Because they are grouped in the same kingdom, the nine animal phyla share the same fundamental characteristics- they are multicellular, heterotrophic eukaryotes that obtain nutrients through ingestion, they lack cell walls, they have nervous tissue and muscle tissue, and they reproduce sexually and have a unique embryonic life cycle. However, the animal phyla have a great number of differences as well. Some are visible to the naked eye, while others are less obvious, and still more cannot even be seen after embryonic development. What are these differences, and how did they shape the development of the phylogenetic tree? In animals,...
of this type of symmetry is a jellyfish. It is symmetrical when viewed from above or below. Bilateral symmetry is two-sided symmetry. Bilateral animals are symmetrical when "cut" in half from above or below. Cephalization in this group has created a clearly visible head, and when divided, the head section is called the animal's anterior, the tail it's posterior, and the top and bottom are called the dorsal and ventral sides. Most animals possess bilateral symmetry, but that does not mean that all remaining animals are radial. A few, such as sponges and some types of gastropods are asymmetrical.