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an emergent
website design
by
peter jay stein, md, ma
atmosphere
asthenosphere
lithosphere
regolith
biosphere
hydrosphere
This 54 page synopsis of the evolution
of the Earth, the origin and progression of life, and the
emergence of humans as descendants of the hominin lineage, divides the last 4.57 billion years into progressively overlapping, imagistic, time segments, to outline our place in biological existence.
magnetosphere
ionosphere
NINE
Emergent Life II
A Proposed Origin Of Life On Earth:
from protobionts to living cells
adapted from Biology, 2015, tenth edition, pp. 439-446
the pre-cell:
an internal energy source is
coupled to
chemical reactions
between
simple molecules,
enclosed within
a boundary,
to form a
self-sustaining,
increasingly
organizing
system
that must
grow
and
reproduce
AN RNA WORLD:
"...the first informational molecule to evolve in the progression toward a self-sustaining, self-reproducing cell...proteins and DNA...came...later...[is] self-replicating RNA molecules...[that] functioned as both enzymes and substrates for their own replication...", eventually catalyzing and facilitating peptide bond formation, and also eventually making double-stranded copies of itself (i.e., DNA) (Biology 2015, 10th edition, p. 442, 443).
vesicle-like assemblages
of organic polymers
promote the development of:
1) surface membranes of fatty acids and monoglycerides,
surrounding larger DNA-like molecules;
2) small, organic molecules, or nutrients, that can enter (diffuse) through the cell membrane;
3) larger DNA molecules that cannot leave the cell; and,
4) DNA, that with its double helix structure, is more stable/less reactive, than RNA.
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