Chapter 4, Problem 1TY

The cell theory states that

1. a. all living things are composed of cells.
2. b. cells are the smallest units of living organisms.
3. c. new cells come from pre-existing cells by cell division.
4. d. all of the above.
5. e. only a and b are true.

Summary Introduction

Introduction: Cell theory was given by Schleiden and Schwann along with a contribution from Virchow. Organisms existing in nature can either be unicellular or multicellular. Organisms made up of prokaryotic cells are called prokaryotic organisms and organisms made up of eukaryotic cells are called eukaryotic organisms.

Answer to Problem 1TY

Correct answer: Cell theory states that all living things are composed of cells. Cells are the smallest units of living organisms, and new cells arise from pre-existing cells through cell division. Hence, the correct answer is option d.

Explanation of Solution

Reason for correct answer:

The three parts of cell theory are as follows:

• Cells give rise to all living organisms.
• The smallest units of life for all living organisms are cells.
• Pre-existing cells divide to give rise to new cells with the help of cell division.

Option d. is given as “all of the above”.

According to the cell theory, the smallest units of living organisms are cells. All living things are composed of cells and pre-existing cells give rise to a new cell after undergoing cell division. Hence, the correct answer is option d.

Reasons for incorrect answer:

Option a. is given as, “all living things are composed of cells”.

Cell theory states that “all living organisms are composed of cells”. However, it also states that the smallest units of life are cells and new cells are formed when pre-existing cells undergo cell division. Hence, option a. is incorrect.

Option b. is given as, “cells are the smallest units of living organisms”.

Cell theory states that “cells are the smallest units of living organisms”. However, it also states that cells are the basic unit of all living organisms, and cell division gives rise to new cells from pre-existing cells. Hence, option b. is incorrect.

Option c. is given as, “new cells come from pre-existing cells by cell division”.

Cell theory states that the pre-existing cells give rise to new cells after undergoing cell division. However, it also states that cells are the smallest units of life and they give rise to all living organisms. Hence, option c. is incorrect.

Option e. is given as, “only a and b are true”.

Schleiden and Schwann postulated that cells give rise to all living organisms and are the smallest units of life. However, the contributions of Virchow who said that new cells arise from pre-existing cells through cell division is also added to the cell theory. Hence, option e. is incorrect.

Hence, the options a., b., c., and e. are incorrect.

Conclusion

Thus, according to the cell theory, cells are the smallest units of living organisms, all living organisms are made of cells, and pre-existing cells divide to form new cells.