It is here during the Precambrian age where it all began, the Earth, atmospheres and oceans formed creating the beginning of time.
The Precambrian age can be broken up into three zones: 1) Hadean Eon (the Earth formes) 2) Archean Eon (oceans and atmosphere form, earliest life forms appear) 3) Proterozoic Eon (sea plants begin photosynthesis) The Precambrian time covers a large bulk of the Earth’s History. It begins with the creation of the planets about 4.5 billion years ago and ends about 4 billion years later with the development of complex, multi-celled life-forms. |
The earliest living organisms
were microscopic algae and bacteria. As their numbers multiplied the need for an
alternative energy source grew. New varieties began to harness the power of the
sun through a biochemical process known as photosynthesis, a move that would
ultimately lead to simple plants. This created a chain reaction which opened
the planet up to animal life. About 3 billion years ago, Earth’s atmosphere was
completely oxygen free. That was until oxygen was released by the seas as a
by product of photosynthesis by cyanobacteria. Oxygen and gas levels began to
rise on Earth, breathing the life into more complex organisms. Not long after
this, the oxygen rich ozone layer was established, providing a shield of
protection against harmful solar radiation.
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Archaeologists can piece together
the past by examining the different layers of sedimentary rocks that have been formed
and laid down over millions of years. These rock layers contain a permanent
record of the past and evidence of the earliest life forms. The Precambrian age
is the earliest of the geological ages.
The Earth was already more than 600 million years old when life began. Earth cooled down from its molten state, and soon after this a solid crust and oceans had been created. Many scientists believe this was the catalyst for the development and emergence of the first cell membranes. With hot, mineral-rich volcanic vents, these seas gave rise to life. It is thought that bubbles formed self-replicating substances by attracting chemicals around them, over time combining to produce energy-using, living cells. These cells were known as Archaea. |
The first
multi-celled animals, known as the Ediacarans, emerged. These
creatures grew on the seabed and lacked any obvious heads, mouths, or digestive
organs.
The earliest multi-celled animals that survived the Precambrian fall into three main categories. The simplest of these soft-bodied creatures were sponges. Lacking organs or a nervous system, they lived by drawing water through their bodies and filtering out food particles. The cnidarians, which included sea anemones, corals, and jellyfish, had sac-like bodies and a simple digestive systems with a mouth. They caught food using tentacles armed with microscopic stinging cells. The third group, the annelids, had fluid-filled body cavities and breathed through their skin. |
It's thought the final stages of Precambrian time were marked by a prolonged global ice age. This may have led to widespread extinctions, mirroring the bleak endings to the geologic periods that followed.