According to cell theory, what is the relationship between organisms and cells?

• A. Each organism is made of cells
• B. Cells cannot interact with other cells
• C. Only animals are made of cells
• D. Cells do not form tissues

Answer: (A)

The main idea here is that organisms are built from cells, with cells as the basic units of life. According to cell theory, all living things are composed of cells, and new cells arise from existing cells. In multicellular organisms, cells specialize and arrange themselves into tissues, organs, and then the whole organism, showing how the organism is essentially a collection of cells working together. This makes the relationship clear: every organism is made up of cells.

The other statements don’t fit this view. Cells can communicate and interact with one another to coordinate functions, so the claim that they cannot interact is incorrect. Many living things other than animals—plant and fungal cells, as well as bacteria—are also composed of cells, so “Only animals are made of cells” isn’t true. And in multicellular organisms, cells do form tissues, which contradicts the idea that cells do not form tissues.