Lesson 4: Levels of Organization

The basic building blocks of all living things. They carry out essential functions and can exist independently (like bacteria) or as part of a larger organism.

Groups of similar cells that work together to perform a specific function. Examples include muscle tissue, nervous tissue, and epithelial tissue.

Structures made up of different tissues that work together to perform complex functions. Examples include the heart, lungs, and liver.

Groups of organs that work together to carry out major bodily functions. Examples include the digestive system, respiratory system, and circulatory system.