Final answer:
The statement that all living organisms are composed of cells supports the idea that cells are the basic unit of life, as outlined in the cell theory developed by Schleiden, Schwann, and later Virchow. This theory has remained unchallenged in scientific circles since its inception.
Step-by-step explanation:
Support for Cell Theory
The statement that supports the part of the cell theory which says cells are the basic unit of life is that all living things are composed of cells. This is a foundation of the cell theory developed by scientists Matthias Schleiden, Theodor Schwann, and later contributions from Rudolf Virchow. Their unified theory proposed that the cell is the basic unit of structure and function in all living organisms, and this notion has withstood the test of time and scientific scrutiny.
Furthermore, the theory posits that all cells must arise from pre-existing cells, emphasizing the continuity of life. By this logical rule, since all organisms are composed of cells, and no new cells come into being without originating from existing cells, it is indeed factual that the cell is the basic unit of life. It is this continuous cycle of cellular replication that sustains the flow of life across generations.
Not only are cells the simplest, smallest units of life that can carry out all life processes independently, but they also make up the varied and complex organisms we see. The key components such as cytoplasm, plasma membrane, and DNA are present in all cells, providing a consistent blueprint for structure and function in prokaryotic and eukaryotic cells alike.