1 8 3 Brains BIO 361T Fall 2014 1 True or False If false give a counter example and correct the statement a All chordates are vertebrates False most are not sea squirts or lancelets b All vertebrates are chordates True c All deuterostomes are segmented False most are not Echinodermata like star fish d All segmented animals are deuterostomes False segmentation arose independently in the lineage leading to Annelids and Arthropods e There are no radially symmetrical Bilateria False there are a few Echinodermata who reverted to radial symmetry f All Bilateria have brains False some do centralization has evolved independently many times g All non Bilateria are lacking brains True 2 Suggest an ultimate explanation for why cephalization did not occur until the evolution of bilateral symmetry No definition of an anterior posterior axis or a head region movement is not limited to primarily one direction 3 Suggest an ultimate explanation for why cephalization did not occur on the posterior end Direction of movement for detecting stimuli before they are approached especially visual olfactory auditory near the mouth to assist with feeding and aggressive behaviors 4 List and explain three pieces of evidence that indicate sea squirts phylum Chordata are more closely related to us phylum Chordata than they are to squid phylum Mollusca Deteurostomes vs protostomes mouth and anus are defined like ours during larval embryonic development Presence of notochord CNS precursor Presence of hollow dorsal nerve cord 2 5 In the human motor homunculus below why is the thumb significantly larger than the entire foot it has more motor efferents finer control 6 In the human sensory homunculus below why is the thumb comparable in size to the entire foot same number of sensory afferents