Evolution occurs in patterns, and it can have direction.
Convergent evolution is the evolution toward similar traits in unrelated species. Divergent evolution describes evolution toward different traits in closely related species. The video below, Convergent and Divergent Evolution, goes into these two types of evolution.
Coevolution is the process of two or more species evolving together over time. Take the time to watch the Brightstorm video, Coevolution. Coevolution can occur in both beneficial and competitive relationships.
Finally, species can become extinct. There are two types of extinctions to know about. Background extinctions occur continuously at a very low rate. Background extinctions occur at about the same rate as speciation, and usually affect only a few species in a small area. They are also caused by local changes in the environment. Mass extinctions are rare, but are much more intense. A mass extinction would destroy many species at a global level, and would be caused by a catastrophic event.