Biology
Biology is the natural science that involves the study of life and living organisms, including their physical structure, chemical composition, function, development and evolution. Modern biology is a vast field, composed of many branches. Despite the broad scope and the complexity of the science, there are certain unifying concepts that consolidate it into a single, coherent field. Biology recognizes the cell as the basic unit of life, genes as the basic unit of heredity, and evolution as the engine that propels the creation of new species. Living organisms are open systems that survive by transforming energy and decreasing their local entropy to maintain a stable and vital condition defined as homeostasis. See glossary of biology.
Ecosystem
An ecosystem is a community made up of living organisms and nonliving components such as air, water, and mineral soil. Ecosystems may be studied either as contingent collections of plants and animals, or as structured systems and communities that are governed by general rules. The biotic and abiotic components interact through nutrient cycles and energy flows. Ecosystems include a network of interactions among organisms, and between organisms and their environment. Ecosystems can be of any size but one ecosystem has a specific, limited space. Some scientists view the entire planet as one ecosystem.