Which scientist proposed that animals are made of cells?

• A. Hooke
• B. Leeuwenhoek
• C. Schwann
• D. Virchow

Answer: (C)

The main idea here is how the cell theory was developed and who extended it to animals. Theodor Schwann is the scientist who proposed that animals are made of cells, showing that animal tissues are organized into individual cells just like plant tissues, which Schleiden had already described for plants. Hooke did important early work by naming the cell after viewing cork, but he didn’t state that animals are composed of cells. Leeuwenhoek focused on observing microorganisms and improving microscopy, not on formulating the cell-based view of animals. Virchow added the idea that cells come from preexisting cells, reinforcing cell theory, but he didn’t make the claim that animals are built from cells. So, Schwann is the best answer because he explicitly extended the concept of cells to animals.