Cells Are Us : Levels of Organization

Introduction

Why It Matters?

Introduction

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 the 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.

Objectives:

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.

Why It Matters?

Did we explain well enough what “levels of organization” mean? Think about your school, as an example. Its levels of organization can include:

Buildings (classrooms, library, offices, gym, lunchroom, etc.)
Administration (school board, superintendent, principal)
Activities (teaching, learning, sports, club meetings, etc.)

The Living and the Dead

Ever wonder what makes the difference between being dead and alive? To be alive you have to be well organized – or at least your cells do. Consider the pictures of water or the rocks … dead, right? Water only has one kind of molecule in it, and these molecules are randomly moving around – not very well organized. Rocks may have several kinds of molecules that are locked into position by simple interactions with each other. However, these molecules don’t really DO anything.

Survival

Non-living things don’t have to do anything.
Cells have to DO many functions in order to stay alive.
To DO so can require correct operations at many levels of organization.

The normal function of cells depends on normal function of the many structures inside cells that help cells survive. These structures are called “organelles” (“little organs”). When our cells are healthy, we are healthy. When our cells are sick, we are sick. Sick cells reflect disease.