World History

World history timeline is divided in each age represents Earth's timespan by million years ago (MYA).

• Precambrian period, that single celled organisms like blue-green algae and bacteria first appeared. The first multicellular, soft bodied animals began to emerge such as jellyfish, seapens, and worms.

• The Cambrian period was characterized by a diverse eruption of life in the seas. Life had not yet evolved on land. The highest forms of life existing at this time were the trilobites, which reached lengths up to two feet. Green and red algae started to appear as well as sponges, gastropods, and segmented worms.

• During the early Ordovician period the first vertebrate fish have been found. Graptolites and corals also flourished.

• Silurian period sees the appearance of the first plants on land. Algae is in abundance in the seas, as well as marine invertebrates.

• As the Paleozoic era continues, we see the first appearance of land creatures, such as mites, ammonites, crabs, ground insects, and spiders.
Towards the end of the Devonian period, amphibians began to colonize the land. The first ferns also grew and true seed plants eventually emerged. The Devonian period also saw many new groups of fish evolve.

• Carboniferous: During this period snakes emerged as well as salamander type amphibians. Large amphibians roamed the lands now and fresh water fish and sharks were now in abundance. Near the end of this period the first reptiles appeared on land.

• The Permian Period, at the end of the Paleozoic era, marked a great changes in the Earth's climate and appearance. Trilobites and other marine groups became extinct, and a group of small reptiles abound. These were the ancestors to most modern reptiles and the ruling dinosaurs as well as pterosaurs and crocodiles. Thriving also, were the early ancestors to mammals (synapdia), which included some large reptiles such as dimetrodon. Reptiles grew to dominance among vertebrates, because their special adaptations enabled them to flourish in the drier climate. The warm zone spread in the northern hemisphere, where extensive dry desert appeared. The rock formed at that time were stained red by iron oxides, the result of intense heating by the sun of a surface devoid of vegetation cover. the old types of plants and animals died out.

• As the Triassic era begins, we see the rise of the what is known as the dinosaurs. Pterosaurs (flying reptiles) also made their first appearance here as well as frogs, turtles, and crocodiles.

• In Jurassic period began the Age of the Ruling Reptiles. During this period, vegetation was greener and more lush. By Late Jurassic, huge dinosaurs such as Stegosaurus, Ceratosaurus, Brachiosaurus, and Allosaurus walked the lands. Flying reptiles ruled the skies. The earliest known birds also appeared.

• The Cretaceous period of the Mesozoic era may have seen more dinosaurs then ever before. The horned Cretaceous dinosaurs appeared, like the Triceratops and Centrosaurus. The armored Ankylosaurus, duckbilled Parasaurolophus, and large carnivore Tyrannosaurus were a few of the quickly evolving dinosaurs. Birds became increasingly numerous & flowering plants were emerging. By the end of the Cretaceous period, all large and small ruling reptiles, except the crocodile went extinct.

• Paleogene : Part of the Cenozoic era, the Tertiary period is divided into five epochs: Paleocene, Eocene, Oligocene, Miocene, and Pliocene. During this time mammals diversified quickly. Some examples are marsupials, insectivores, bears, hyenas, dogs, cats, seals, walruses, whales, dolphins, early mastodons, hoofed mammals, horses, rhinoceroses, hippopotamuses, oreodonts, rodents, rabbits, monkeys, lemurs, apes, and humans (Australopithecus).

• Neogene period was the second and last period of the Cenozoic era. Quaternary period is divided into two epochs: Pleistocene and Holocene. Mammoths roamed the lands. Cattle, deer, and of course, Homo habilis, Homo erectus, and Homo sapiens.