Ecology is the study of ecosystems, which consist of biological communities interacting with their physical environments. An ecosystem includes all the living things in a given area, like plants and animals, along with non-living factors, connected through nutrient cycles and energy flows. Ecosystems provide services like food, water filtration, climate regulation, and cultural benefits. Ecosystems can be small, like a pond, or large, like a forest. They are classified as natural or artificial/human-made and include biomes defined by factors such as plant life and climate. Biomes include terrestrial, freshwater, and marine environments.