This is the third part of The Ancients, a series of posts describing Earth’s history and the creation of life; all with informal talk and funny quips from yours truly. You should check out the first and second parts before this one.
Name: Proterozoic
Era: 2500-541 m.y.a
Average Temperature: 5-45 Celsius
Atmospheric oxygen: 0-12%
The Proterozoic-a time just before the evolution of complex life. That means that the building blocks of life formed in this eon. That means lower temperatures (Yup! It took this long for the temperature to go down after the VOLCANO ERUPTIONS.), and OXYGEN. We will talk about that later. First, the Snowball Earth hypothesis. It sounds lame but bear with me. Basically, many scientists believe that about 650 million years ago, there was this Cryogenian period, where snow and ice covered the Earth almost entirely, SEVERAL TIMES. It was basically the Ice Age, but better and less well known.
The Great Oxidation Event. The first introduction of oxygen into the atmosphere 2.5 BILLION years ago. All due to photosynthesis from cyanobacteria, little, marine, bacterial plants. Before this, any oxygen which happened upon Earth was dissolved into iron or organic matter, but once they became saturated, oxygen eventually grew in number. Now, before oxygen, bacteria were anaerobic, meaning they lived without air. However, as they were not used to oxygen, it was toxic for them, and they got wiped out (Bit hard to avoid poison when it is literally EVERYWHERE, isn’t it? Quarantined people cannot agree more!). Oxygen also reacted with methane and reduced its concentration, making the planet colder and triggering an Ice Age (again), called the Huronian, which lasted 300 million years (Didn’t tell you there were two, did I?).
As for life, no more were there hard-shelled bacteria, but rather soft-bodied Protista, fungi, and many others. One of the most important was Bangiomorpha pubescens, a species of red algae, which was the first plant to genetically reproduce, instead of making a clone of itself. It may still be alive. However, there were many creatures who only lasted a few million years and died out later. Like the Charnia, an animal which resembled a fern, but lived deep in the ocean, well below the level of photosynthesis. It was the first animal to reproduce genetically. Others existed, though most looked like rocks. All the animals in this eon stayed anchored in one place all their lives, except for the Nemiana Simplex, an ancestor of the jellyfish who may have fed on algae. I guess I can pull a moral from this: Do not stay rooted in one place or do the same thing over and over; or else you’ll die out. (Not the cheeriest moral.).
Shaurya Prasad (Grade 7 )