A pentadactyl forelimb in vertebrates, meaning a forelimb with five digits, serves a variety of functions depending on the animal's environment, showcasing how a single basic structure can be adapted through evolution to suit different needs, like swimming, flying, running, or grasping, all while maintaining the underlying five-digit pattern as a result of shared ancestry.
Physiological evidence is an evidence of evolution that deals with the functions of body parts among different species. For example, analogous structures are body parts of different species that have a similar function but can look different.
Moreover, physiological evidence focuses on the specific functional mechanisms and processes that underline the pentadactyl limb's operation while comparative anatomy addresses the evolutionary and anatomical origins of the pentadactyl plan. In other words, Anatomy is the study of the body's physical structure, while physiology is the study of how the body functions.
While both comparative anatomy and physiological evidence can support the concept of the pentadactyl forelimb in vertebrates, the key difference lies in the focus of study: comparative anatomy examines the structural similarities in bone arrangement across different species, whereas physiological evidence investigates how the limb functions and adapts to different behaviours in each species; essentially, comparative anatomy looks at the "blueprint" of the limb, while physiology examines how that structure is used in different contexts.
Embryological evidence of the pentadactyl forelimb of vertebrates includes the regulation of gene expression during limb development.
The fossil record of pentadactyl forelimbs shows that many vertebrates have a similar bone structure, even though their limbs look different on the outside.