Are oval-shaped galaxies younger or older, larger or smaller than other galaxy shapes

Answer

There is no simple, one-dimensional evolution sequence that fits all galaxies.

One distinguishes (several kinds of) spiral galaxies, elliptical galaxies, lenticular galaxies (a transition between the two previous ones) and irregular galaxies. Spiral galaxies are all fairly large, because if there is little mass, the spiral structure cannot develop. Ellipticals can be small or very large. The largest galaxies (in terms of mass) are always ellipticals.

Where a reasonably clear evolutionary relationship can be shown is between spirals and the largest ellipticals. The latter are believed to have arisen from the collisions of several spiral galaxies. In such collisions, the stars don’t actually collide, but the interstellar clouds do. So much so that all those clouds are turned into stars. The result is a large mass of stars, an elliptical galaxy. That could engulf other spiral galaxies. Indeed, the largest ellipticals systematically occur at the center of large galaxy clusters.

On the other hand, it is now becoming increasingly clear that spiral galaxies did not arise all at once, but gradually, through the accumulation of smaller galaxies. And that in turn may have been elliptical or rather irregular galaxies.

Do galaxies change shape? Yes. What determines the evolution of galaxies is on the one hand internal – the way in which the gas and dust are converted into stars – and on the other external – collisions with other galaxies.