Carlos Isaac Monsalvo Jasso #11 11A
Click on the name and you’ll be taken to the Era, feel free to click the periods and it
should take you there.
Paleozoic Era Cenozoic Era
* It takes over 650 – 544 millions of years ago.
During this time, 90% of Earth’s history occurred
* Anaerobic structures appeared with
photosynthetic methods, adding oxygen to the
atmosphere and allowing evolution.
*There are few fossils since animals were soft
bodied, and during this time life only existed in the
* This period was from 544 to 290 millions years ago.
* Early in the Paleozoic Era, fossil record became
rich with evidence of many types of marine life.
* This fossil evidence shows that life was highly
diverse by the first part of the Paleozoic Era.
* This era is divided into 4 periods: Cambrian
Period, Ordovician & Silurian Periods, Devonian Period
and Carboniferous & Permian Periods.
* According to Paleontologists, this is the
period in which diversification of life
existed, “Cambrian Explosion”.
* In this period, organisms finally had hard
structures (shells and exoskeletons).
* In this period there were invertebrates like
jellyfishes which drifted through the
water, crawled in the surface or attached
themselves to ocean floors; trilobites were
common as well.
Ordovician & Silurian Periods
* Fist vertebrates to appear were jawless
fishes. During these periods, the ancestors of
modern octopi and squid appeared.
* Some animals in this time grew to the length of
* During these periods, insects
appeared, plants evolved and grew low to the
ground in damp areas.
* Several plants during this period adapted to
drier areas, which enabled them to invade more
* In this period many groups of fishes were
present in the ocean; and sharks appeared in the
* During the Devonian period, animals began to
invade the land. Some fish developed the ability
to crawl on leg like fins and eventually evolved
Carboniferous & Permian Periods
* During this period, life expanded over Earth’s
* Several animals evolved from amphibians (i.e.
* Remains of ancient plants formed deposits of
sediment that became coal.
* At the end of the Paleozoic era, many organisms
died due to a mass extinction: 95% of the complex
life in oceans disappeared.
* It lasted about 180 million years ago.
* During this period there was an increasing
dominance of dinosaurs. The Mesozoic Era is
marked by the appearance of flowering plants.
* This Era was divided into three periods: Triassic
Period, Jurassic Period and Cretaceous Period.
* Organisms that survived the mass extinction
became the main forms of life early in this
* Important organisms that survived:
fishes, insects, reptiles and cone bearing plants.
This era is commonly called “Age of the Reptiles”.
* About 225 million years ago, the first dinosaurs
appeared, and the first Mammals appeared at late
Triassic period, which resembled mouse or shrew.
* Dinosaurs became the dominant animals on land in
* Dinosaurs “ruled” for about 150 million years but
there were different types in different times.
* One of the first birds appeared during this
time, which made paleontologists think that birds
are relatives of dinosaurs.
* Reptiles still were the dominant vertebrates
throughout this period.
* Meat eating dinosaurs dominated land
ecosystems, while flying reptiles and birds soared
* The Cretaceous period brought new forms of
life: leafy threes, shrubs, and small flowering
plants which produced seeds.
* There was another mass extinction, which wiped
half of all plant and animals groups, including
* This era lasts from 65 million years ago to
* During this era, early mammals competed with
dinosaurs for food and places to live.
* During the Cenozoic era, mammals evolved
adaptations that allowed them to live in various
* This era is often called the “Age of Mammals”.
* This era is divided into two periods: Quaternary
Period & Tertiary Period.
* Earth’s climate was warm and mild.
* In oceans, marine mammals like whales and
dolphins evolved; on land, flowering plants and
insects flourished, providing food source for
* Some mammals became very large during this
* Mammals that had evolved in the Tertiary
Period had to face a changing environment during
* In this period, Earth’s climate went into a series
of ice ages.
* About 20.000 years ago Earth’s climate began
to warm up, melting glaciers over time.
* During this time, the Homo Sapiens might have
evolved as early as 100.000 years ago in Africa.