PLZWRITE A THREE SENTANCE LOGICAL SUMMARY FOR THIS PEICE OF TEXT When the English scientist Robert Hooke used a crude microscope to observe a thin slice of cork in 1665, he saw “a lot of little boxes.” The boxes reminded him of the small rooms in which monks lived, so he called them cells. Ten years later, the Dutch scientist Anton van Leeuwenhoek used a microscope to view water from a pond and his own dental scrapings, and discovered many living creatures; he named them “animalcules,” or tiny animals. Today we know that they were not animals but single-celled organisms known as bacteria.
It took scientists more than 150 years to fully appreciate the discoveries of Hooke and Leeuwenhoek. In 1838, the German botanist Matthias Schleiden concluded that cells make up not only the stems and roots but every part of a plant. A year later, the German zoologist Theodor Schwann claimed that animals are also made of cells. In 1858, Rudolph Virchow, a German physician, determined that cells come only from other cells. The observations of Schleiden, Schwann, and Virchow form the cell theory, which has three parts:
1. All living things are made of one or more cells.
2. Cells are the basic units of structure and function in organisms.
3. All cells arise from existing cells.