HESI A2 Biology Practice Test 2025 – All-in-One Study Guide for Exam Success!

The cell is recognized as the fundamental unit of biology because it is the smallest living entity that can perform all the processes necessary for life. This includes metabolism, growth, response to stimuli, and reproduction. Each type of cell serves specific functions in living organisms, and they are the building blocks from which tissues, organs, and ultimately whole organisms are formed.

In multicellular organisms, tissues are made up of groups of similar cells that work together for a common function, and organs are composed of multiple types of tissues functioning together. An organism is a complete living entity that may be unicellular or multicellular, but it is composed of various cells working in harmony. Understanding that the cell is the foundational unit underlines its importance in biology, as it relates to everything from cellular processes to the complexity of life itself.