External Features of Animals

Syllabus tag: KCSE | Biology | Form 3 | Topic 1 Classification II

Lesson objectives

By the end of this topic, you should be able to:

• Describe body symmetry and segmentation in animals.
• State the external features used to identify the major invertebrate phyla.
• Distinguish the classes of Arthropoda and Chordata by external features.
• Use external features to identify and group animal specimens.

Summary

Animals are identified from body symmetry, segmentation, body covering, and appendages. Symmetry is the first division: radial in Hydra and jellyfish, bilateral in almost all others. Within Arthropoda, counting legs and body parts settles the class, and within Chordata the body covering does.