Question

Explain why anatomical and molecular features often fit a similar nested pattern. In addition, describe a process that can cause this not to be the case.

Short answer

The main reason for the nested pattern is that all the living organisms share a common ancestor. This pattern is also called homology, where certain organisms are anatomically similar and share molecular similarities. Hence, the nested pattern appears due to the homologous evolution.

Convergent evolution is the process that can prevent nested patterns of evolution.

Step-by-step solution

Evolutionary similarities

The living organisms possess varying degrees of similarities. Different organisms often arise from a single ancestor but evolve according to their respective habitats. Therefore, several species appearing in different environments might possess similar anatomical arrangements.

The reason for the nested pattern

The evolutionary pattern is supposed to occur in a nested manner. Scientists believe that organisms occur in a nested hierarchical manner instead of nested boxes. Hence, one can infer that the living organisms occur in a nested manner as they share certain anatomical and molecular similarities.

This phenomenon is called divergent evolution.

Process which opposes nested pattern 

The nested pattern of evolution occurs due to divergent evolution. In contrast, anatomical similarities can also arise due to convergent evolution, where unrelated organisms seem very similar. The convergent evolution can result in the opposite of nested patterns.