Scientists classify animals based on their body structure, level of organization, body symmetry, and presence of a backbone. The classification helps in studying and understanding relationships between species.

Key Points

• Two broad groups: Vertebrates (with backbone), Invertebrates (without backbone).
• Further divided into phyla like Arthropoda, Mollusca, Annelida, Chordata, etc.
• Basis of classification: Symmetry, coelom, body layers, segmentation.