Re: What living things don't have cells?

Adam:
     I think that is an interesting question.  You obviously know that 
most life, such as trees, fish and people are made up of lots of 
individual cells, but what else is out there that doesn't have any cells, 
or if I read your question another way, is there anything out there that 
doesn't have cell(s), that is more than one.  So, that being said, I will 
tell you about some of the things that have only one cell, and then 
something about some stuff that may or may not be alive, but certainly 
doesn't have a cell at all...
    There are basically two kinds of cells on Earth and scientists use 
these two kinds of cells as a way of dividing up creatures.  One kind, is 
called eukaryotes, and the most defining feature of these cells is that 
they have a nucleus and lots of organelles that handle all sorts of 
functions from making energy to transporting stuff around the cell.  Most 
life is this kind, from people to plants.  Of this kind of cell, there are 
several types of life that only have one cell... Some algae, most of the 
fungi, like baking yeast and bread mold, and some protists like the 
amoeba.  All of these are only one cell and they are alive, and contain 
everythig they need within them to grow, eat, get rid of waste, make 
energy, and reproduce. 
     The other type of cell is called a Prokaryote.  These cells are 
usually smaller than the other kind and don't have a nucleus at all.  
These are the bacteria, and thousands of them can fit on the head of a 
pin.  And the smallest known cell in the world is a bacteria called 
Mycoplasma, and many of these could fit inside most 'regular' bacteria, so 
it is a pretty small cell.  
     There is actually a third kind of cell, called archeae, but they are 
a lot like bacteria in many ways, and are basically all one-celled 
organisms as well.  
     The only things on Earth that I know of that don't have any cell at 
all are the viruses.  There is considerable discussion on whether they are 
actually 'alive' however.  Viruses, are basically bags of protein that 
protect genetic information that when it gets into cells, takes over their 
machinery and tells it to make more viruses.  Viruses do not consume 
anything, produce energy, replicate autonomously, and with just a few 
exceptions and a couple of proteins, do not perform any meaningful 
biological chemistry by themselves.  Viruses are very common and they 
range from the common cold, A Rhinovirus, to things you got shots for as a 
child, polio, hepatitis, and a few others.  
     So, Adam, the take home message is that life as we know it requires 
cells.  And the invocation of the cell was crucial to allow life to exist 
on this planet.  The cell allows a compartment to be made so 'life' can 
keep stuff out, but more importantly keep stuff in, and how the first cell 
came to be is still a great mystery to scientists, but many people study 
that very thing.  Here is a pretty good web page that has lots of 
microscopic pictures of cells and viruses.  They are electron-microscope 
images, and look really cool too.  I also included a .jpg of a virus for 
you to see.  It is a virus that infects bacteria, called a phage.  Yes, 
bacteria can get viral infections too...  Viruses are so small that 
hundreds of them can fit inside a single bacteria, and thousands of those 
will fit on the tip of a pencil.  Good luck, and enjoy the images, I think 
they are nifty  Thanks.

-Matt-
http://www.pbrc.hawaii.edu/~kunkel/gallery/no-frame.html