MICROORGANISMS

HOW LIVING THINGS ARE ORGANIZED

Multicellular living things are very organized. In fact, levels of organization exist:

The smallest living unit that makes up a living thing is the CELL.
Look at these human cells:

CELLS group together to form tissues.

TISSUES are made up of similar cells that carry out a common function. For example, muscle tissue is made up of hundreds of muscle cells grouped together.

 Tissues form ORGANS. Organs are made up of a group of tissues that work together to carry out a common function. For example, muscles and bones are organs.

Organs form SYSTEMS. Systems are made up of a group of organs that work together to carry out a common function. For example, the skeletal system is made up of bones.

When all systems work together, they form an ORGANISM. An organism is a COMPLETE LIVING THING.