Here's why:
* Basic Building Block: Cells are the fundamental units of life. All living things are made up of one or more cells.
* Self-Contained Units: Cells carry out all the essential functions of life, such as metabolism, growth, and reproduction, within their own boundaries.
* Variety and Specialization: While all cells share basic features, they can also be highly specialized to perform specific tasks within an organism. For example, nerve cells transmit signals, muscle cells contract, and blood cells transport oxygen.
While smaller structures like organelles exist within cells, they are not considered independent living units.
