Riddle Me This. #2

[center]I am the [b][c=7700B2]ever-changing[/c][/b] one,
My [b][c=004A59]origins[/c][/b] lost, my [b][c=008099]journey[/c][/b] begun.
Through [b][c=359E00]countless shifts[/c][/b], I have [b][c=A69800]evolved[/c][/b],
My [b][c=1F5E00]forms and features[/c][/b] all [b][c=BF6900]resolved[/c][/b].

From [b][c=005E2F]single cells[/c][/b] to [b][c=002673]complex beings[/c][/b],
My [b][c=BF0080]transformation[/c][/b] never [b][c=800000]ceasing[/c][/b].
[b][c=800055]Adaptation[/c][/b] is my greatest [b][c=BF0000]skill[/c][/b],
My [b][c=004A59]survival[/c][/b] always on the [b][c=666666]thrill[/c][/b].

Though some may view me as [b][c=003BB2]mere chance[/c][/b],
My [b][c=359E00]existence[/c][/b] is not [b][c=BF0080]happenstance[/c][/b].
For in the struggle to [b][c=BF6900]survive[/c][/b],
I am the [b][c=008099]force[/c][/b] that will always [b][c=7700B2]thrive[/c][/b].

[big][i]What am I?[/i][/big][/center]