Cells Are Us - Levels of Organization (Introduction)

To the Teacher:

In teaching Cells are Us, it is useful, but not essential, to do this lesson first.

Overview of Cells

A cell is the simplest living thing that can have a "life of its own."
Germs (viruses and bacteria) are smaller than cells and most can not survive alone. To survive, many germs have to invade cells and steal some of the functions of cells, often damaging cells in the process.

Levels of organization, showing relation of atoms to cells to organisms.

Each item represents a different level of organization. Organelles, for example, operate only within a cell and what they do has direct effects only on the cell. A tissue, such as muscle for example, operates on a higher level of organization, because it has many cells that work together to perform that tissue's function in the body. Two or more tissue types occur in organs, which represent yet a higher level of organization.

After completing this lesson, you should find it easy to:

Understand the levels of organization of living systems in terms of structures and functions.
Identify the major characteristics that most cells have in common.
Identify the parts of a cell and its organelles, and understand the general function and importance of each part of the cell.

After completing "Cells Are Us," you can visit the module on "Organ Systems," which shows how the level of organization increases as cells group together to perform special functions (such as brain cells, liver cells, muscle cells, and so on). In our curriculum there are also units dealing with ecosystems, where many animals and plants live together and interact in many ways.