Homologous structures are anatomical signs of
evolution that derived from a similar lineage. It displays a similar base
structure, but have completely different functions. Mammals are their extinct
relatives contain an indentation in the skull behind each eye socket called the
synapsid opening. Living mammals have inherited the same opening, except it’s
larger. As larger openings evolved, jaw muscles and chewing motions came to be.

There is a muscle for chewing that extends from the lower jaw to up to the
opening evolved. This might have led to better chewing and digestion. Also,
three middle ear bones were an advanced feature. The two additional ear bones
helped form a joint between the upper and lower jaws. As time progressed, the
ear bones decreased in size and moved towards the lower jaws, forming a new
joint. “Other advanced features of mammals include having hair and producing
milk for their young. Unfortunately, features like these leave no trace in most
fossils. (American
Museum of Natural History, n.d.).”

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Analogous structures are the exact opposite of
Homologous Structures, analogous structures are convergent features of different
species that are alike in function but not in structure. These species did not
evolve from a common ancestor, they just evolved in response to a similar
environment. The significance of analogous structures to the theory of
evolution is that explained by the concept of evolution. Analogous organs have
developed in the evolutionary process through adaptation of quite different
organisms to similar.