Different cells perform various functions. Notes E 1.3 Different cells perform various functions.

Organisms can be classified by their cell types. Most organisms are unicellular 3 domains of organisms: Archaea: prokaryotes, live in extreme environments Bacteria: prokaryotes, share some similarities with Archaea, but live in most environments Eukarya: Eukaryotes, include multicellular organisms (plants, animals, fungi, and some protists)

Domains Domains, kingdoms, and other classifications remain in flux and debated within the scientific community. Some scientists recognize 5 kindoms instead of 6. Some refer to domains rather than ingdoms.

Cells in multicellular organisms specialize. All mc organisms begin as a single fertilized egg cell. As cells divide, they specialize to perform specific jobs. The more specialization there is, the more complex the organism is.

A multicellular organism is a community of cells. Organisms have different levels of organization : Similar cells group together to form tissues. Tissues act together to form organs. Organs and tissues act together to form organ systems.

Scientists use models to study cells. Scientists use models to make complicated structures or processes easier to understand. Some examples of models: Mathematical or chemical equations Diagrams Process models Physical models