Key Patterns of Evolution: From Divergence to Biological Progress
The most fundamental pattern of evolution is . This is the process where related organisms, sharing a common ancestor, evolve different traits as they adapt to different environments. A classic example is the variation in limb structure among mammals—the wing of a bat and the flipper of a whale are homologous organs that arose through divergence. Key Patterns of Evolution: From Divergence to Biological
1. Forms of Evolutionary Change: Divergence, Convergence, and Parallelism This leads to the formation of analogous organs,
Evolutionary theory, particularly the work of A.N. Severtsov, identifies three main paths to biological progress: its geographic range (area) is expanding
In contrast, occurs when unrelated species develop similar traits because they inhabit similar environments. This leads to the formation of analogous organs, such as the wings of a butterfly and a bird. A third, more complex pattern is parallelism , where related groups independently acquire similar adaptations after they have already diverged, such as the development of saber-toothed features in both placental and marsupial mammals. 2. The Directions of Evolution: Progress and Regress
Biologists define the "success" of a group through the lens of . A group is in a state of progress if its population size is increasing, its geographic range (area) is expanding, and it is diversifying into new species. Conversely, biological regess is characterized by a drop in numbers, a shrinking range, and a loss of biodiversity, which often leads to extinction. 3. Paths to Success: How Progress is Achieved