Levels of Organization

Level 1: Cells

A basic unit of structure and function in a living thing. Complex organisms are composed of many cells in the same way a building is composed of many bricks. Cells are quite tiny, and most cannot be seen without a microscope. Cells carry on the processes that keep cells alive.

Level 2: Tissues

A group of similar cells that perform the same function. The human body contains four types of tissue: muscle, nerve, connective, and epithelial.

Level 3: Organs

A structure that is composed of different kinds of tissue. Like a tissue, an organ performs a specific job The job of an organ, however, is generally more complex than a tissue.

Level 4: Organ Systems

A group of organs that work together to perform a major function.

The different organ systems work together and depend on one another.

Keeping the Body in Balance

Homeostasis is the process by which an organim's internal environment is kept stable in site of changes in the external environment. Your body has various ways of maintaining homeostasis, which include: perspiration, eating and drinking, shivering, and responses to stress.