What are the key transitions in body design that are responsible for most of the differences of Eumetazoa? 

The first key transition in the animal body plan is the presence of tissues in the Eumetazoa. The presence of tissues is one of the major differences between protozoa and other animals. All animals that are classified as Eumetazoa have definite shape and symmetry. It is either they are radially symmetrical or bilaterally symmetrical.

Animals that are radially symmetrical have all parts of their body arranged to a central axis, while those that are bilaterally symmetrical have a body plan where the right half is the mirror image of the left half, vice versa. Any key difference is the presence of a body cavity.

This creates an internal space where different organs of the body are placed. The fourth key transition in the animal body is the subdivision of the body into different segments. Other key transitions in the animal body are deuterostome development and molting.

The answer to this is distinct tissues. A lot of people are not too familiar with distinct tissues but actually, these are issues that can be found in most animals. This is considered to be a tissue or even organ printing approach so that particular pieces can be formed. Do remember that there are different types of basic tissues that are available and each type of tissue will have its own qualities.

For example, the connective tissue will make sure that all of the tissues are properly bounded. The epithelial tissues are in charge of providing enough coverage and also extra protection. The muscle tissue will make up the muscles and so on and so forth.

The critical transitions in body design include the evolution of tissues. The Eumetazoa has distinct tissues with highly specialized cells. The development of bilateral symmetry. Sponges do not have any definite symmetry, as they grow as irregular masses. Radial symmetry is where symmetrical bodies first evolved in marine animals demonstrating radial symmetry.

The parts of their bodies are interestingly positioned around the central axis. Bilateral symmetry is a unique form of organization that allows portions of the body to evolve differently, permitting various organs in other parts of the body. They can move around better than radially symmetrical ones. Due to their enhanced mobility, bilaterally symmetrical animals are adept in seeking food, finding mates, and avoiding predators—the evolution of body cavity.

The presence of a body cavity allows for an improved digestive tract. It also allows for more space to collect many eggs and sperm. The fourth key transition is the evolution of segmentation, where the animal body plan involved subdivisions of the body—the evolution of molting. The animal must shed its hard exoskeleton—the evolution of deuterostome development. Bilateral animals are separated into two groups, including Protostomes and deuterostomes.