The existence of life forms called cells is not a new concept to mankind, though man may have been undermining its importance. Cells are the basic units of our existence as organisms. They are tiny units that serve as blocks with which our whole system is built. Cells also carry basic information about the organism in the DNA. Plants, terestial and aquatic animals all have different forms and natures, but they all are made of cells. These cells have similar contents, these contents are necessary for the functioning of the cell and the whole organism in turn. The cells may have different shapes and structures or may have their contents in different ratios, depending on the function the cell is supposed to serve. This will help us understand how living things, including human beings, function.
While we cannot see cells using the naked eye, they are the building blocks of living structures we see. An aggregation of similar cells results in the formation of tissues. Consequently, the tissues combine to form body organs such as the heart and lungs. Body organs coordinate their functions and work as organ systems such as the digestive system. A human being, therefore, results from the combination of organ systems. As earlier described, it serves as the building block for living organisms. There are many types of cells in a living organism, with some serving very specialized roles. Red blood cells, for example, carry oxygen in the blood. Nerve cells, which are found in the brain, are responsible for transmitting impulses which are control communication between parts of the body. In plants, xylem cells transport water and mineral salts from the roots to the leaves. This illustrates the diversity of cells in complex organisms. An organism cannot survive without the function of specialized cells. Some cells produce substances that are necessary for the organism as a whole. An example is pancreatic cells in human beings which are responsible for the production of insulin. The product, in this case, controls blood sugar. I am sure you have all seen a diabetic person give themselves an insulin shot. Cells usually divide forming two copies from one. This serves a variety of purposes in living things: reproduction, growth and development, and repair. The processes that we see in living organisms stem from the cell. This is a perfect illustration of its importance as a guarding of life.