This textbook has been designed to meet the needs of B.Sc. Fifth Semester students of Zoology as per Common Minimum Syllabus prescribed for all Uttar Pradesh State Universities and Colleges under the recommended National Education Policy 2020. It comprehensively covers Paper 1, namely, Diversity of Non-Chordates, Parasitology and Economic Zoology. Theory part of this book aptly discusses the comprehensive identification abilities of non-chordate diversity and also explains the structural and functional diversity of non-chordates. Experiments corresponding to the theoretical topics and examples have been presented systematically to help students achieve sound conceptual understanding and learn experimental procedures.