An Intro. . .

The earth is about 4.5 billion years old, but life could not live on it from the beginning. It took a whole billion years for the earth to cool after its creation and reach the point where it could have life. This initial life and the life which followed it are nothing close to the life we have now. There are four eras in the earth's history of life that lead to our present day.

The Precambrian Era

Started 542 million years ago.

This was the first era of life on earth. It makes up 87% of the earth's history.

During this era, specifically 2.7 billion years ago, organisms developed the ability to photosynthesize starting the process of oxygen creation. This filled the ocean's waters with oxygen. It also started filling the "sky" with oxygen too. Without these ancient bacteria developing this ability, we would not have most of the life we do now. After this though, a long ice age breaks out.

Cambrian Period

End: 485 mya (million years ago)

After the ice age concludes though, life has still maintained itself in the sea.

The Cambrian Explosion then occurs. This is when there was a burst of diversification when it came to plant and animal life. The first fishes and chordates developed during this time. Vertebrates and Invertebrates started developing too. The Pikaia was the first organism to have a spine.

Some more organisms that lived during this long era are: bacteria, sponges, sea anemones, corals and jelly fishes. Most of the fossils of the extinct organisms which lived during this era seem weird to us now.

Precambrian Vocab:

Organisms: A single living thing.

Photosynthesis: The process of where organisms use sunlight to make food from carbon dioxide and water.

Cambrian Explosion: The period when most major animals appeared in the fossil record.

Vertebrate: Organisms with a spine.

Invertebrates: Organisms without a spine.

The Paleozoic Era

Start: 488 million years ago

End: 250 million years ago

The Paleozoic Era life diversified with many animals and plants; not as much as during the Cambrian Explosion, but they sure did!

Some organisms that lived during this long era are: sea anemones, sea stars, worms, orthropods, amphibians, and corals.

Ordovician Period

 Start: 488 mya End: 443 mya

There is a sudden diversification of metazoan families during this period. Life is definitely still confined to the oceans. Other than diversification of the organisms in this era, not much else happened.

Silurian Period

Start: 443 mya End: 416 mya

First vascular land plants are seen now in this era. Most of the land during this period is very close to sea level and the water levels were rising. Other than the new land plant life not much happened in this period.

Devonian Period

Start: 419 mya End: 359 mya

The first amphibians develop and jawed fishes diversify. During this period the Tiktaalik evolved onto land. Tiktaalik would eventually evolve into reptiles too. All vertebrates are said to originate from it.

This period is also sometimes called the "Age of Fishes" because of the variety of fishes in the oceans.

Carboniferous Period

Start: 359 mya End: 299

The first reptiles were seen in this period thanks to the Tiktaalik evolving onto land in the previous period. Insects were also the size of birds. Trees and seed ferns developed during this complex period too. This period is famous for its swampy nature. It was very humid and wet in this environment.

These swamp trees, after dying, will produce our coal. This is where the period got it's name.

Permian Period

Start: 299 mya End: 250 mya

Reptiles continued to diversify in this period. However, at the end of this period the largest mass extinction occurred. 90% of marine life and 70% of land life went extinct. This was called the Permian Extinction.

Paleozoic Vocab:

Tiktaalik: First animal to evolve onto land.

Amphibians: Small vertebrates that need water to live.

Evolve: Changes in characteristics over long periods of time in a species.

Carboniferous: Producing or containing carbon or coal

Reptiles: Amphibians- but their skins are covered with plates, scales, etc.

Permian Extinction: Largest mass extinction

Mesozoic Era

Start: 250 million years ago

End: 66 million years ago

Dinosaurs, mammals and birds developed during Mesozoic Era. Dinosaurs evolved from reptiles.

During this era Pangea goes from its normal joined state to a slightly fractured one, showing that the continents will start moving apart due to plate tectonics.

Triassic Period

Start: 251 mya End: 199 mya

The first mammals and dinosaurs lived during this period. The ocean's organisms from the Permian period were still diversifying. Flying reptiles also took off into the air during this time. This period ended how it started, with many volcanoes, but the dinosaurs still went on into the Jurassic Period.