Cambrian Explosion: The Life Revolution

What was Cambrian explosion?

Cambrian explosion was an event that happened about 541 million years ago and lasted about 25 million years. It is when most phyla appeared, and resulted in appearance of many diverse species. It changed the ecology on Earth and was a big step to live we know today.

The beginning of revolution

First multicellular organisms appeared about 3 billion years ago, creating a great opportunity for life development. However, life needed over 2.5 billion years to use new possibilities in the revolutionary event called today the Cambrian explosion. It lasted between 20 and 25 million years and changed life on Earth forever. Although it seems logical, that that kind of change was triggered by some factor, though it is still uncertain what was it. Recent study suggest, that it was the formation of supercontinent Godwana. Some scientists link it with the extinction of Edicaran animals because Cambrian explosion started immediately after they had gone.

Precambrian organisms- Edicaran animals

What was the trigger?

Though we don't know the exact cause, environmental explanations suggest that before the Cambrian explosion conditions on Earth changed a lot. First, the level of oxygen increased, which was a turning point for multicellular organisms. It is possible, that it was because of increasing number of photosynthesizing organisms. On the other hand, the Snowball Earth hypothesis suggest that before Cambrian explosion the whole globe was covered with ice. When it melted, a lot more sunlight reached the water, temperature increase, and as a result new niches developed. However, the development explanation says that, when organisms created genes that were responsible for diverse body plans of organisms. That means, when the ancestor of modern animals was able to create a complex body plan, it provided so much material for further evolution, that the explosion of life began. And lastly, the ecological explanation suggest that organisms developed due to their ecological interactions.

life development during cambrian explosion

Almost all kinds of phylum with hard parts first appeared in the Cambrian period. In consequence of the very radical appearance of a wide variety of animals, new ecological mechanisms developed. Firstly, first predators appeared and the ongoing war between hunters and victim began. As a result, ecosystem became more complex that ever before, that led to faster evolution due to increasing competition. Moreover, organisms started occupying different marine habitats, adapting to new condition led to variety of shapes, sizes and lifestyles. Therefore, the complex ecological system of marine life as we know today developed. To clarify, new lifestyle that appeared were benethic lifestyle (leaving on a sea floor), and nektonic (organisms actively swimming). In addition, in the end of the period there was one more major change.

Image result for cambrian explosion
Cambrian Explosion: When Life Exploded

First organisms on land

In the late Cambrian period first organisms left their water homes and took up the land. Though the first vertebrates appeared 520 million years ago, it were probably arthropods, who conquered the land. Arthropods are phylum of invertebrate animals, that have exoskeleton. Among today's arthropods we can find insects, spiders and shellfish. The very first land organisms might be Euthycarcinoids - something between shellfish and insects. Soon after that Cambrian explosion ended and The Great Ordovician Biodiversification Event took over.

Euthycarcinoids may be first land animals
Credit: https://images-wixmp-ed30a86b8c4ca887773594c2

Evidence and importance of the Cambrian explosion

The direct evidences of Cambrian explosion are fossils, discovered all over the Earth. Firstly, mineralized skeletons are dated to appear during that period. The most typical records are "small shelly fossil", that are bone-like parts of animals. Unfortunately, we do not understand them, as a result many remain unclassified. Among other fossils we can find trilobites, and first land arthropods. Only organisms with skeleton-like structures fossilized, the rest dissolved over the years. However, there is still a lot to be explained as the research continues. Explaining Cambrian explosion is a dynamic study because it was the main event that led to live we know today. After it, plants and vertebrates came on land, and from that point the challenges of new ecosystem began. Organisms that could not adapt, did not survive

Trilobite fossil

Author's message

I hope this article make you understand how important the Cambrian explosion was for life on Earth. Please share the articles with your family and friends, and check out the links. In the next article we will discuss what happens to organisms that cannot adapt ti changes.

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