Life During the Paleozoic
Douglas Wilkin, Ph.D.
Jean Brainard, Ph.D.
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Printed: November 15, 2012
AUTHORS
Douglas Wilkin, Ph.D.
Jean Brainard, Ph.D.
www.ck12.org
C ONCEPT
Concept 1. Life During the Paleozoic
1
Life During the Paleozoic
• Give an overview of evolution during the Paleozoic Era.
What was early life like?
Prehistoric underwater life exploded with amazing new creatures during the Paleozoic Era. Evolution allowed life
to take many diverse forms, eventually developing the necessary adaptations to move from the ocean onto land.
Life During the Paleozoic
The Paleozoic Era is literally the era of “old life.” It lasted from 544 to 245 million years ago and is divided into
six periods. Major events in each period of the Paleozoic Era are described in Figure 1.1. The era began with a
spectacular burst of new life. This is called the Cambrian explosion. The era ended with the biggest mass extinction
the world had ever seen. This is known as the Permian extinction. At the following link, you can watch a video
about these and other events of the Paleozoic Era: http://www.youtube.com/watch?v=Bf2rrRmconU.
The Paleozoic Era
The Cambrian Period: Following the Precambrian mass extinction, there was an explosion of new kinds of
organisms in the Cambrian Period (544–505 million years ago). Many types of primitive animals called sponges
evolved. Small ocean invertebrates called trilobites became abundant.
The Ordovician Period: During the next period, the Ordovician Period (505–440 million years ago), the oceans
became filled with invertebrates of many types. Also during this period, the first fish evolved and plants colonized
the land for the first time. But animals still remained in the water.
The Silurian Period: During the Silurian Period (440–410 million years ago), corals appeared in the oceans, and fish
continued to evolve. On land, vascular plants appeared. With special tissues to circulate water and other materials,
these plants could grow larger than the earlier nonvascular plants.
The Devonian Period: During the Devonian Period (410–360 million years ago), the first seed plants evolved.
Seeds have a protective coat and stored food to help these plants survive. Seed plants eventually became the most
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FIGURE 1.1
The Paleozoic Era includes the six periods described here.
FIGURE 1.2
Two representatives of more than fifty
modern animal phyla from the Cambrian
explosion are reef-building sponges (left)
and early arthropods known as trilobites
(right). Both were abundant during the
Cambrian and later became extinct; however, the phyla they represent persist to
this day.
common type of land plants. In the oceans, fish with lobe fins evolved. They could breathe air when they raised their
heads above water. Breathing would be necessary for animals to eventually colonize the land.
The Carboniferous Period: Next, during the Carboniferous Period (360–290 million years ago), widespread forests
of huge plants left massive deposits of carbon that eventually turned to coal. The first amphibians evolved to move
out of the water and colonize land, but they had to return to the water to reproduce. Soon after amphibians arose, the
first reptiles evolved. They were the first animals that could reproduce on dry land.
The Permian Period: During the Permian Period (290–245 million years ago), all the major land masses collided
to form a supercontinent called Pangaea. Temperatures were extreme, and the climate was dry. Plants and animals
evolved adaptations to dryness, such as waxy leaves or leathery skin to prevent water loss. The Permian Period
ended with a mass extinction.
In the mass extinction that ended the Permian, the majority of species went extinct. Many hypotheses have been
offered to explain why this mass extinction occurred. These include huge meteorites striking Earth and enormous
volcanoes spewing ashes and gases into the atmosphere. Both could have darkened the skies with dust for many
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Concept 1. Life During the Paleozoic
FIGURE 1.3
Cooksonia,Cooksonia fossils measure
just centimeters in height and date from
the Silurian period.
FIGURE 1.4
On land, clubmosses, horsetails, and
ferns joined primitive seed plants and
early trees to form the first forests.
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FIGURE 1.5
The supercontinent Pangaea encompassed all of today’s continents in a single land mass. This configuration limited
shallow coastal areas which harbor marine species, and may have contributed
to the dramatic event which ended the
Permian - the most massive extinction
ever recorded.
months. This, in turn, would have shut down photosynthesis and cooled the planet. Despite the great loss of life,
there was light at the end of the tunnel. The Permian extinction paved the way for another burst of new life at the
start of the following Mesozoic Era. This included the evolution of the dinosaurs.
Summary
• The Paleozoic Era began with the Cambrian explosion. It ended with the Permian extinction.
• During the era, invertebrate animals diversified in the oceans. Plants, amphibians, and reptiles also moved to
the land.
Practice
Use the time slider in this resource to answer the questions that follow.
• Evolution at http://johnkyrk.com/evolution.swf.
1.
2.
3.
4.
5.
6.
4
When did the Paleozoic Era begin?
The Paleozoic Era began with what event?
What animals formed during the Cambrian explosion?
Describe 4 significant events during the Ordovician period.
Describe 4 significant events during the Silurian period.
Describe 5 significant events during the Devonian period.
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Concept 1. Life During the Paleozoic
7. Describe 2 significant events during the Carboniferous period.
8. What may have caused the mass extinction at the end of the Permian period?
Review
1. List three important evolutionary events that occurred during the Paleozoic Era.
2. Describe Pangaea.
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