AP BIOLOGY

Detailed explanation-1: -The third part, which asserts that cells come from preexisting cells that have multiplied, was described by Rudolf Virchow in 1858, when he stated omnis cellula e cellula (all cells come from cells).

Detailed explanation-2: -In 1855, he further developed his ideas by publishing his famous aphorism omnis cellula e cellula which became a part of the foundation for cell theory. Virchow’s theory stated that just as animals are unable to arise without previously existing animals, cells are unable to arise without previously existing cells.

Detailed explanation-3: -Credit for developing cell theory is usually given to three scientists: Theodor Schwann, Matthias Jakob Schleiden, and Rudolf Virchow. In 1839, Schwann and Schleiden suggested that cells were the basic unit of life. Their theory accepted the first two tenets of modern cell theory (see next section, below).

Detailed explanation-4: -It is not entirely accurate to attribute all of cell theory to Rudolf Virchow. Cells were first observed by Robert Hooke in 1665, determined to be alive by Anton van Leeuwenhoek by 1674, and considered to be the fundamental building block of life by 1839, thanks to Matthias Schleiden and Theodor Schwann.