Question

1. which part of the cell theory was the first to be established?

cells contain membrane-bound organelles.
cells came from pre-existing cells.
all living organisms are made of cells.
the basic unit of life is the cell.

Explanation:

• In the 17th century, Robert Hooke observed cork cells under a microscope. Later, Matthias Schleiden and Theodor Schwann, in the 19th century, concluded that all plants and animals are composed of cells. This led to the establishment of the idea that all living organisms are made of cells.
• The concept that cells come from pre - existing cells (Virchow, 1855) came after the initial understanding of cell composition.
• The knowledge about membrane - bound organelles developed with the improvement of microscopy and cell biology techniques over time.
• While the cell being the basic unit of life is an important tenet of cell theory, the identification of the presence of cells in all living organisms (by observing various plant and animal tissues) was the first major establishment.

Answer:

All living organisms are made of cells.