Complete the chart of body cavity and germ layer and phylum
Answers
The following phyla of multicellular animals (called metazoans) are usually included in general biology courses. Remember that the botanical counterpart of a phylum is called a division. Unicellular animals (called protozoans) are usually placed in the kingdom Protista along with the divisions of unicellular and multicellular algae. True multicellular animals are typically without cellulose cell walls and photosynthetic pigments, and they form diploid embryos developing from a blastula stage. The blastula is a hollow, fluid-filled sphere bounded by a single layer of cells surrounding a central cavity or blastocoel. The blastula develops from a spherical cluster of cells called a morula. In addition, animals are capable of locomotion or body movement by means of contractile muscle tissue. In a cross sectional view, animal embryos are composed of an outer layer called ectoderm, a middle layer or mesoderm, and an internal layer or endoderm that surrounds the digestive cavity. Multicellular animals are heterotrophic by ingestion of food into a body cavity (coelom) that is completely lined by the mesoderm. Primitive phyla without a true coelom include the Porifera and Coelenterata (Cnidaria).