The ecosystem is the fundamental building block of ecology. It is a geographical area wherein living organisms, including microbes, plants, animals, and various abiotic factors, interact with each other and form a sphere of life. These ecological interactions, encompassing competition, predation, symbiosis, and herbivory, play a significant role in maintaining homeostasis in an ecosystem. Multiple ecosystems with similar environmental conditions, including rainfall patterns, temperature, and soil type, combine to form a biome. This acts as the cornerstone of ecology, a branch of science that studies the interactions between an organism and its environment and among themselves. Consequently, to completely comprehend ecology, it becomes vital to gain knowledge about ecosystems, biomes, and ecological interactions occurring in them, which further aids in biodiversity conservation. In this premise, this chapter discusses various diverse ecosystems, key attributes of different biomes, and the intricate network of ecological interactions that exist between organisms and their environments. Furthermore, the impact of anthropogenic interference and the significance of ecosystem conservation are also highlighted.