The Levels of Organization:

Tissue:

  • Made up of cells that are similar in structure and function and which work together to perform a specific activity
  • Examples - blood, nervous, bone, etc.

Organs:

  • Made up of tissues that work together to perform a specific activity
  • Examples - heart, brain, skin, etc.

Organ Systems:

  • Groups of two or more tissues that work together to perform a specific function for the organism.
  • Examples - circulatory system, nervous system, skeletal system, etc.

Organisms:

  • Entire living things that can carry out all basic life processes. Meaning they can take in materials, release energy from food, release wastes, grow, respond to the environment, and reproduce.
  • Usually made up of organ systems, but an organism may be made up of only one cell such as bacteria or protist.
  • Examples - human, animal, and single cells

All these levels work together to make the body work and function correctly and they make the body the way it is now. If you took any of the levels away then the body wouldn't work the same. If you took out the Organs, then the body couldn't function inside. If you took out the Organ Systems, then none of the systems inside or out of the body would be able to move or work anymore.

Cells:

  • Are the basic unit of structure and function in living things.
  • May serve a specific function within the organism
  • Examples- blood cells, nerve cells, bone cells, etc.