"The Tangled Bank" is a metaphor used to describe the complex and interconnected web of life in ecosystems. It illustrates how various species, including plants, animals, and microorganisms, interact with one another and their environment. This concept emphasizes biodiversity and the importance of each organism in maintaining ecological balance. The term was popularized by Charles Darwin in his work on evolution, where he compared the diversity of life to a bank filled with different resources. Each species contributes to the overall health of the ecosystem, much like how different investments can strengthen a financial portfolio.