Levels of Organization Multicellular Organisms:

I. First Level: Cells Cells are the first level or simplest level of organization.

Cells: LOTS of Different Kinds! Nerve CellsSkin Cells

II. Second Level: Tissues B. There are four basic/major types of tissues in the human body: Muscle tissue, nerve tissue, connective tissue, and protective tissue. A. Cells that are similar in structure and function are usually joined together to form tissues.

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 protective 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. Protective 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.

III. Level Three: Organs A. 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??

IV.Level Four: Organ Systems A. Each organ in your body is part of an organ system, a group of organs that work together to perform a major function. There are 11 body systems. 1. For example, your heart is part of your circulatory system, which carries oxygen and other materials throughout your body.

2. The nervous system detects and interprets information from the environment outside the body and from within the body; controls most body functions. 3. The immune system fights disease. 4. The excretory system removes wastes. 5. The endocrine system controls many body processes by means of chemicals, like hormones.

6. The muscular system enables the body to move; moves food through the digestive system, and keeps the heart beating. 7. The skeletal system supports and protects the body, and works with the muscular system to allow movement; makes and stores blood cells and stores some other materials.

8. The digestive system takes food into the body, breaks the food down into smaller particles, and absorbs the digested materials. 9. The respiratory system takes oxygen into the body and eliminates carbon dioxide. 10. The reproductive system produces sex cells that can unite with other sex cells to create offspring; controls male and female characteristics.

10. The integumentary (skin) is the organ system that protects the body from damage, comprising the skin and its appendages (including hair, and nails.)

V. Organism B. Examples: Cat, Human, Bacteria, Virus, Tree A. A Living thing. It can perform life processes on its own. It is the most complex level of organization

Let’s Review…. 1 st Level: Cells working together form 4 th Level: Organ Systems, which work together to form 2 nd Level: Tissues, which can form 3 rd Level: Organs, which work together to form 5 th Level: Organisms: Living Things