What is the smallest unit of life that can replicate independently?

The smallest unit of life that can replicate independently is a cell. Cells are the fundamental building blocks of all living organisms. Each cell has the ability to perform essential life functions, including growth, metabolism, and reproduction. During the process of cell division, a single cell can replicate itself, giving rise to two daughter cells, thereby ensuring the continuation of life.

Other choices such as an atom, tissue, and molecule do not meet the criteria for being independently replicating units of life. Atoms are the basic units of matter and form molecules, but they do not exhibit life characteristics such as metabolism or reproduction. Tissues are groups of similar cells working together to perform a specific function but cannot replicate on their own since they are made up of multiple cells. Molecules are chemical structures formed from atoms, and while some molecules are essential for life (like DNA and proteins), they do not have the capacity to replicate independently as living organisms do. Thus, the cell stands out as the essential unit capable of independent replication and sustaining life processes.