In the Macroevolution SparkNote we will look at the patterns that shape the evolution of all life on earth. In this SparkNote on the patterns of evolution, we will focus on patterns that affect a smaller unit of evolution, the species. Understanding these patterns on a small scale can help in determining the relatedness of species over longer periods of time.
There are three main patterns of species evolution. Convergent evolution occurs when dissimilar species gradually become more similar. This usually happens as a result of sharing similar lifestyles. Divergent evolution occurs when closely related species gradually become very different. This most familiar form of evolution occurs when species compete with each other for resources. Some species evolve without converging on similar traits or diverging to different traits. These species undergo change, but they maintain a constant level of similarity to each other. This process is known as parallel evolution.
In addition to these patterns of evolution, some species evolve in relation to each other in other ways. Species that live in a close relationship with each other, such as a predator-prey or symbiotic relationship, often evolve adaptations to each other in a process called coevolution. In predator-prey or parasitic relationships, this evolution can escalate into rapid changes in offense and defense, known as a coevolutionary arms race.