Q.___________ is an exception to Cell Theory.

Before microscopes were good enough to reveal life's inner detail, no one knew that a leaf, a fish and a human being were all built from the same basic material. The cell theory is the great generalisation that finally answered two questions at once: what is every living body made of, and where does every cell come from?

The theory was not the discovery of one person but was assembled and refined over the mid-nineteenth century:

• Matthias Schleiden, a botanist, studied many plants and concluded that all plants are made of different kinds of cells that build up the plant's tissues.
• Theodore Schwann, a zoologist, examined many animal cells, noticed that cells are bounded by a thin outer layer (the plasma membrane), and proposed that the bodies of both animals and plants are made of cells and the products of cells.
• Working together, Schleiden and Schwann formulated the cell theory — but their version had a gap: it did not explain how new cells actually arise.
• Rudolf Virchow closed that gap, showing that cells divide and that every new cell comes from a pre-existing cell — the idea captured in the phrase Omnis cellula-e cellula. This gave the theory its final form.

As understood today, the cell theory rests on two statements:

1. All living organisms are composed of cells and the products of cells.
2. All cells arise from pre-existing cells. …