bio hierarchy

Atom

The basic unit of matter; building blocks of everything

Molecule

Two or more atoms joined together (e.g., water, DNA)

Organelle

A tiny structure inside a cell that has a specific job (e.g., mitochondria, nucleus)

Cell

The basic unit of life; can be single-celled or part of a multicellular organism

Tissue

A group of similar cells that work together to do a job (e.g., muscle tissue)

Organ

A structure made of different tissues that performs a specific function (e.g., heart, lungs)

Organ System

A group of organs that work together to carry out a major function (e.g., digestive system)

Organism

A living individual

Population

A group of organisms of the same species living in one area

Ecosystem

All living things plus non-living things in an area interacting together

Biome

A large area with similar climate, plants, and animals