Which is the building block of all organisms and the smallest unit of life?

Which is the building block of all organisms and the smallest unit of life?

• A. Tissue
• B. Organ system
• C. Cell
• D. Organ

Answer: (C)

Life begins at the cellular level. A cell is the smallest unit that can carry out the essential processes that define life—metabolism, growth, response to the environment, and reproduction. All organisms are built from cells, from single-celled bacteria to complex multicellular beings. Cells combine to form tissues, tissues build organs, and organs form organ systems that sustain the organism. Because of this, the cell is the building block of all organisms and the smallest unit of life. (Note: some definitions note that certain entities like viruses challenge the idea of being truly alive on their own, but within living organisms, the cell is the basic unit.)

Life begins at the cellular level. A cell is the smallest unit that can carry out the essential processes that define life—metabolism, growth, response to the environment, and reproduction. All organisms are built from cells, from single-celled bacteria to complex multicellular beings. Cells combine to form tissues, tissues build organs, and organs form organ systems that sustain the organism. Because of this, the cell is the building block of all organisms and the smallest unit of life. (Note: some definitions note that certain entities like viruses challenge the idea of being truly alive on their own, but within living organisms, the cell is the basic unit.)