Differences In Animal Phyla Essay -- essays research papers

Because they be 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 embryonal 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 slake 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, the embryo becomes layered through the mould of gastrulation, or the formation of the cardinal layered, cup-shaped embryonic stage from a blastula. These layers are called germ layers. Most animals are triploblastic, meaning they have three germs layers. These are the exoderm, the endoderm, and the mesoderm. The ectoderm is the outermost layers which forms the bodys covering and the central nervous system. The endoderm is the innermost germ layer. It forms the digestive tube and gives rise to most organs. The third layer, the mesoderm, exists amidst the endoderm and ectoderm. It forms the muscles and most other organs towards the upper layer of the animal. Diploblastic animals, or animals with only two germ layers, lack mesoderm. There are only two diploblastic phyla Porifera, the sponges, and Cnidaria, the bag animals. All other animals are ...