"This video in the Core Biology series provides an excellent introduction to ecology from a historical perspective, highlighting the pioneers who established environmental science as a science in its own right. The program begins with a description of the characteristics of biomes and leads the viewer to an understanding of the concept of ecology and the interaction between plants and animals in an ecosystem. Providing many examples of these interactions and using diagrams of food webs and food chains, the narrator deals with energy input and how ecosystems run in opposition to the second law of thermodynamics. The concept of population ecology is introduced, and the terms "niche" and "habitat" are defined with clear examples. and the video shows how these concepts are interrelated. The laws that govern the interaction between populations in a particular habitat are also discussed. The program ends with a discussion of the Gaia hypothesis, which is used to explain the interactions between the biotic and abiotic components of ecosystems, the self-regulatory mechanisms of the planet that maintain its huge biodiversity, and the impact of human beings on that biodiversity."