Era: Precambrian
Period: no period
Time: Birth of Earth to approximately 600mya.
The Precambrian makes up about 87% of Earth’s History! During this era most organisms were simple unicellular
(one-cell) plants and animals living in the sea. Bacteria were also abundant. By the end of the Precambrian, the
first simple multicellular (many cells) organisms, like jellyfish and sponges, started to appear in the oceans.
Era: Paleozoic
Period: Cambrian
Time: 590 – 492mya
During the Cambrian period, a burst of life occurred. Fossils show the appearance of hundreds of new multicellular
plants and animals in the oceans in a short amount of time, in what is now known as the “Cambrian explosion”.
Most of these new organisms eventually went extinct, but some survived and evolved. Fossils also show the
appearance of simple fish for the first time.
Era: Paleozoic
Period: Ordovician
Time: 491 – 445mya
Fish become very common in the oceans of the Ordovician. Simple plants like mosses began colonizing land,
followed by fungi.
Era: Paleozoic
Period: Silurian
Time: 443 – 418mya
The Silurian was the Age of Fish! Fishes dominated the oceans. The first complex plants capable of
photosynthesizing began to colonize land, forming primitive forests.
Era: Paleozoic
Period: Devonian
Time: 417 – 355mya
In the Devonian, the fish continued to dominate the oceans. The first sharks appeared. Land plants continued to
evolve, producing oxygen through photosynthesis. Thanks to this oxygen, the first amphibians began to leave the
water and walk the land.
Era: Paleozoic
Period: Carboniferous
Time: 354- 295mya
Amphibians very common and fossils suggest that the first early reptiles appeared. Insects appeared and become
abundant too. Fossils show that the Earth was covered in huge tropical forests. When this plant matter died it
formed the large deposits of coal and oil that we use nowadays for transport and production of electricity.
Era: Paleozoic
Period: Permian
Time: 290 -250mya
During the Permian, mosses and ferns became abundant. Reptiles and amphibians were also abundant, including
advanced reptiles that begin to show mammal characteristics like warm blood, fur and live-birth. Unfortunately, at
the end of the Permian a mass-extinction event, the biggest in the history of Earth, happened: approximately 96%
of all life on Earth was killed, possibly by extreme changes in climate.
Era: Mesozoic
Period: Triassic
Time: 249 – 210mya
The Triassic marks the beginning of the Mesozoic Era. After the mass-extinction of the Permian there was plenty
of living space for new plants and animals to take over. The first early dinosaurs appear and began to spread out.
Also, the first early mammals appeared.
Era: Mesozoic
Period: Jurassic
Time: 206 – 145mya
The Jurassic was the age of the dinosaurs, but even though they dominated they were not the only ones: the first
early birds also appeared. Weather was generally warm, and plants like cycads, yuccas and palm trees were
common in warm parts. In the cooler parts of the planet, pine forests dominated large areas of land. Flowering
plants (those that produce flowers) first appeared during this time, quickly spread around the Earth, and soon
became the dominate plant group. They still are!
Era: Mesozoic
Period: Cretaceous
Time: 144-67mya
The Cretaceous marked the end of the Mesozoic, and the end of the dinosaurs! A massive extinction event killed
most of the dinosaurs, but many mammals, birds, fish and amphibians survived. In total, approximately 65% of all
animal and plant species disappeared. Scientists believe that this mass extinction was produced by a meteorite
falling on Earth.
Era: Cenozoic
Period: Tertiary
Time: 65- 1.8mya
During the Tertiary the weather on Earth was cooled a lot. A very important organism appeared: grasses. This was
very important, because a lot of animals eat grass. Mammals now become very abundant (no more dinosaurs to
hide from), and some of them grew to huge sizes! Some of the more characteristic mammal groups, like whales
and monkeys, appeared at around this time. The very first early humans appeared.
Era: Cenozoic
Period: Quaternary
Time: 1.7mya to present time
The most important events during the quaternary where the various Ice Ages that happened: cold periods (ice
ages) alternating with warmer periods (interglacial ages). As the Earth became colder and snow-covered, animals
that could survive the cold, like mammoths, bears and sabre-tooth tigers survived. Modern humans finally
appeared. During the final stages of the Quaternary the Earth warmed up, and the majority of the great land
mammals (mammoths, giant sloths, sabre-tooth tigers) went extinct. We are currently in the Quaternary, living in
an interglacial period.