When you look at a pyramid, you'll notice that its broad base gradually narrows as it extends upward. The same holds true for the organization of life on Earth.
At the base of this hierarchical structure, is the most inclusive level of organization, such as an ecosystem. As you climb the pyramid, the levels become less encompassing and more specific. Let's take a look at this magnificent pyramid, starting with the ecosystem at the base and culminating with the atom at the peak.
Our tour begins with the ecosystem. Ecosystems involve interactions between communities and their environment. Communities consist of different populations (groups of organisms of the same species) in a given geographic area. The environment includes everything from people to plants.
The next stop is the organism. Yes, that's right, that means you! Living organisms are highly ordered and have the ability to grow, develop, and reproduce. Complex organisms, including humans, rely on the cooperation between organs, tissues, cells, and molecules to exist.
Moving right along, we come to our next level--organ systems. Some examples are the circulatory, digestive, nervous, skeletal, and reproductive systems which work together to keep the body functioning normally. For instance, nutrients obtained by the digestive system are distributed throughout the body by the circulatory system. Likewise, the circulatory system distributes oxygen that is taken in by the respiratory system.
Climbing higher still, we arrive at the organs: i.e., the heart, liver, brain, skin, and stomach. Organs are composed of different types of tissue arranged together to perform specific tasks. For example, the brain is composed of several different types including nervous and connective tissues.
Next, we have tissues. No, not the kind you use to blow your nose! Simply put, tissues are groups of cells with both a shared structure and function. Animal tissue can be grouped into four subunits: epithelial tissue, connective tissue, muscle tissue, and nervous tissue.
As we approach the top of our pyramid, we arrive at the next level-- cells. Cells are the simplest form of living units. Cells contain structures called organelles which are responsible for everything from housing the cell's DNA, to producing energy. Processes that occur within the body are carried out on a cellular level. For example, when you move your leg, it is the responsibility of nerve cells to transmit these signals from your brain to the muscle cells in your leg.
Molecules reign supreme on the next level. Molecules are composed of atoms and can be arranged into large molecular structures such as chromosomes, proteins, and membranes. Some of these proteins may be grouped together to become the organelles that make up your cells.
Our tour ends with the ever so tiny atom. It takes extremely powerful microscopes to view these units of matter (anything that has mass and takes up space). Elements such as carbon, oxygen, and hydrogen are composed of atoms.
So there you have it. The pyramid of life is a hierarchical structure for the organization of life. To summarize, the organization for complex organisms goes as follows: ecosystems, organisms, organs systems, organs, tissues, cells, molecules, and atoms.