What happens after extinction?

The situation after an extinction is considered. An importan! post-extinction event is diversification and three main aspects concerning this must be taken into account: a) ecological aspects; b) natural selection, adaptation and morphogenesis, and e) macroevolutionary aspects. Adaptive radiations come usually after a mass extinc tion. The first point deals with ecology; morphological novelties and a suitable interna! structure of ecosys tems are as importan! as good physical environments for diversification. A second point considered is how natural selection works in the case of dealing with constrained or unconstrained developmental systems. The third point considers the action of non adaptive macroevolutionary processes at the beginning of diversifica tion and later, strong natural selection if ecological niches are gradually filled. Chance as a macroevolutionary factor is also considered. en desarrollo sometidos, o no, a constricciones. El tercer punto considera la acción de procesos macroevolutivos no necesariamente adaptativos al comienzo de la diversificación (y divergencia), seguidos de fuerte·acción de la selección natural si los nichos se van llenando gradualmente. También se ha considerado el azar como factor macroevolutivo. Palabras