Final answer:
The events from fertilization to full formation of an animal are termed embryonic and fetal development, encompassing stages from the initial cell divisions post-fertilization to the maturation of organ systems before birth.
Step-by-step explanation:
The events that occur from the time of fertilization up until an animal is fully formed are referred to as embryonic and fetal development. This complex process consists of several key stages including the germinal stage, the embryonic stage, and the fetal stage.
Initially, the germinal stage begins with fertilization and proceeds through early cell divisions, with the zygote forming into a blastocyst, which eventually implants in the uterus. Subsequently, the embryonic stage spans from implantation to about the eighth week, where significant growth and morphological changes occur through processes like gastrulation, neurulation, and organogenesis.
Gestation is the term for the entire period in utero. Following the embryonic stage, the developing human is called a fetus, marking the fetal stage from the ninth week until birth where the organ systems continue to develop and mature. In essence, developmental biology underscores the remarkable journey from a single cell to a complex, multi-cellular organism.