Answer

Inverts and Vertebrates

Q1.      A chordate refers to any animal from the phylum chordata including the protochordates and vertebrates. The four main characteristics that are common in all chordates include a dorsal hollow nerve cord, a notochord, pharyngeal slits, and a post-anal tail (Janvier, 2015). The dorsal hollow nerve cord develops into the spinal cord and brain in most chordate embryos. On the other hand, the notochord serves as a cite for muscle attachment and a source of midline signals during development. In contrast, the pharyngeal slits are used to filter water and food particles in primitive chordates (Janvier, 2015). Lastly, the post-anal tail is used for balance, courting, and locomotion in some vertebrates and aquatic species. All these features are often present during the embryonic development stage.

Q2.      Starfish and chordates are closely related for a number of reasons. For instance, they are both classified as deuterostomes because their mouth develops separately from the blastopore such that their anus forms first before the mouth (Lowe et., 2015). Similarly, they both have a radical and intermediate cleavage where the cells remain homogenous until a later developmental period (Janvier, 2015). Moreover, the two share a closely related evolutionary relationship.

Q3.      The amphibians use both their lungs and skin for respiration. In this case, the skin has to remain moist for them to absorb oxygen. As a result, the amphibians secrete mucous to keep their skin wet (Naguib & Reid, 2015). Once the oxygen is absorbed through the skin it is transported to the rest of the body through the blood vessels (Naguib & Reid, 2015).  However, the tadpoles and a number of aquatic amphibians use gills like fish to breath.