Question

Discuss the natural system of organisms

Answer 1

Explanation:

It is a system of classification which takes into consideration comparable study of a number of characters so as to bring out natural similarities and dissimilarities and hence natural relationships among the organisms.

The system employs those characters which are relatively constant. They include morphological characters, anatomical characters, cytological characters, physiology, ontogeny or development, reproduction, cytochemistry and bio­chemistry, experimental taxonomy, etc.

The characteristics are helpful in bringing out maxi­mum number of similarities in a group and comparable differences with other groups of organisms. For example, mammals are characterised by the presence of mammae, hair, vivipary, 4-chambered heart, de-nucleated erythrocytes and warm blooded nature.

Birds possess wings, feathers, pneumatic bones, ovipary, 4-chambered heart, nucleated erythro­cytes and warm-blooded nature. Similarly, fishes do not possess limbs but fins. Their body is covered with scales. Respiration is through gills. Heart is two-chambered. They are cold­blooded.

In natural system of classification of Organisms, homology is brought out through the study of internal and external characters. Homology is the relationship of comparable structures having been derived from a common form. For example, the fore arm of different land vertebrates has the same pentadactyl constitution.

It is externally much different in different organisms to perform different functions like grasping in human beings, running in horse, swimming in whale, flight in bird or a bat. Homology shows how each organ or structure has evolved in different groups to suit different functions. Homology is studied in case of bio-chemicals as well.

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