What is the primary characteristic of multicellular organisms?

Multicellular organisms are defined by their structure, which consists of multiple cells that are organized into tissues and organs. This organization allows for a higher level of complexity and specialization compared to unicellular organisms, where a single cell carries out all functions necessary for life. In multicellular organisms, cells can perform specialized roles, such as muscle cells for movement or nerve cells for transmitting signals, which contribute to the overall functioning and survival of the organism.

This characteristic enables multicellular organisms to perform functions that individual cells cannot, such as maintaining homeostasis, responding to environmental changes, and developing into larger and more complex life forms. Tissues, made up of groups of similar cells, work together to form organs, which then integrate to create systems that perform critical biological processes. This hierarchical organization is fundamental to the functioning of all multicellular life.