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Levels of Organization Mrs. McCabe 04/08 Adapted from Joe Krupens, Standley Middle School Division of Labor & The First Level Within multi-cellular organisms there is division of labor. Division of labor means that the work (labor) of keeping the organism alive is divided (division) among the different parts of the body. Each part has a job to do and as each part does its special job, it works in harmony with all the other parts. The arrangement of specialized parts within a living thing is sometimes referred to as levels of organization. Cells of course, are the first level of organization. Cells: LOTS of Different Kinds! Here are two examples. Can you guess what kind? Nerve Cells Skin Cells Second Level: Tissues In any multi-cellular organism, cells rarely work alone. Cells that are similar in structure and function are usually joined together to form tissues. Tissues are the second level of organization. There are four basic/major types of tissues in the human body: Muscle tissue, nerve tissue, connective tissue, and epithelial tissue. (There are other kinds of tissues besides these.) Other kinds of tissue include bone tissue (a strong solid tissue that gives you shape and support) made of bone cells in your body form bone tissue. Blood cells in your body are part of blood tissue, a liquid tissue responsible for transporting food and oxygen throughout the body. Let’s Look Again… Here are the cells we saw before, but if you look closely, you can see that they all look similar. Nerve cells working together make nerve tissue, and skin cells make up a special type of epithelial tissue. Taken One At A Time…. Connective tissue connects and supports parts of the body. Blood, fat, ligaments, cartilage, bones, and tendons are all connective tissues. Nerve tissue carries messages back and forth between the brain and every other part of the body. The brain, spinal cord, and nerves are made up of nerve tissue. Epithelial tissue covers and lines the surfaces of your body and organs, inside and out. They primarily serve as protective barriers. Skin is one example. Muscle tissue can contract, or shorten. Because of this, muscle tissue makes parts of your body move. Level Three: Organs When a bunch of different types of tissues work together, they form an organ. There are many organs in the body. How many can you name?? GET IT???? Level Four: Organ Systems Each organ in your body is part of an organ system, a group of organs that work together to perform a major function. For example, your heart is part of your circulatory system, which carries oxygen and other materials throughout your body. Besides the heart, blood vessels are organs that work in your circulatory system. The nervous system detects, interprets, and responds to stimulus outside & inside the body. The circulatory sytem transports blood, gases, nutrients and waste products throughout the body to and from cells. White blood cells fight infections. The excretory system filters harmful wastes from the body. The muscular system enables the body to move. The skeletal system supports and protects the internal organs of the body as well as provide attachment sites for the muscles. The digestive system takes food into the body, breaks the food down into smaller particles, and absorbs the digested nutrients for energy, growth and survival. The respiratory system provides gas exchange between blood and the air. Lungs remove Oxygen from the air and exhale Carbon Dioxide. Let’s Review…. • 1st Level: Cells working together form • 2nd Level: Tissues, which can form • 3rd Level: Organs, which work together to form • 4th Level: Organ Systems, which work together to form • 5th Level: Organisms!