never the same.
The third main event occurred in the tertiary period. Birds and mammals were began to radiate and flowering plants and insects began to dominate. We know this because the fossils of this time period indicate that. The domination of mammals was the beginning of the evolution of homo sapiens. If mammals began to dominate and grow later or not at all, then humans would probably not be at the stage we are now, or we may not have evolved to be the way we are right now.
We have had a gigantic impact on the earth compared to the amount of time the human race as we know it has existed. All of recorded history does not even make up one second in the clock of the universe. We are already cutting down all the forests, polluting the rivers, and killing off species on a planet that has been around nearly 500 times longer than we have of recorded history. A planet that has taken 4.6 billion years to be made is being destroyed in a few centuries. I think it is far too late to turn back now because these precious things cannot be replaced for a few centuries, and that is long enough for the human race to go extinct.
I wonder why only our planet evolved the way it did. How do we know that there were not human-like creatures before us? How much longer can the earth sustain us? What event will mark the beginning of a new era or epoch?
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