Embryology is the study of what?

Embryology is fundamentally concerned with the development of an organism's embryo from fertilization through to fetal development. This branch of biology examines the various stages of embryonic growth, the differentiation of cells, the formation of tissues, and the major organs that develop within an embryo. Understanding embryonic development is crucial for many areas of biology, including genetics, developmental biology, and medicine, as it can provide insights into congenital disorders and the mechanisms underlying normal development.

The other choices focus on different aspects of biology. While genetic mutations in adults examine the stability and changes in DNA in fully formed organisms, the evolutionary history of species relates to phylogenetics and the history of life's diversification over time, straying from embryonic development. Additionally, the physiology of mature organisms pertains to how fully developed organisms function, rather than the early stages of life. Thus, the focus of embryology exclusively aligns with the growth processes and transformations that occur during the embryonic phase of development.