There are two major uses of the word Evolution.
The first one in simple terms would be the
"increase in complexity"
Another one I would define as
"change over time"
One can characterize them as a Ladder, and as Tree respectively.
The Ladder was the primary use for the longest time,
even today people often refer to Evolution in terms of a Ladder,
and correctly so.
Many concepts in science and philosoply have been painted as a Ladder of complexity
Only after a hypothesis presented by Charles Darvin gained traction,
the "change over time" meaning to Evolution have been adopted to describe the diversity of life.
Previously also seen as a Ladder.
In modern day biological sciences the word Evolution usually refers to "change over time" rather than "increase in complexity". Although, it is not uncommon to use a concept of Ladder.
An example of the Ladder in biology would be a idea of Abiogenesis.
Abiogenesis is a hypothesis put out there which states that gradual increase in complexity of naturally occuring chemical reactions can eventually cause Life to emerge.
Life of course is defined as system which is
-built off of units, such as Cells,
-is capable of Reproduction,
-have it's own Metabolism,
-responds to it's environment,
-and adapts to changes of it's environment
Consequently, Viruses, are not "alive" as they do not have Metabolism.
A simplified model of Abiogenesis would look as follows:
- Simple Ribonucleotides, and Amino Acids Synthetize in the environment
- Ribonucleotides assemble into shorter and longer chains of RNA
- Certain RNA sequences have stronger or weaker catalytic activity
- Some RNA sequences catalyze modifications on other RNA chains, and Amino Acids
- Some RNA gain ability to create Peptidic Bonds between Amino Acids
- First Proteins form
- Pockets of microenviromment a kin to cells emegre, likely in pores of vulcanic rocks
- Proteins can perform more complex catalytic reactions than RNA
- Ribonucleoides, Amino Acids, Deoxyribonucleotides, and simple Lipids can be synthetized
- Means of RNA replication emerges
- Lipids form cell-like protective membranes providing new fund "life" with means of expanding
- DNA emerges
- DNA replication emerges
Finally, First Living Cell
Once we're talking about "Life",
that's where we can discard the idea of a Ladder and we need to start thinking in terms of a Tree.
So what is a Tree of Life?
It's an allegorical representation of relationships between all living organisms which Evolved from a single "seed", being the common ancestor.
Every year, there is a new set of leaves which grew in spring.
These leaves represent the idea that in given moment, all living organisms are "Equally Evolved".
The Shape of the Tree changes from year to year.
Which represents the Change over time.
Branches, stems, and twigs connecting to one another indicate the proximity of relationships between individual organisms.
Image Source
As for graphical representation of the Tree of Life, a Circle makes a much clean, simple version.
But the principle is the same.
In part 2,
we will discuss the modern synthetic theory of Evolution
This post is just one in a serie called Lil' Science Dictionary.
The purpose of the serie is educational in nature,
created to explain in simple terms certain scientific concepts.
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