What branch of zoology studies the early development of living organisms?

Embryology is the branch of zoology that focuses specifically on the early development of living organisms, particularly from fertilization to the formation of key structures. It examines the processes that dictate how cells divide, differentiate, and organize into complex tissues and organs, shaping the organism's development. This field of study helps scientists understand not only the development of specific species but also the evolutionary relationships and developmental processes that various organisms share.

In contrast, genetics studies heredity and the variation of organisms, focusing primarily on the roles of genes and DNA. Ecology investigates the relationships between living organisms and their environments, including interactions and ecosystems. Physiology examines the normal functions of living organisms and their parts, focusing on physical and biochemical processes. While all these fields are interconnected, embryology is distinct in its direct focus on developmental processes.