The variability among living organisms from all sources including terrestrial, marine and other ecosystems and the ecological complexes of which they are part which includes diversity within species, between species of ecosystems refers to

The definition provided in the question is the formal definition of 'biological diversity' (often abbreviated as biodiversity). According to Article 2 of the Convention on Biological Diversity (CBD), biological diversity refers to the variability among living organisms from all sources, including terrestrial, marine, and other aquatic ecosystems, as well as the ecological complexes of which they are part. This concept encompasses three distinct levels: genetic diversity (within species), species diversity (between species), and ecosystem diversity [1]. While ecological diversity is a component of this broader term, it specifically refers to the variety of habitats and ecological processes [3]. Biological diversity is the comprehensive term that captures the total variety of life on Earth, resulting from millions of years of evolutionary history [2]. It represents the variability within and among all living entities rather than just the sum of biological resources.

Sources

1. [1] FUNDAMENTALS OF PHYSICAL GEOGRAPHY, Geography Class XI (NCERT 2025 ed.) > Chapter 14: Biodiversity and Conservation > BIODIVERSITY AND CONSERVATION > p. 115
2. [3] FUNDAMENTALS OF PHYSICAL GEOGRAPHY, Geography Class XI (NCERT 2025 ed.) > Chapter 14: Biodiversity and Conservation > Ecosystem Diversity > p. 116
3. [2] Environment and Ecology, Majid Hussain (Access publishing 3rd ed.) > Chapter 12: Major Crops and Cropping Patterns in India > Glossary > p. 102