
Concept explainers
The cell theory states that
- all living things are composed of cells.
- cells are the smallest units of living organisms.
- new cells come from pre-existing cells by cell division.
- all of the above.
- a and b only.

Introduction:
The cells form aggregate to function as individual unit called a tissue. The tissues of different types regulating one specific function forms organs and various organs destined to control an individual system form organ system of the body.
Answer to Problem 1TY
The correct answer is option (d) all of the above.
Explanation of Solution
Explanation/justification for the correct answer:
Option (d) all of the above.The cell theory states that all living organisms are made up of cells that are the smallest and the most fundamental unit of the living organism. The cells arise from already existing cells as a result of cell division. These three postulates define cell theory. So, the correct answer is option (d).
Explanation for incorrect answer:
Option (a) all living cells are composed of cells.The cell theory states three postulates and explains that all living organisms are made up of cells, but this in only the only postulate of cell theory. So, this is an incorrect option.
Option (b) cells are the smallest units of living organisms.According to cell theory the cells are the most fundamental and smallest component of the living organisms, but this is not the only postulate of cell theory. So, this is an incorrect option.
Option (c) new cells arise from pre-existing cells by cell division.New cells arise from pre-existing cells is the postulate of cell theory given by Rudolf Virchow, but this is not the only postulate of cell theory. So, this is an incorrect answer.
Option (e) a and b only. According to cell theory the living organisms are made up of cells and the new cells come from pre-existing cells through cell division but there is also a third postulate stating that cells are the smallest unit of living organism. So, this is an incorrect answer.
The cell theory states that all living cells are made up of smallest unit called cells that arise from pre-existing cells through cell division. Hence, the correct answer is option (d) all of the above.
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Chapter 4 Solutions
Principles of Biology
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