Exercise Echinoderms - Chordates Worksheet

Echinodermata & Chordata Phylum Echinodermata: The name Echinodermata translates to “Spiny Skin”. This is because the skin of Echinoderms contains calcareous ossicles, giving them a flexible yet tough covering. Echinoderms are also known for their unique water vascular system (see diagram on Moodle) which allows for locomotion, feeding, sensory reception, and gas exchange. This system is composed of the madreporite, stone canal, ring canal, radial canals and Polian vesicles/ampullae. The madreporite allows water to enter and exit this system (on sea stars, it can be seen as the small round plate on the top). The stone canal is a calcareous tube connecting the madreporite and the ring canal. The ring canal encircles the gut/center of the organism and can be thought of as a “splitter” connecting each arm’s “pipes”, or radial canals, to the central stone canal. The Polian vesicles/ampullae contract and expand to create the water pressure that controls the tube feet. Use the Slides and Specimens and Lecture Powerpoints to answer the following questions. 1) Observe the water vascular system shown in the YouTube video in the link above. Describe the path of the flow of water through the sea star. The components of the water vascular system of echinoderms are madreporite, stone canal, circular ring canal, radial canals, lateral canals, and tube feet. Sea stars or echinodermatas allow the water to flow through their body with the help of the water vascular system. The water enters the body through the madreporite which is then circulated by the stone canal to the ring canal and ultimately to the radial canals. The function of the radial canal is to transport the water to the ampulla and then helps the water absorbed to initiate suction to the tube feet. 2) Looking at the images of echinoderm specimens, what type of symmetry do you see with these organisms? How does the positioning of the madreporite affect symmetry? Echinoderms are exclusively marine invertebrates which have a distinct and peculiar water vascular system which is called ambulacral system. Madreporite is a calcareous opening through which water enters into water vascular system. Echinoderms have bilateral symmetry in their larval stage and radial symmetry in adult stage. In the first figure which refers to sea cucumber which has madreporite inside the body and it has radial symmetry. In the second figure which refers to sand dollar which has madreporite on top surface and it has both radial and bilateral body symmetry. In the third figure which refers to sea urchin which has madreporite on central disk on the aboral surface (away from mouth) which shows radial symmetry during adult stage and bilateral symmetry during larva stage. 3) What types of defense are found in various Echinoderms? There are different types of defense mechanisms which are exhibited by Echinoderms. They include spiny skin, expulsion of internal organs, regenerative abilities, thick cell walls, and calcium deposition under skin. 4) Use the slides and specimens PowerPoint to observe and draw each of the following classes: Class Holothuroidea (sea cucumbers), Class Crinoidea (feather stars and Crinoids), Class Asteroidea (sea stars), Class Ophiuroidea (brittle stars and basket stars), Class Echinoidea (sand dollars and sea urchins). Be sure to label and describe their characteristic features (see lecture ppt)!! 5) Do organisms in phylum Echinodermata appear to be benthic (living at the bottom of the water) or pelagic (living in the water column between the surface and the bottom)? Why? Organisms in phylum Echinodermata are mostly benthic (living at the bottom of the ocean). There is only one organicism that is a pelagic called Pelagothuria. Since most echinoderms are benthic, the larvae are usually planktonic with bilateral symmetry and will change its body shape from bilaterally symmetrical to radically symmetrical during the process of maturing. Phylum Chordata: Characteristics of chordates (present at some stage of development): Notochord, pharyngeal slits/pouches, dorsal hollow nerve cord, post-anal tail. (See lecture ppt). Terminology: Notochord - a flexible rod made out of a material similar to cartilage. If a species has a notochord, it is, by definition, a chordate. The notochord develops into the vertebral column in some groups. Dorsal Hollow Nerve Chord - a hollow cord dorsal to the notochord. The dorsal nerve cord is later modified in vertebrates into the central nervous system which is composed of the brain and spinal cord. Pharyngeal Slits/Pouches- function in filter-feeding and gas exchange in some primitive chordates. In others, they develop into structures such as the inner ear and various glands. Post-anal tail- A tail that extends past the anus. Cephalization - the concentration of sense organs, nervous control, etc., at the anterior end of the body, forming a head and brain. Integument - the natural covering of an organism or an organ, such as its skin, husk, shell, or rind. The word is derived from integumentum, which means "a covering" in Latin. Transitional Groups: These groups represent the evolutionary steps leading to vertebrates. Although the adults may not resemble typical vertebrate animals, these organisms possess all four characteristic chordate traits at some point in their life cycle. The transitional groups are entirely marine. Phylum Hemichordata - Short dorsal nerve chord, gill slits. (Acorn-worms) Subphylum Urochordata - Larvae display full array of vertebrate characteristics, many of which are lost by the adult stage. (Tunicates) Subphylum Cephalochordata - Display cephalization, dorsal nerve chord throughout entire life. (Lancelets) 6) Observe and draw the Lancelet Amphioxus slide. Remember this specimen is a chordate so it has all 4 of the chordate features. Be sure to label each of these. Subphylum Vertebrata: Class Myxini (Hagfishes) - Bottom-dwelling marine scavengers. Jawless fishes. Class Cephalaspidomorphi (lampreys)- Blood-sucking marine parasites. Possess primitive vertebrae. Jawless fishes. Class Chondrichthyes (sharks, skates, rays) - skeleton of mineralized cartilage. Small, tooth-like scales. First animals to evolve jaws, which can be quite complex and ferocious in some species. Unlike many bony fishes, Chondrichthyes often give birth to live young. Gestation periods can last for over a year, making these species incredibly vulnerable to extinction. Superclass Osteichthyes - (Bony Fishes) Largest, most diverse of all the Chordates. Mineralized skeleton (bones). Ectothermic: control their body heat through external sources. Well-developed nervous system including a “lateral line” to detect vibrations (think of schooling fish). Class Amphibia (Frogs, salamanders, caecilians) - Moist, glandular integument without scales; used for cutaneous respiration. Limbs adapted for terrestrial life, with digits. Require water for larval stage. Class Reptilia (snakes, lizards, turtles, crocodilians, and birds) - Water-tight amniotic egg. Internal fertilization. Tough, dry, scaly integument. Well-developed lungs. Dominant animals during the Mesozoic. Class Mammalia (mammals) - The most recently evolved chordate class. Most mammals have lost the amniotic egg, and instead have placental development. Other characteristics include long gestation periods, mammary glands, and hair. Approximately 5,000 species. 7) Draw a specimen of each of the groups in the subphylum Vertebrata listed above (use the slides and specimens ppt). Be sure to label and describe the adaptation of each group that separates it from the previous group. (Hintinclude form/function/habitat in your descriptions).