Final answer:
Robert Hooke first described cells in 1665, while Matthias Schleiden and Theodor Schwann later proposed that cells are the fundamental units of both plants and animals. Rudolf Virchow expanded on this by stating that cells arise from existing cells, finalizing the key aspects of the cell theory.
Step-by-step explanation:
Contributions to Cell Theory
Robert Hooke first coined the term “cell” in 1665 when observing cork tissue, describing the box-like structures he observed. However, the scientific community did not immediately recognize the significance of these structures as the fundamental units of life.
Late in the 1830s, Matthias Schleiden, a botanist, observed plant tissues and noted that they were made up of cells, although he incorrectly believed that cells formed through crystallization.
Simultaneously, Theodor Schwann, a zoologist, also studied cells and concurred with Schleiden that animals and plants were made up of cells, proposing a unified theory that cells are the basic building blocks of all life forms.
Building upon their work, Rudolf Virchow later contributed to the cell theory by observing cell division in 1858 and proposing that new cells arise from pre-existing cells, a critical addition to the understanding of cell reproduction.
The combined findings of these scientists helped form the cell theory, which states that all living organisms are composed of one or more cells, the cell is the basic unit of life, and that cells arise from existing cells.