Biodiversity

Biodiversity refers to the variety and variability of life on Earth, encompassing all organisms, their genetic differences, and the ecological complexes (communities and ecosystems) they form.

The term was coined by Walter G. Rosen (1985) and later popularised by the sociobiologist Edward O. Wilson. Some sources attribute broader popular usage of the concept to Wilson's writings in the late 1980s; this historical nuance is occasionally tested in exams as an assertion-reason item.

Biodiversity is studied at three hierarchical levels:

• Species diversity generally declines from the tropics toward the poles (the latitudinal gradient).
• Tropical regions such as the Amazon and the Western Ghats host disproportionately high numbers of species relative to their area.

• Present-day biodiversity is the result of over 3.5 billion years of evolution.
• Current rates of species loss, driven largely by human activity, are estimated to be far higher than natural background extinction rates.
• This makes biodiversity conservation a critical global priority, forming the basis for the next topic in this chapter (threats to biodiversity and conservation strategies).

• Biodiversity has three levels: genetic, species, and ecosystem diversity.
• The term was coined by Walter Rosen and popularised by E.O. Wilson.
• Biodiversity provides essential ecosystem services: nutrient cycling, pollination, climate regulation, and more.
• Species diversity decreases from the tropics to the poles.
• Biodiversity ≠ species count alone; genetic and ecosystem variation matter equally.
• Present biodiversity reflects billions of years of evolution and is under threat from human activity.