This is a chart showing the Earth's Geological Time Periods, but I am only telling about the plant and animal life that evolved during these times. If you wish to learn about how the Earth was changing at the same time, please see The History Of The Earth section. Remember one thing, these periods are not to scale in any way! Earth's periods and eras were really big, with the earliest eras being the largest. If you wish to see what they'd look like to scale, click here. The history of the Earth dates back billions of years, but life did not show up until about a billion years ago. This table starts at the Cambrian Period, but life really evolved in Precambrian times, which preceded the Cambrian. The first era was the Azoic era, which was not divided into periods and did not have any life.

Era	Period	Age	Information
P a l e o z o i c	Cambrian	570 million - 500 million years ago	During this period, all life existed only in the sea. There were no vertebrates (Organisms with a backbone) so the most advanced forms of life were snails and other small shelled organisms. The dominant species in this period were the trilobites, a now extinct species. Other creatures in this period included primitive snails, molluscs, and brachiopods. The only plants that existed were simple seaweeds in the water, and lichens on land.
	Ordovician	500 million - 435 million years ago	The very first vertebrates appeared in this period, but they were only the simplest of fish. However, they would someday evolve into the biggest, most advanced species on Earth. The largest animal of this time was a mollusc that had a shell of about 3 metres long. The plants in this period are the same as in the Cambrian.
	Silurian	435 million - 410 million years ago	One of the only great accomplishments of this period was the first breathing animal. Fossils of this scorpion have been found in Great Britain. Also, the first evidence of vascular plants (plants with tissue that carries food) comes from this period. They were only very simple plants, without even stems or leaves.
	Devonian	410 - 360 million years ago	By this period, fish had become the dominating life form. The sharks had already evolved, as well as lungfish and armoured fish. There were also the ancestors, and early forms of, amphibians. Also, this time was home to the very first insect. Also, plant life really took off. The first wooded plants appeared, along with ferns, scoring rushes, and scale trees. Fossil records show that there were forests in this time.
	Carboniferous	360 million - 290 million years ago	The first part of this period was sometimes called the Mississipian Period. A lot of the life here was the same as in the Devonian. A group of sharks called the Cestraciontes, or shell crushers, were the dominant marine species. The dominant land animal was the Stegocephalia, a lizard-like amphibian. They evolved from the Lungfish. The trees in this period grew larger and stronger than in the last. The second part of this period is sometimes referred to as the Pennsylvanian Period. This part was very important, because the first Reptiles evolved. Reptiles live entirely on land. Some other species were spiders, snails, scorpions and cockroaches. There was also a dragonfly with a wingspan of 74 cm, the largest insect that ever evolved. The largest trees were the scale trees, which grew 1.8 metres in diameter and 30 metres high, along with the first true conifers.
	Permian	290 million - 240 million years ago	The Permian period was the last period of the Paleozoic Era. The very important events of this time were that the marine animals that once dominated the planet were starting to fall back, with reptiles taking over. Since this was the last period before the dinosaurs, the reptiles were really evolving fast and strong. Another very important even was the appearance of a certain type of reptile, called the Theriodontia. They were the ancestors of all mammals. By this time, life on Earth had pretty much taken off, and was preparing for the rule of the giant lizards called dinosaurs.
M e s o z o i c	Triassic	240 million - 205 million years ago	Probably the most important thing that happened in this period was the appearance of the dinosaurs. Triassic dinosaurs were small creatures that ran on their hind feet and seldom grew over 15 feet high. In the waters, the Ichthyosaurs began to appear, and a group of flying reptiles, called the Pterosaurs, began their rule over the sky. Another very important stage of development was the evolution of the first mammals. They were small and resembled lizards, but, even though the inferior race of the time, they possessed something that would one day allow them to rule the planet. (Muhahah!) Also in the sea, the first ancestors of modern bony fishes, the Teleostei, appeared. The vegetation was made up of evergreens, ginkgoes, conifers and palms.
	Jurassic	205 million - 138 million years ago	Yah! Jurassic Park! Whatever. The dinosaurs continued to evolve into very diverse species, including most of the dinosaurs we know and love. The Sauropods appeared, which included dinosaurs such as Apatosaurus and Brachiosaurus. The cool carnivorous dinosaur of the time was Allosaurus, and Stegosaurus led the armoured dinosaurs. Of the Pterosaurs, the Pterodactyl appeared, which could have a wingspan of up to 1.2 metres during this period. The very first bird, called an Archaeopteryx, evolved. It looked liked a dinosaur with feathers, and was probably unable to fly, just glide. The marine life was real scary. There were such animals as the Plesiosaurs, which looked like sauropods with flippers, the Ichthyosauria, which looked like evil dolphins from hell, and early crocodiles. The mammals had become more popular, but none were any larger than dogs. They were real sick of being stepped on by the dinosaurs. Some of the insects were moths, flies, beetles, grasshoppers, and termites, while the shellfish were lobsters, shrimp, and ammonites. The vegetation was dominated by Cyads. The climate in the whole of the Earth was warm and mild.
	Cretaceous	138 million - 65 million years ago	The dinosaurs were still the dominating form of life, and all the types of dinosaurs that were around in the Jurassic were here too, with the addition of the horned dinosaurs. The largest of the pterodactyls had a wingspan 0f 15 metres! On a much smaller scale than the dinosaurs, but still important, were the first snakes and lizards. Many other types of birds appeared, and even though they were more modern than the Archaeopteryx, most of them were still unable to fly. The mammals of this period included the first marsupials, and the first crabs also appeared in the sea. A very important advance in the plant kingdom was the evolution of the deciduous trees, and a lot of tree species we know today first arrived during that time. Suddenly, at the end of this period, all the dinosaurs on Earth swiftly and mysteriously disappeared.
C e n o z o i c	Tertiary	65 million - 1.6 million years ago	The two periods in the Cenozoic Era are divided into epochs because we know so much about them. The first epoch in the Tertiary Period is the Paleocene. it lasted from 65 million to 55 million years ago. In this time, mammals were just starting to evolve. They were all small, with none being any bigger than a modern bear, and not very smart. Even though there were seven groups of mammals in the Paleocene, only four have survived until present day. The marsupials, the insectivores, the primates, and the rodents. The Eocene Epoch lasted from 55 million to 38 million years ago. In this epoch, the ancestors of such animals as the horse, rhinoceros, camel, rodent, and monkey evolved, but they were all small and primitive. Also, the first aquatic mammals, the ancestors of whales, appeared, along with modern birds such as eagles, pelicans, quail, and vultures. The next epoch was the Miocene. In this epoch, something happened that would change the development of mammals forever. The first grasses appeared. This brought with it the appearance of grazing animals such as horses, camels, and rhinoceroses. They became very common. The Mastodon also evolved, along with a gorilla-like ape called Dryopithecus. Carnivores such as cats and wolflike dogs were also common. The Pliocene epoch is very similar to the Miocene, but is looked upon as the climax of The Age Of Mammals. It lasted from 5 million to 1.6 million years ago.
	Quaternary	1.6 million years ago to modern time	All of the animals that we have today came during this period, including ourselves, the humans.