Biodiversity - "the variety of organisims found within a specified geographic region"... American Heritage College Dictionary.
Ecology - "the science of the relationships between organisms and their environment or the relationship between organisms and their environment"... American Heritage College Dictionary.
Biodiversity Our Living World: Your Life Depends On It! - PSU 2001 Ke Chung Kim
Explains biodiversity as our natural interconnected web of variations of plants, animals, fungi and microorganisms, our life support system on Earth.
PA Natural Heritage Program website.