- about the Sea
consideration of the geological history of earth as it pertains to the genesis
and evolution of life, that is, to paleobiology, must hold the sea as centric.
Life began in the sea, and most extant life yet exists in the sea. The sea contains
an incomprehensible diversity of life, mostly still undiscovered or described,
ranging across all the domains of life. The sea is absolutely brimming with microscopic
life, including bacteria that make their living by a constellation of different
metabolic processes, and the Archaeans, among which are the extremophiles living
in vents at temperatures well above the boiling point of water.
sea was the mother of all life beginning some 3.8 billion years
ago, and remains so today. The land-based animals each carry with
them a miniature ocean, pulsing in their cells and circulatory
systems. All life, including human, could be viewed as containers
of sea water with the same mineral constituency as the oceans,
and a dynamic dispersion of molecules that perform the biological
processes that constitute life.
all living cells - proteins answer for both form and function.
Proteins are the active elements of cells that aid and control
the chemical reactions that make the cell work. They receive signals
from outside of the cell. They control the processes by which
proteins are made from the instructions in the genes. They also
form the scaffolding that gives cells their shape and as well
as parts of the linkages that stick cells together into tissues
and organs. A protein's shape determines its function, which,
in turn, depends on its water-hating (hydrophobic) properties
- to perform their biological functions, proteins must be immersed
in a miniature sea within the cell that does not greatly differ
from the sea from whence it came. Life came from the sea, and
the sea sustains life.
Time (4500 to 3800 mya)
Hadean is the geological time period during which Earth formed, from the start
of the solar system (4.6 billion years ago) until accretion, impact, and local
melting led to stable Earth-Moon orbits and the oldest Earth rocks (3.8 billion
is believed that the earth formed 15 billion years after the Big
Bang, and some 4 ½ billion years ago, a time span beyond
comprehension. It was some 4 billion years afterwards that animals
for the first time left their mark in the fossil record. It was
during this Precambrian period when profound events occurred,
leading ultimately to "life" as we know it today. From
4.5 to 3.8 bya (the Hadean) the earth was indeed a hellish (as
the name Hadean means, hostile place. During this period the sun
formed by gravitational compaction, and eventually reached temperature
and pressure conditions for nuclear fusion. Other particles coalesced
under gravity to form continually growing planets. The oldest
rocks on earth (3.8 bya) were formed through the cooling of the
theretofore, molten Earth.
Time (3800 to 2500 mya)
the period between 3.8 and 2.5 bya, the Earth's atmosphere comprised methane,
ammonia, and other gases which would be toxic to most life on our planet today.
The Earth's crust continued to cool, and rocks and continental plates began to
form. It is thought that life first formed during this period. The oldest known
fossils are bacterial microfossils that roughly date to 3.5 billion years ago.
Era (2500 to 544 mya)
than half of known Proterozoic rocks are sandstone-carbonate-shale
assemblages, suggesting their deposition along throughout the
Proterozoic along rifted continental margins. Massive sedimentary
rock formations comprised of alternating layers of silica (chert)
and iron minerals (mostly iron oxides - hematite and magnetite)
formed during the Proterozoic. This strongly supports early oxygenation
of the atmosphere atmosphere by photosynthizing cyanobacteria
by about 2.3 BA. The introduction of free oxygen into the atmosphere
and the worlds oceans caused the precipitation of dissolved iron
and silica thus forming the massive banded iron formations.
lack of fossils of hard-shelled organisms in the Precambrian makes
determination of paleo-geography of the earth essentially impossible
prior to about 650 MA. What is known supports the theory of the
formation of the oldest supercontinent, Rodinia some 1.1 BA, and
its subsequent breakup into two halves beginning at about 750
MA, forming the Panthallassic Ocean. The Upper Proterozoic earth
is thought to have been an ice-house, similar to present-day earth.
North America is thought to have formed the center of Rhodinia,
with the east coast of North America adjacent to western South
America and the west coast of North America adjacent to Australia
the breakup, North America rotated southwards towards the South Pole. The northern
half of Rodinia comprising Antarctica, Australia, India, , and the what would
ultimately become China rotated counter-clockwise and north across the North Pole.
components that formed the late Paleozoic continents of Pangea
(Laurasia and Gondwana) were evolving during the Upper Proterozoic.
A third continent called the Congo craton lay between the two
halves of Rodinia and comprised what is now north-central Africa.
Near the end of the Proterozoic, the three continents collided
to form a new supercontinent called Pannotia, resulting in the
Pan-African orogeny (i.e., mountain building event). Pannotia,
in turn, began to break apart at about 600 MA.
suggests that glaciers were more extensive on earth during the
late Precambrian than at any other time in geological history,
with much of the earth's land mass located at either pole.