Which process refers to changes that cause an organism to grow into a more complex form?

The process that refers to changes causing an organism to grow into a more complex form is development. Development encompasses the series of changes an organism undergoes from a single fertilized egg to a mature individual, including cellular division, differentiation, and growth.

During development, an organism goes through specific stages, each marked by unique structural and functional characteristics. For example, in animals, this includes stages such as the embryonic stage, infant stage, and adulthood, where tissues and organs become more sophisticated and specialized.

In contrast, evolution refers to the gradual change of species over time, driven by processes such as natural selection, which does not specifically pertain to the individual growth of an organism. Adaptation involves changes that lead to greater survival and reproductive success in specific environments, while reproduction is the biological process through which new individuals are generated. Thus, the concept of development is closely tied to the individual organism's maturation and the increasingly complex structures that emerge through various life stages.