Hierarchy of Life
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What are the levels of organization involving living things?

Your book describes levels from the biosphere down to atoms.  Keep in mind that the cell is the smallest thing that is living, and that once you try to view a cell you need magnification because they are too small to see with the naked eye.  By the time you get to molecules, even an electron microscope won't offer enough magnification to see them clearly, so at that point (and smaller) the concepts are hard to visualize.  The levels of life are shown in a figure in chapter 1.

Most students read about these levels and figure that they are easy enough to memorize and then forget later.  However, when students get lost in biology, it is usually because they cannot figure out how what they are learning fits in with anything else they have learned.  And this inability usually comes from not being able to relate from one level to another.  Please learn this scheme of the hierarchy of living things, and then USE it!

biosphere ecosystem community population individual organ systems organs tissues cells molecules
These are all bigger than one individual organism  

these three are only in multicellular organisms

  molecules can be big or small, so there are levels within this

Cells have regions within them called organelles (like a multicellular organism has organs, a cell has little organs, or organelles).  These organelles along with the cell fluid and membrane makes up the cell, but all of these components are made up of molecules.  You will learn a lot about molecules this semester so that you can understand how they make up cells.  Your book spends a lot of time describing cells and DNA, and takes the levels of life down to atoms.  We will go over that in class.

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2006 STCC Foundation Press, content by Dawn A. Tamarkin, Ph.D.

Last changed: September 05, 2007