Handbook of Essential Biodiversity Notes is designed as a foundational guide to the study of biodiversity, offering a streamlined and comprehensive overview of key concepts. It begins with an introduction to the basic definitions and scope of biodiversity, covering its three major levels genetic, species, and ecosystem diversity. The book explores the evolutionary processes that drive the diversity of life, including speciation and adaptation, as well as the critical role biodiversity plays in maintaining ecosystem services and resilience. Readers will find sections dedicated to the major threats to biodiversity, such as habitat loss, climate change, invasive species, and overexploitation. The handbook also highlights the urgent need for conservation, with an overview of modern strategies for biodiversity preservation, including protected areas, restoration ecology, and sustainable practices. Throughout the text, real-world examples and case studies illustrate how biodiversity supports the functioning of ecosystems and human livelihoods.This handbook is an ideal reference for students, educators, researchers, and conservation practitioners, providing clear, concise notes also.