In celebration of the day, one of my favourite (and the final) passages in Origin:

It is interesting to contemplate a tangled bank, clothed with many
plants of many kinds, with birds singing on the bushes, with various
insects flitting about, and with worms crawling through the damp earth,
and to reflect that these elaborately constructed forms, so different
from each other, and dependent upon each other in so complex a manner,
have all been produced by laws acting around us. These laws, taken in
the largest sense, being Growth with Reproduction; Inheritance which is
almost implied by reproduction; Variability from the indirect and
direct action of the conditions of life, and from use and disuse: a
Ratio of Increase so high as to lead to a Struggle for Life, and as a
consequence to Natural Selection, entailing Divergence of Character and
the Extinction of less-improved forms. Thus, from the war of nature,
from famine and death, the most exalted object which we are capable of
conceiving, namely, the production of the higher animals, directly
follows. There is grandeur in this view of life, with its several
powers, having been originally breathed by the Creator into a few forms
or into one; and that, whilst this planet has gone cycling on according
to the fixed law of gravity, from so simple a beginning endless forms
most beautiful and most wonderful have been, and are being evolved.