BIOL 1108 Lecture Notes - Lecture 37: Dorsal Nerve Cord, Axial Skeleton, Matrotrophy
Document Summary
Animal evolution - the deuterostomes and the chordates. Hemichordates are are marine deposit feeders and filter feeders and are the sister group to the echinoderms. Echinoderms (phylum echinodermata) are unsegmented deuterostomes with radial symmetry and an endoskeleton. Chordates are bilaterally symmetric, segmented deuterostomes with a notochord and pharyngeal slits. The tunicats, lancelates, and the hagfish are chordates without backbones. The vertebrates (vertebrata) have a jointed axial skeleton. The chondrichthyes and the osteichthyes are gnathostomes with jaws, paired fins, and calcified skeletons. Endothermy and matrotrophy evolved repeatedly in the vertebrates. The amphibia are tetrapods that remain dependant on free water for reproduction. Tetrapods that retain internal water in the egg. Three major phyla of the deuterostome tree. Marine dwelling bottom feeders or filter feeders. Not the same body plan as the other deuterostomes. Echinoderm larvae are bilaterally symmetric, and adults are pentaradially symmetrical. Unclear whether this lack of segmentation is ancestral or derived. Skeletons are really interlocking calcium carbonate plates.
