04.1 BIO Levels of Organization

Atom

Smallest unit of matter that retains the properties of an element

Molecules

Groups of two or more atoms held together by chemical bonds

Macromolecules

Four main classes of large biological molecules (carbohydrates, lipids, proteins, nucleic acids)

Cell

Basic unit of life

Tissue

A group of similar cells that perform the same function.

Organ

A collection of tissues that carry out a specialized function of the body

Organ system

Group of organs that work together to perform a specific function

Organism

A living thing

Population

A group of individuals of the same species that live in the same area.

Community

A group of interdependent organisms inhabiting the same region and interacting with each other

Ecosystem

A biological community of interacting organisms and their physical environment.

Biome

A group of ecosystems with similar climates and organisms

Biosphere

Earth

Organelle

A tiny cell structures made of macromolecules that carries out a specific function within the cell