During which process do individual tissues form from a mass of cells?

The correct answer is related to the process of gastrulation, which is a critical phase in embryonic development. During gastrulation, a single-layered blastula reorganizes into a multilayered structure called the gastrula. This process establishes the three primary germ layers: the ectoderm, mesoderm, and endoderm, which eventually differentiate into various tissues and organs in the developing organism.

Gastrulation is crucial for the formation of individual tissues because it lays the groundwork for organogenesis—the process where different tissue types arise from these layers. Through this reorganization, cells gain specific identities and functions, which is essential for the proper formation and functionality of the body systems.

Other processes mentioned, like meiosis and mitosis, involve cell division but do not directly relate to the formation of different tissues from a mass of cells. Meiosis is a form of cell division that produces gametes for sexual reproduction, while mitosis is responsible for cell replication and tissue growth. Differentiation, while it does involve the specialization of cells into various types, is a broader term that encompasses the processes that occur after gastrulation, leading to the final development of tissues and organs.