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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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