English: The simplest unit of life is the atom, like oxygen. Two or more atoms make up a molecule, like carbon dioxide. An assembly of many molecules makes up a macromolecule, such as an assembly of phospholipids makes a vesicle. Multiple macromolecules form a cell, like a Clara cell. A group of cells functioning together is a tissue, for example, Epithelial tissue. Different tissues make up an organ, like a lung. Organs work together to form an organ system, such as the Respiratory System. All of the organ systems make a living organism, like a lion. A group of the same organism living together in an area is a population, such as a pride of lions. Two or more populations interacting with each other form a community, for example, lion and zebra populations interacting with each other. Communities interacting not only with each other but also with the physical environment encompass an ecosystem, such as the Savanna ecosystem. All of the ecosystems make up the biosphere, the area of life on Earth.

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