Question 18

The fundamental unit of life that constructs all living organisms is the cell.

Cells are the basic building blocks of all living organisms, serving as the smallest unit capable of performing life functions.

A) Atom

Atoms are the basic units of matter and the building blocks of molecules, but they do not represent the smallest unit of life. While atoms combine to form cells, they are not capable of performing the functions necessary for life on their own.

B) Cell

Cells are indeed the fundamental unit of life. They are the smallest structures that can carry out all life processes, including metabolism, growth, and reproduction. Every organism, whether unicellular or multicellular, is made up of cells, making this option the correct answer.

C) Organ

Organs are complex structures composed of different types of tissues that work together to perform specific functions within an organism. While organs are essential for the functioning of multicellular organisms, they are not the basic unit of life; that role belongs to cells.

D) Tissue

Tissues are groups of cells that work together to perform a specific function, but they are not the fundamental unit of life. Like organs, tissues are made up of cells, meaning they rely on cells as the basic building blocks for their structure and function.

Conclusion

The cell is the fundamental unit of life, as it is the smallest entity capable of all life processes. Atoms, organs, and tissues, while important in biological organization, do not fulfill the criteria of being the basic unit of life, thus affirming that option B is the only correct answer.