Musiclover's+Cambrian+Period

__The "Explosive" Cambrian Period__ 544 - 490 million years ago

**Precambrian Time:** Nobody was there to see the universe form but from what scientists believe, it started off with the big bang. What happened on Earth after the big bang, though? The first chunk of time on Earth was called Precambrian time. During this time, the first bacteria and the first animals appeared on Earth. Also the first oceans and ice ages came into existence. Precambrian time was basically the beginning of everything, even oxygen!

**Cambrian Period:**

The next chunk of time was called the Paleozoic era, and this era was divided up into shorter chunks of time named periods. The beginning of the Paleozoic Era was the Cambrian Period. This period is where we see the evolution of the new animals on Earth. It happens so fast that they named it the “Cambrian Explosion” because of how rapid we saw diversity in animals. Other than seeing all these new animals, we also see their ways of communicating with each other. Something else going on at this time is that the weather is warming up, causing ice sheets to melt, and the sea level to rise. After the Cambrian Period comes the Ordovician Period and then the Silurian Period.

**Silurian Period:**

The Silurian Period is just like the Precambrian Time and the Cambrian Period in the sense of seeing new life forms and also life forms that are developing. In this period, we continue to see vertebrates in underwater animals like fishes. Specifically, jawless fish are continuing to evolve. We also see the first plants growing and the coral reef developing. Not much else happened in this time period, but there is definitely a lot more happening in all the time periods after this one.

**Abiotic/Landforms:**

The continents today have all relocated over the years, but back in the Cambrian Period, which was 544 million years ago, the continents were all mashed together. They named it super continent Pannotia and it was closest to the South Pole. Eventually, Pannotia broke up into pieces. The newly formed continents were called Laurentia, Godwana, Siberia, and Baltica. Laurentia was made up of North America (where Massachusetts is!) and Canada. Godwana, the largest continent at the time, was made up of today’s southern continents. Siberia and Baltica were made up of Scandinavia, Eastern Europe, and European Russia. The rest of the land was not a part of a continent, but it lied in fragments on the North coast of Godwana. The southern hemisphere is where most of the world’s land was, as opposed to the northwestern side of the world, which had no land and only seas and ice shelves. That was one of the places where ice existed. At the South and North poles, there wasn’t as much ice as there is today because of the warm weather. As for the seas, they were warm as well and they covered land in some places.

How do we know that the Cambrian Period actually existed? We have evidence to prove it. During this time perio d, the continents are forming and moving all around. Perhaps when the sea level rose and covered some land, there were animals in that sea that became fossilized in the land. What we know for certain is that these rocks and fossils are still on land and located all around the world- hundreds of millions of years later. Trilobites were one of the most common animals; therefore there are many fossils of them. One trilobite fossil named Cedaria Minor was found in Utah, USA. Another was found in Canada’s Yoho National Park. There have even been fossils of trilobites with no eyes! In addition to those places where fossils have been found, there are also places that are just bursting with evidence. A place near Marathon County in Wisconsin, USA named Blackberry Hill exhibits more of this evidence. Other fossils have been found in the Great Basin of western USA, Wales, northeastern USA, Scandinavia, and China.

**Biotic:**

The Cambrian Explosion was when a diversity of animals appeared on Earth all at the same time, almost like an explosio n created and spread out all these new animals across the entire sea. Of course, the animals weren't really created from an explosion, they have evolved from the single celled animals from the Precambrian Period. Aside from that, there was a specific family of animals named the arthropod family, which was dominant during the Cambrian Period. This family created a new strategy for survival. They were able to take some chemicals in the water and use them to make hard shells to protect themselves. An example of members of the arthropod family would be trilobites, the ancient ancestors of crabs, and also one of the most common animals at this time. Scientists today think that there may have been over 10,000 different species of trilobites. These trilobites were invertebrates, as well as the rest of the arthropod family. They all had shells, but no bones. The first ever vertebrates, animals with bones, were fishes. Other vertebrates at this time were sea scorpions, lobsters, lancelets, and the brachiopod family. Lancelets were the ancestors of jawless fish and the brachiopod family included animals with two shells, sort of like clams, that live in cold water and have hollow feeding tentacles. Bivalves are animals in the brachiopod family. New life forms included early jellyfish, sponges, and echinoderms (starfish-like organisms). These were all invertebrates, just like the worms and insects. Two very tiny organisms were wiwaxia and graptolites. Wiwaxia were spiny creatures and graptolites were wormlike creatures with tentacles. The only plants during this time period are algae-red, green, and brown, but that's not what the animals ate. They looked for particles that they could consume while also looking for shelter along the sea floor. They would also eat other animals if they could. All these animals continued developing all throughout the next time periods.

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