Which process is essential for the growth and repair of multicellular organisms?

Mitosis is the process that is fundamental for the growth and repair of multicellular organisms. It involves the division of a single cell into two identical daughter cells, allowing for an increase in the number of cells. This process is crucial for growth as it helps organisms develop from a single fertilized egg into a mature individual, providing the necessary cellular expansion to form tissues and organs. Furthermore, mitosis plays a vital role in the repair of tissues; for instance, when an organism sustains an injury, mitosis helps regenerate the damaged cells, restoring the tissue's structure and function.

Meiosis, on the other hand, is specialized for sexual reproduction and results in gametes, which are not involved in growth or tissue repair. Binary fission is a form of asexual reproduction seen in prokaryotic organisms, such as bacteria, and is not applicable to the growth of multicellular organisms. Regeneration refers to the process where certain organisms can regrow lost parts or tissues, but it is not the primary mechanism for growth in multicellular organisms. Instead, mitosis is a universal process present in nearly all eukaryotic cells that directly contributes to their growth and maintenance.