Final answer:
Cells are called the building blocks of an organism because they are the smallest unit of a living thing, and all living things are made up of cells.
Step-by-step explanation:
Cells are deemed the building blocks of organisms due to their fundamental role in the structure, function, and continuity of life. They are the smallest units of living matter, possessing the ability to carry out essential processes such as metabolism, growth, and reproduction. The diverse array of cell types, each specialized for specific functions, collectively forms tissues, organs, and systems within an organism.
Cells share common features, such as a cell membrane, genetic material, and the capacity for self-replication. This hierarchical organization, with cells as the foundational units, underscores their pivotal role in shaping the complexity and functionality of living organisms.