1.2

Atom

The smallest and most fundamental unit of matter.

Molecule

A chemical structure consisting of at least two atoms held together by one or more chemical bonds.

Macromolecules

Large molecules typically formed by polymerization, such as DNA.

Organelles

Small structures within cells that contain aggregates of macromolecules surrounded by membranes, e.g., mitochondria and chloroplasts.

Cells

The smallest fundamental unit of structure and function in living organisms.

Prokaryotes

Single-celled organisms that do not have membrane-bound nuclei.

Eukaryotes

Multi-cellular organisms with membrane-bound organelles and a membrane-bound nucleus.

Bacteria and Archaea

Domains that classify single-celled organisms as prokaryotes.

Animal cells, plant cells, fungi, and protists

Types of eukaryotic cells.

Evolution

The source of diversity among living organisms.

Phylogenetic tree

A diagram that depicts the lines of evolutionary descent of different species, organisms, or genes from a common ancestor.