Here's why:

* Biosphere: This encompasses all life on Earth and the environments they occupy. It includes the atmosphere, the hydrosphere (oceans, lakes, rivers), and the lithosphere (Earth's crust).

* Ecosystem: A collection of living organisms and their physical environment, interacting as a functional unit. Examples include a forest, a coral reef, or a desert.

* Community: All the different populations of species that live together in a particular area.

* Population: A group of individuals of the same species living in the same area.

* Organism: A complete living being, made up of multiple organ systems.

* Organ System: A group of organs that work together to perform a specific function.

* Organ: A structure made up of different tissues that work together to perform a specific function.

* Tissue: A group of similar cells that work together to perform a specific function.

* Cell: The basic unit of life.

* Molecule: Two or more atoms bonded together.

* Atom: The smallest unit of an element that retains the chemical properties of that element.

The biosphere is the most encompassing level, encompassing all other levels within it.