microfossils from Bulawayo Region (South Rhodesia) and the Transvaal Series
(South Africa). Their age was determined to be in the limits of 2.8—2.2 bln.
years.
The problem of whether prior to the period of the late archaic epoch
photosynthesis has occurred with the release of molecular oxygen or via
the mechanisms of methanogenesis, glycolysis or other routes of nitrogen
fixation without the release of oxygen remains unsolved.
The Gunflint Formation (southern part of Ontario, Canada and the
northern part of Minnesota, USA) gives a clue to the disclosure of the
“secrets” of the increased diversity of living organisms existing 2 billion
years ago. Except the bacteria and algae mentioned up to here,
ferrobacteria, multicellular thread-like structures, lower forms of fungi and
radial colonies are found in this formation.
A significant progress in the evolution of life has been registered in the
findings from the remains in the Beck Spring Formation (Eastern California)
aged 1.4—1.2 bln. years. Alongside the prokaryotes (bacteria and blue-green
algae) eukaryotes have also found (thread-like blue-green algae,
plankton green and yellow-brown algae). The presence of minimal
quantities of molecular oxygen (O₂) is also recorded which is conceived as
resulting from the then existing photosynthesizing organisms.
Following its natural course, evolution of life has arisen to new higher
forms of organization. The imprints of living organisms found in the formations
Bitter Springs (Central Australia) and the Grand Canyon of the Colorado River
(Arizona) testify to this development. These fossils show that in the Later
Riphean (1—0.9 bln. years) a transition from a haploid to a diploid form of
existence has taken place. Except the amitotic division cells in mitosis as well
as in meiosis (characteristic of the reduction division in sexual cells) were
observed. Sexual reproduction in eukaryotes has emerged.
The arising of the sexual process as a biological phenomenon marks
a new stage in the evolution of life. The mechanisms for exchange of
genetic material have become more diversified and the possibilities for
the creation of new forms as a result of genetic recombinations have
grown considerably. In the Early Cambrium (0.7—0.6 bln. years) higher
forms of life appear on the scene — multicellular algae, leaf-like and fern-like
stems, jelly-fish, coral-like organisms, worms and askeletal animals
(Metazoa). Well-preserved remains of such creatures have been found in
the Ediacara Region (Southern Australia), in the Russian and Siberian
Platforms, etc.
Let us stop up to here our “excursion” along the trail of life on Earth.
The “silhouette” of the cell and its evolution that have led to the stunning
diversity of living organisms is reflected on the background of a period of
approximately 3.8 bln. years. It is not the subject of this book to
contemplate on what future course evolution will take or what new forms
will emerge, in what direction the thus created Homo sapiens will develop