 So, I have a friend that I do a lot of outdoor activities with and I'm always interested in the kinds of questions that he asks me. These questions always start out something like, so you're a biologist, why is it that the sky is blue or why does this fish have this particular coloration or why is the water the color it is on this particular day or it may range all the way up to something like what is the doctor trying to tell me when he talks about a particular condition. I'm always curious to see what kinds of questions come from this guy and it always starts well you're a biologist so just because one's a biologist doesn't mean they know everything there is to know about life which is a good time to think about this concept of levels of organization. There are many different approaches one can take to the study of life and so what we're going to do is just list all the different ways that that we can approach the study of life and have a little discussion about each of them. So we start off with what we call the atom and certainly if you've had a chemistry class or a physical science class in high school you know know about the atom hopefully. The atom is the smallest complete unit of matter. Now it's important to understand what we mean by the smallest complete unit of matter. There are things that are smaller than atoms we have subatomic particles such as protons and neutrons and electrons and mesons and bosons but these subatomic particles by themselves do not represent any complete piece of matter so the atom is the smallest complete unit of matter. Now we mentioned the term matter which we should define. Matter can be defined as anything that takes up space or anything that has mass but something has mass it takes up space so sometimes people just say anything that has mass and takes up space. Things exist that aren't matter but those are things like emotions or thoughts but anything that that takes up space within the room or the environment is considered to be matter. One of my favorite tricks to play on students is I'll ask them to to think of something that is not matter and I'll write on a on a card because I know what they're going to say and almost always somebody in the room will write down air and they'll say air is not matter but then I remember a car that I once had and I had to crack the window a little bit to shut the door because when I tried to shut the door and tried to compress all of that air it didn't work very well and I had a hard time getting the door shut so anything that takes up space even the air in the room is is matter. There are different types of matter and the different types of matter are called elements and these elements are arranged in what we call a periodic table. Popular elements include things like gold like to have a lot of that or silver or platinum, hydrogen, helium, nitrogen, oxygen, carbon all of these are different types of matter which we call elements and of course there are different phases of matter and the different phases of matter are things like solid and liquid and gas. We'll talk about water a little bit later in different forms that water can exist in. Solid water of course we call ice gaseous water we refer to as steam and liquid water well we call it water so the atom is the first in our levels of organization. People who study atoms are called chemists. The next level of organization is the molecule level and we have a molecule when two or more atoms are chemically combined. A good example of a molecule would be a water molecule and of course a water molecule is composed of two hydrogens and an oxygen so we have two hydrogen atoms and an oxygen atom that make up a molecule of water. So here we have three atoms that are chemically combined. We could talk about larger molecules like glucose or or DNA and we'll talk about all of these later. So the next level of organization I like to include is the macromolecule level and the macromolecule level just recognizes that there are some molecules especially important to life that are very large molecules that's what macro means is large. Macromolecules include things like proteins, DNA, polymers and that's in an upcoming chapter that where we'll learn about the macromolecules important to life. The next level of organization is what we call the organelle level. Organelle literally means little organ and organelles are parts of cells that have specific functions. For example you may think of the nucleus of the cell which is the cells control center so to speak or you may have heard about the mitochondria which is often referred to as the powerhouse of the cell and there are others, Golgi apparatus, smooth endoplasmic reticulum, rough endoplasmic reticulum, etc. So we finally get to the cellular level of organization and earlier we learned that the cell is the fundamental unit of life. All living organisms are composed of cells and there are all sorts of different kinds of cells but if it's living it's made of cells. It's not until we get to this level of organization the cellular level that life actually exists. Organelles by themselves do not demonstrate the characteristics of life but when we bring all these together molecules made of atoms and macromolecules which are very large molecules that can be components of organelles and then different organelles working together we get the cellular level of organization. Now we have life, something that can demonstrate those characteristics of life that we talked about before. Now I sort of think about a box that I have in my shop and I have several fishing reels that I've taken apart and tried to put back together but I was missing a piece and I never could get them back together just exactly right and so even though I have all of these parts that could be used to make a fishing reel because they're not put together right or because one is missing the fishing reel doesn't work. So when we get to the cellular level we finally have life all the right parts in the right places.