Q. Show the Anatomical Evidence?

Anatomy is the study of the structure, organisation and development of cells and tissues of plants and animals. For over a century taxonomists have used comparative plant anatomy as an aid in classification. The anatomical features of stems and roots are important in separating Gymnosperms from angiosperms and monocotyledons from dicotyledons. In monocot stem the vascular bundles are scattered throughout the parenchyma, whereas in dicot stem the vascular bundles are more orderly and form a definite concentric ring. In some dicots vascular cambium will form between the bundles eventually connecting throughout and forming a solid ring of conducting tissue.

Progressive series from tracheids commonly found in the gymnosperms to specialised vessel elements occur in the secondary xylem of angiosperms. All stages of specialisation from vessels wood to highly specialised vessel elements are found in contemporary flowering plants. Angiosperms with vessels wood are regarded as primitive.

The presence and structure of trichomes as well as their distribution patterns among taxa are taxonomically important. Variation pattern of trichomes also provides characters for classification. Stornatal types are of taxonomic use. Stomata of dicotyledonous plants have kidney shaped guard cells and stomata of monocotyledonous plants have dumbell shaped guard cells.

In animals the study of anatomical parts provide enough describable characters and classification based on them lead to certain conclusions as has been shown to be true for hard parts as against skin in a test case for lower taxa among mammals. A first step is to extend anatomical data beyond those traditional forms of museum specimens in mammals to the baculeum, to the ear ossicles and then to the soft parts and the second step is to push anatomical observation to deeper levels to cytology and especially karyology.