Question

“Each cell leads a double life” was first proposed by
A. Schleiden
B. Grew
C. Von Mohl
D. Malpighi

Answer 1

Hint: In biology, the cell is the essential membrane-bound unit containing the fundamental molecules of life that make up all living things. A single cell, such as a bacterium or yeast, is also a complete organism in itself. As they mature, other cells develop specialised roles. Along with other specialised cells , these cells become the building blocks of large multicellular organisms, such as humans and other animals.

Complete answer:
During the nineteenth century, Matthias Jacob Schleiden helped develop the theory of cells in Germany. As a common element among all plants and animals, Schleiden studied cells. Through his invention of the Zeiss microscope lens and through his work with cells and cell theory as an organising principle of biology, Schleiden contribute to the field of embryology.
The theory of cells notes that living things consist of one or more cells, that the basic unit of life is the cell, and that cells derive from existing cells. Botanist Matthias Schleiden and zoologist Theodor Schwann were researching tissues at the end of the 1830s and suggested the unified theory of cells. The unified theory of cells notes that: one or more cells are composed of all living things; the cell is the fundamental unit of life; and from existing cells emerge new cells. Rudolf Virchow made major contributions to this theory later on. Schleiden and Schwann proposed a theory of cells that stated that each cell is itself an entity with all life attributes. Each cell is living both its individual existence and as a tissue community that has become an integral part of the plant. So Schleiden discovered this double life of each cell while studying plant cells.

Hence, the correct answer is (A).

Note:
As the mechanism for cell origination, Schleiden and Schwann suggested spontaneous generation, but spontaneous generation, also called abiogenesis, was later disproved. "All cells only emerge from pre-existing cells," Rudolf Virchow famously said. However, the portions of the theory that did not have to do with cell origin were up to scientific review and are generally agreed upon today by the scientific community.