A deuterostome is a group of animals characterized by their embryonic development. In deuterostomes, the first opening that forms during the early stages of development becomes the anus, while the mouth develops later. This contrasts with protostomes, where the mouth forms first. Deuterostomes include major groups such as chordates, which encompass vertebrates like mammals and birds, and echinoderms, such as starfish and sea urchins. Deuterostomes are significant in the study of evolutionary biology due to their diverse forms and complex structures. They exhibit a wide range of body plans and adaptations, making them an essential focus for understanding the evolution of multicellular life. Their unique developmental processes also provide insights into the relationships between different animal groups.