Amvulacraria Cephalochorda ta and Tunicata Lab Lab 21922 Amvulacraria Cephalochordata and Tunicata Lab Lab 21922 Representatives of Enteropneusta and Petrobranchia Collar Feeding Tentacles Trunk Proboscis Proboscis Trunk Enteropneusta ptychopterid Petrobranchia cephalodiscidae Representatives of Enteropneusta and Petrobranchia 8 2 Question 1 What characteristics inform us that hemichordates have a phylogenetic affinity i e share a common ancestor with to Echinodermata and Chordata Deuterostome development all 3 groups belong to the deuterostome clade Bilateral larvae all have bilateral larval stages in their life cycles Fossil evidence fossils provide insight into the evolutionary history of these groups Some homologous characteristics Pharyngeal gill slits dorsal nerve cord endostyle and homologous structures 8 2 Question 1 What characteristics inform us that hemichordates have a phylogenetic affinity i e share a common ancestor with to Echinodermata and Chordata Deuterostome development all 3 groups belong to the deuterostome clade Bilateral larvae all have bilateral larval stages in their life cycles Fossil evidence fossils provide insight into the evolutionary history of these groups Some homologous characteristics Pharyngeal gill slits dorsal nerve cord endostyle and homologous structures Echinodermata pedicellariae tube feet pyloric stomach ring canal cardiac stomach dermal papillae Spine ampullae gonads anus endoskeleton radial canal ambulacral groove madreporite Echinodermata Sea Star Development As the sea star larva progresses through these stages it undergoes significant changes in body shape and structure transitioning from the bipinnaria s bilateral symmetry to the brachiolaria s more compact and arm bearing form Sea Star Development 8 4 Questions and Summary 1 How do we know that starfish should be grouped with other bilaterians instead of with the radially symmetrical group Cnidaria or biracially symmetrical group Ctenophora Echinoderms like starfish are grouped with other bilaterians based on embryological development genetic evidence and shared characteristics during larval stages 2 Why don t echinoderms have a circulatory system homologous to other groups for distributing gasses and nutrients throughout the body Echinoderms use a water vascular system for gas exchange and nutrient distribution obviating the need for a conventional circulatory system 3 Speculate on the adaptive significance of the planktonic larvae phase seen in echinoderms Planktonic larvae in echinoderms aid in dispersal feeding predator avoidance and increasing genetic diversity enhancing their chances of survival and reproduction in marine Summary Asteroidea sea stars radially symmetrical with five arms and a central disc Ophiuroidea brittle stars slender arms distinct from the central disc Echinoidea sea urchin spherical or flattened bodies with a rigid endoskeleton 8 4 Questions and Summary 1 How do we know that starfish should be grouped with other bilaterians instead of with the radially symmetrical group Cnidaria or biracially symmetrical group Ctenophora Echinoderms like starfish are grouped with other bilaterians based on embryological development genetic evidence and shared characteristics during larval stages 2 Why don t echinoderms have a circulatory system homologous to other groups for distributing gasses and nutrients throughout the body Echinoderms use a water vascular system for gas exchange and nutrient distribution obviating the need for a conventional circulatory system 3 Speculate on the adaptive significance of the planktonic larvae phase seen in echinoderms Planktonic larvae in echinoderms aid in dispersal feeding predator avoidance and increasing genetic diversity enhancing their chances of survival and reproduction in marine environments Amphioxus Whole Mount Structures Amphioxus Whole Mount Structures Amphioxus Cross Section Structures Amphioxus Cross Section Structures Adult Tunicate Structures Branchial incurrent siphon Mout hTuni c Endostyle Pharyngeal Basket Atrium Anus Intestine Stigmat a slits Genital Ducts Stomach Adult Tunicate Structures Larvae Tunicate Structures Statocyst Ocelius Adhesive papillae Nerve cord Larvae Tunicate Structures 8 4 Questions 1 Both Cephalochordates and Tunicate individuals are very small Forma hypothesis that explains their size and absence of any known large forms These animals have retained a primitive filter feeding lifestyle Their small size may be an adaption for efficient filter feeding in aquatic environments 2 Which chordate characteristics were you able to identify in the adult A couple of characteristics I noticed was a notochord a dorsal hollow nerve cord and pharyngeal gill slits 3 What are the four main derived characters that unite all the chordates into a monophyletic group The four main derived characters are the notochord post anal tail pharyngeal gill slits and dorsal nerve cord 4 What is the primary feeding structure used by tunicates and cephalochordates The primary feeding structure used by tunicates and cephalochordates is the pharynx 5 If adult tunicates are less complex that adult cephalochordates why do most scientists accept the hypothesis that tunicates are more closely related to the more complex vertebrates while Cephalochordata forms the base of the chordate tree The hypothesis that tunicates are more closely related to vertebrates while cephalochordates form the base of the chordate tree is based on molecular and genetic evidence 8 4 Questions 1 Both Cephalochordates and Tunicate individuals are very small Forma hypothesis that explains their size and absence of any known large forms These animals have retained a primitive filter feeding lifestyle Their small size may be an adaption for efficient filter feeding in aquatic environments 2 Which chordate characteristics were you able to identify in the adult A couple of characteristics I noticed was a notochord a dorsal hollow nerve cord and pharyngeal gill slits 3 What are the four main derived characters that unite all the chordates into a monophyletic group The four main derived characters are the notochord post anal tail pharyngeal gill slits and dorsal nerve cord 4 What is the primary feeding structure used by tunicates and cephalochordates The primary feeding structure used by tunicates and cephalochordates is the pharynx 5 If adult tunicates are less complex that adult cephalochordates why do most scientists accept the hypothesis that tunicates are