The smallest structural and functional unit of life isA. OrganB. CellC. TissueD. Organ system

The question asks about the smallest structural and functional unit of life. Let us analyze each option to determine the correct answer.

A. Organ
An organ is a group of tissues that work together to perform a specific function. Examples include the heart, liver, and lungs. Organs are made up of smaller components, so they cannot be considered the smallest unit of life.

B. Cell
A cell is the basic structural and functional unit of life. All living organisms are made up of one or more cells, and all vital processes of life occur within cells. It is the smallest unit that can independently carry out all life processes.

C. Tissue
A tissue is a group of similar cells that work together to perform a specific function. For example, muscle tissue consists of muscle cells. Since tissues are made up of cells, they are not the smallest unit.

D. Organ system
An organ system is a group of organs that work together to perform a complex function, such as the circulatory system or digestive system. It is composed of multiple organs and therefore cannot be the smallest unit.

Correct answer: B. Cell

Explanation: The cell is the smallest structural and functional unit of life because it is the simplest unit that can perform all life processes, including metabolism, growth, and reproduction. This is true for both unicellular organisms (e.g., bacteria) and multicellular organisms (e.g., humans).