In 1838 botanist Matthias Schleiden determined that all plants are composed of cells. In 1839 anatomist Theodor Schwann proposed that all animals are composed of cells. In 1855 biologists Rudolph Virchow added to Schleiden & Schwann’s observations and proposed that all living things are composed of cells. Which statement is also part of Virchow’s theory? Group of answer choices all cells have a cell wall all cells can develop into any other type of cell all cells come from pre-existing cells all cells are capable of photosynthesis