Which of the following is not part of the cell theory?
(a) All cells have a nucleus
(b) Cells are the building blocks of life
(c) All cells come from preexisting cells
(d) All organisms are composed of cells.
Answer: (a) All cells have a nucleus
The cell theory is a key concept that forms the basis of most issues in biology, particularly about the structure and functions of living organisms. It consists of three main tenets: Cells are the units of life, all structures of living things are made of cells, and all these cells are produced from other existing cells. However, the statement “all cells have a nucleus” is not formally included in the cell theory nor is it considered one of the postulates of cell theory. This is the case since not all cells contain a nucleus for modulating their activities in the required fashion. Some of the characteristics of cells include prokaryotic cells that lack a membrane-bound nucleus for instance bacteria. Also, it is relevant to understand that mature red blood cells do not have a nucleus in mammals. The cell theory pertains to all life forms, thus giving it credence as the unifying theory of biology depending on the presence or absence of the nucleus in cells.
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