Final answer:
The simplest level of organization in life is the atom. It is the foundational unit in the biological hierarchy, which builds up from atoms to molecules, organelles, cells, tissues, organs, organ systems, organisms, populations, communities, ecosystems, and ultimately to the biosphere.
Step-by-step explanation:
The simplest level of organization in life is the atom, which is the smallest and most fundamental unit of matter that retains the properties of an element.
In the biological hierarchy of organization, atoms combine to form molecules. Molecules, in turn, combine to form organelles that perform specialized functions within cells. Cells are the basic units of life and the smallest independently functioning biological units of an organism. Multiple cells form tissues, and these tissues organize into organs. An organ consists of different tissue types and performs a specific function within an organism. Organ systems are groups of organs working collaboratively to perform complex functions. Organisms are individual living entities capable of performing all necessary physiologic functions independently. When organisms of the same species inhabit a specific area, they form a population. Multiple populations of different species living and interacting in a common region constitute a community. The community and its physical environment operate as an ecosystem. The broadest level of organization is the biosphere, which encompasses all ecosystems on Earth.