11th Biology Chapter 4

1. Basis of Classification

Classification is based on common fundamental features such as arrangement of cells, body symmetry, and patterns of digestive, circulatory, or reproductive systems among animals.

2. Levels of Organisation

Animals exhibit different levels of organization from cellular to systems level. Basic functionality and complexity in structures vary accordingly across different phyla.

3. Symmetry

Animal symmetry can be categorized as asymmetrical, radial, or bilateral based on the species, affecting their overall form and arrangement of body structures.

4. Diploblastic and Triploblastic Organisation

Animals are categorized based on the number of embryonic layers: diploblastic animals have two layers, and triploblastic animals have three, which affects their developmental complexity and organ systems.

5. Segmentation

Metameric segmentation refers to the division of the body into segments, which can be seen in animals like earthworms, allowing for more sophisticated organ differentiation and function.

6. Notochord

Presence or absence of a notochord, a rod-like structure seen during embryonic development, distinguishes chordates from non-chordates.

7. Classification of Animals

Detailed descriptions of phyla based on characteristics such as body structure, complexity, developmental patterns, and reproductive strategies help in understanding the extensive diversity found in the animal kingdom .