Opisthokonta
Opisthokonta: Metazoa II: Eumetazoa: Bilateria: Protostomia: Ecdysozoa
Objectives: • Know the key features of the Phylum Nematoda. Know how they relate to other metazoan phyla. • List the key characteristics of the Phylum Arthropoda. Identify examples. List the four subphyla and their key distinguishing features. Identify examples of the subphyla Chelicerata, Crustacea, Myriapoda, and Hexapoda. • Be able to identify the different structures on these organisms and understand their function. • Understand differences between terrestrial versus aquatic arthropods (e.g., grasshoppers versus crawfish) and how that relates to environment in which they live. • Define and be able to apply the terms in bold found throughout this exercise. Introduction: Our survey of metazoan diversity continues with the clade Bilateria, which consists of animals which have bilaterally symmetrical body plans, unlike the radially symmetrical Phylum Cnidaria and the largely asymmetrical Phylum Porifera. Additionally, members of this clade are triploblastic, meaning that they have three embryonic tissue layers from which structures and organs develop, in contrast to the diploblastic cnidarians. The clade Bilateria can itself be divided into two additional clades based on differences in developmental pathways: protostomes and deuterostomes. At an early stage of embryonic development, around the 128–cell stage, eumetazoans form a hollow sphere of cells referred to as a blastula. In the next developmental step, cell divisions on one side of the sphere result in inward growth toward the hollow interior of the sphere. This developmental step is known as gastrulation, the embryonic stage is known as the gastrula, and the initial opening on the outside of the sphere of cells where the inward growth is known as the blastopore. In most bilaterian animals, the inward growth continues and emerges as a second opening on the opposite side of the gastrula. In protostomes, the blastopore will develop into the
Objectives: • Know the key features of the Phylum Nematoda. Know how they relate to other metazoan phyla. • List the key characteristics of the Phylum Arthropoda. Identify examples. List the four subphyla and their key distinguishing features. Identify examples of the subphyla Chelicerata, Crustacea, Myriapoda, and Hexapoda. • Be able to identify the different structures on these organisms and understand their function. • Understand differences between terrestrial versus aquatic arthropods (e.g., grasshoppers versus crawfish) and how that relates to environment in which they live. • Define and be able to apply the terms in bold found throughout this exercise. Introduction: Our survey of metazoan diversity continues with the clade Bilateria, which consists of animals which have bilaterally symmetrical body plans, unlike the radially symmetrical Phylum Cnidaria and the largely asymmetrical Phylum Porifera. Additionally, members of this clade are triploblastic, meaning that they have three embryonic tissue layers from which structures and organs develop, in contrast to the diploblastic cnidarians. The clade Bilateria can itself be divided into two additional clades based on differences in developmental pathways: protostomes and deuterostomes. At an early stage of embryonic development, around the 128–cell stage, eumetazoans form a hollow sphere of cells referred to as a blastula. In the next developmental step, cell divisions on one side of the sphere result in inward growth toward the hollow interior of the sphere. This developmental step is known as gastrulation, the embryonic stage is known as the gastrula, and the initial opening on the outside of the sphere of cells where the inward growth is known as the blastopore. In most bilaterian animals, the inward growth continues and emerges as a second opening on the opposite side of the gastrula. In protostomes, the blastopore will develop into the