What are the basic units of all living things, from bacteria to plants to humans?

What are the basic units of all living things, from bacteria to plants to humans?

• A. Cells
• B. Organelles
• C. Tissues
• D. Organs

Answer: (A)

The basic unit of life is the cell. Bacteria are single-celled organisms, so life is carried out by one cell. Plants and humans are multicellular and built from countless cells that organize into tissues and organs to perform specialized functions. Organelles are the structures inside cells, not independent living units. Tissues are groups of similar cells working together, and organs are assemblies of tissues with specific roles. This idea—cells as the fundamental units of life—comes from cell theory, which also notes that new cells arise from existing cells.

The basic unit of life is the cell. Bacteria are single-celled organisms, so life is carried out by one cell. Plants and humans are multicellular and built from countless cells that organize into tissues and organs to perform specialized functions. Organelles are the structures inside cells, not independent living units. Tissues are groups of similar cells working together, and organs are assemblies of tissues with specific roles. This idea—cells as the fundamental units of life—comes from cell theory, which also notes that new cells arise from existing cells.