| A | B |
|---|
| cell | The basic unit of structure and function of living things. |
| microscopic | Too small to be seen without using a microscope. |
| organism | Any living thing that maintains vital life processes. |
| cell membrane | The thin covering that surrounds every cell. |
| nucleus | The part of a cell that directs all of the cell's activities. |
| cytoplasm | The jellylike material inside a cell between the cell membrane and the nucleus |
| protist | A simple, single-celled or multi-celled organism with a nucleus and organelles. |
| tissue | A group of cells that work together to perform a certain function. |
| organ | A group of tissue that work together to perform a certain function. |
| organ system | A group of organs that work together to do a job for the body. |
| digestive system | The organ system that turns food into nutrients that body cells need for energy, growth, and repair. |
| circulatory system | The organ system made up of the heart, blood vessels, and blood that transports materials throughout the body. |
| respiratory system | The organ system, including the lungs, that exchanges oxygen and carbon dioxide between the body and the environment. |
| skeletal system | The organ system, including the bones, that protects the body and gives it structure. |
| muscular system | The organ system, that includes the muscles and allows the body to move. |
| nervous system | The organ system-including the brain, spinal cord, and nerves that senses your surroundings and controls other organs. |
| excretory system | The organ system, including the kidneys and bladder, that removes waste materials from the blood. |
