Question

Evidence from anatomy of organic evolution

Answer 1

2. Evidences from Comparative Anatomy and Morphology:

There are similarities and differences among organisms of today and those existed years ago. These evidences are as follows.

(i) Organ Systems:

The different systems of animal body are similar in many groups of organisms, e.g., nervous sys­tem, blood vascular system, respiratory system, excretory system, etc. Respiratory system of terrestrial vertebrates has two lungs, a trachea, a larynx, nasal chambers and nostrils. Likewise, the blood vascular system of all vertebrates contains a heart, ar­teries, veins and lymph vessels.

(ii) Homologous organs:

Richard Owen (1804-1892) introduced the term homolo­gous. The organs which have the same fundamental structure but are different in functions are called homologous organs. These organs follow the same basic plan of organisation during their development. But in the adult condition, these organs are modified to perform different functions as an adaptation to different environments. The homologous structures are a result of divergent evolution. Homology indicates common ancestry.

(iii) Analogous Organs:

The organs which have similar functions but are different in their structural details and origin are called analogous organs. The analogous structures are the result of convergent evolution.
(iv) Vestigial Organs:

The organs which are present in reduced form and do not perform any function in the body but correspond to the fully developed functional organs of related animals are called vestigial organs. They are be­lieved to be remnants of organs which were complete and functional in their ancestors.