  Essentially everything of astronomical interest is either part of a galaxy,
or from a galaxy, or otherwise relevant to the origin or evolution of galaxies.
Diverse examples are that the isotropic composition of meteorites provides
clues to the history of star formation billions of years ago, and cosmological
tests for the deceleration of the Universe are strongly affected by changes in
the luminosities of galaxies during the lookback time sampled. The aim of this
article is to review some of the vital connections that galaxy evolution makes
among many astronomical phenomena.
