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Paleozoic
(marine-life] era covers the next 250,000,000 years. |
1. The CAMBRIAN period
All life is under the sea during
this period.
Primitive marine animals are well
established and are prepared for the next evolutionary development.
Ameba
are typical survivors of this initial stage of animal life, having
made their appearance toward the close of the preceding transition
period.
| The higher protozoan
type of animal life soon appeared, and appeared suddenly. And
from these far-distant times the
AMEBA, the typical single-celled animal organism, has
come on down but little modified. He disports himself today much
as he did when he was the last and greatest achievement in life
evolution.
This minute creature
and his protozoan cousins are to the animal creation what
BACTERIA are to the plant kingdom; they represent the survival
of the first early evolutionary steps in life differentiation
together with failure of subsequent development. [732]
|
Ameba (top right) and protozoan
cousins
400,000,000 years ago marine
life, both vegetable and animal, is fairly well distributed over the
whole world. As this era begins, the sea bottoms, the extensive
continental shelves, and the numerous shallow near-shore basins are
covered with prolific vegetation.
Undersea vegetation, algae (seaweed)
Vegetation now for the first time
crawls out on land and adapts to a non-marine environment.
The first land plants, liverworts and
mosses
| Before
long the early single-celled animal types associated
themselves in communities, first on the plan of the Volvox
and presently along the lines of the Hydra and jellyfish.
[732]
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A Hydra Lesson
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* * *
390,000,000 years ago
suddenly
the first multicellular animals – the trilobites appear and dominate
the seas.
Trilobite fossils
present certain basic uniformities coupled with certain well-marked
variations that developed according to where they were originally
planted.
360,000,000 years
ago marine life consisted mainly of seaweeds,
one-celled
organisms, simple sponges, trilobites and other crustaceans—shrimps,
crabs, and lobsters.
A simple sponge
Three thousand
varieties of brachiopods appear at the close of this era.
 
2. The
ORDOVICIAN period
310,000,000
years ago the land plants well developed and migrating farther and
farther from the seashores, but few plant fossils of these times are
to be found.
Animal life consisted of
every type of life below the vertebrate scale, and all were marine
organisms, except for a
few types of worms
that burrowed along the seashores.
The trilobites were still
prominent,
tens of
thousands of patterns, predecessors of modern crustaceans.
Lime-secreting algae
was widespread.
There were ancestral
corals.
Sea worms were abundant
Many varieties of
jellyfish
appeared.
Corals
and the later types of sponges evolved.
Cephalopods were
well developed, consisting of the modern pearly nautilus, octopus,
cuttlefish, and squid.
Three were many varieties
of shell animals: gastropods included single-shelled drills,
periwinkles, and snails; bivalve gastropods embrace muscles,
clams, oysters, and scallops;
valve-shelled brachiopods
Next: Paper 60-
"Urantia During the Early Land-Life Era"
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