Levels of Organization

Vocabulary terms covering cellular biology and the hierarchy of biological organization from cells to the total organism.

Cells

The smallest living entities, which all come from pre-existing cells and compose all organisms.

Tissues

Composed of similar cells that perform a common function or functions.

The $4$ types of tissues

Epithelial tissue, nervous tissue, muscle tissue, and connective tissue.

Epithelial tissue

The type of tissue that covers or lines.

Connective tissue

A category of tissue that includes bone, blood, adipose, and cartilage.

Organs

Composed of tissues that together perform a common function or functions, such as the stomach, pancreas, heart, skin, liver, and brain.

Brain and liver

The organs utilizing the most energy when the body is resting.

Organ-Systems

Groups of organs that together perform a common function or functions.

Pancreas

An example of an organ that functions as a member of more than one organ-system.

Organ-system categories

Includes nervous, muscular, integumentary, digestive, respiratory, reproductive, lymphatic, circulatory, endocrine, and urinary systems.

Organism

The level of organization that represents a complete living individual composed of organ-systems.