WHATS IS A CELL? ---------------------- Where Life Happens A cell is the smallest unit of life that can carry out all the functions of a living thing. The size shape, and structures are very diverse. Living things may either be unicellular (consisting of one cell) or multicellular (many-celled). Bacteria are one of the type of unicellular organism. Most of the organisms you are familier with- including yourself- are multicellular. Cells can also vary greatly in size. Notice that the smallest cell is a bacterium. About 8000 of the smallest bacteria could fit inside one of you red blood cells. The longest cells are the very thin nerve cells in small animals. These cells can be more than a meter long. The cell with the greatest volume is an unfertilized ostich egg. It has a liters full of contents, including stored food. Noctice also that the shape of cells can vary greatly. A cell's shape is related to its function. A long nerve cell for example, can cary messages from your brain to your toes. Long slender muscel cells thats are grooped together form a long slender muscle tissues. The contraction and relaxation of mucle tissues is responsible for the movment in animals. DISCOVERY OF CELLS ---------------------- A Small New World You are living at a time when a great deal is known about microscopic life. However, in the beggining of the 1600s people knew only about organisms they could see with the unaided eye. They certanly had no knowlege of the existance of cells. The invention of the microscope was one of the most important break throughs in biology. The microscope was invented by a trio of Dutch eyeglass makers in the late 1500s. It consited of a tube with lenses ground from rock crystal, and it magnified objects up to nine times their actual size. Many other inventors produced variations of this simple model in the early 1600s. In 1965 the British scientist Robert Hooke published a set of drwings illustrating what he had observed with a microscope. One of theses drawings Hookes described he saw empty chambers, he saw "cells" because they reminded him of the small rooms, or cells, in a monistary. Scientists later leardnd that the cells Hooke observed had once contained living matter. In the early 1670s Anton van Leeuwenhoke (LAY-vun-hohk)a Dutch fabric store owner, began to grind lenses as a hobby. Leeuwenhoke used his handheld microscopes to examine materials such as pond water and blood. To his amazment, he dicovered a world of microscopic organisms and living cells. CELL THERORY ---------------- BIOLOGISTS BUILD A THEORY
