Do you want to learn about the beginning of life on earth? Well, then we have to start with the first era- the Precambrian. The Precambrian Time started with the formation of Earth, 4.6 BYA(billion years ago,) and ended 545 MYA (million years ago.) The climate of the Precambrian varied throughout the different periods of the era. In the later Precambrian the climate went from very warm temperatures to very cold temperatures. The cold periods were so long, there were glaciers found near the equator! Now, that you know about the climate, you'll probably be wondering about the actual earth. The continents in the Precambrian Time were very different from the shape of the continents today. Lets back up for a second. After the formation of the earth, the planet was just a round ball of dried rock, too hot for water to accumulate. After the second atmosphere was formed, the earth started to cool down, and water started to collect in dips on the earth’s surface. The continents stuck out of the single, enormous ocean, as a supercontinent, 300 MYA. When I say that they were a *supercontinent* I mean that they were all connected to one another as one big, huge continent. Most of the supercontinent was found below the equator, but there were parts of Southern and Northern China, Arabia, India, Antarctica, and Australia, that were all above the equator. Overtime, erosion, sedimentation, and volcanic activity eventually created small proto-continents, which slowly grew to roughly the size they are today. this was about 2.5 BYA. Now that you know about the continents, we’ll start to learn about life in the Precambrian. At the beginning of time, there was nothing but rock and water. At about 3.4 BYA, the first forms of bacteria show up in the fossil record. Soon after, the microscopic, single-celled organisms started using solar energy to create their own food, also known as the process of photosynthesis, which would later lead to the earliest simple plant forms. At about 600 MYA, the first multi-celled organisms appeared in the fossil record. These early critters fall into 3 categories, the sponges, the cnidarians, and the annelids. Sponges are multi-celled organisms without organs or nerves systems. Cnidarians are creatures with simple digestive systems. This family includes corals, jellyfish, and sea anemones. Annelids are fluid-filled body cavities that breathed through their skins. At the end of the period the single-celled algae, called acritarchs, and Ediacaran animals all disappear from the fossil record during the end of the Vendian period. When these single-celled organisms and soft-bodied animals disappear, scientists blame the changes in sea levels and a decrease in oxygen levels. This mass extinction was rated a “3,” which is considered the lowest on a scale of 1-3, 3 being the lowest, and 1 being the highest intensity. Now you know all about the Precambrian Time.