2 Phylum ArthropodaSeveral million species.Hard exoskeleton.
3 Phylum Arthropoda: Arthropods (crustaceans, spiders, insects) Hard exoskeleton, segmented bodies, jointed appendagesArthropods are the most successful of all animal phyla based on diversity, distribution, and numbers.Nearly one million species identified so far, mostly insects.The exoskeleton, or cuticle, is composed of protein and chitin.Molting of the cuticle is called ecdysis.Extensive cephalization.Open circulatory systems in which a heart pumps hemolymph through short arteries and into open spaces (sinuses).Aquatic members- gills for gas exchange; terrestrial members- tracheal system of branched tubes leading from surface throughout body.
5 Four evolutionary arthropod lineages a. Trilobites – extinctb. Chelicerates – horseshoe crabs, spidersc. Uniramians – centipedes, millipedes, insectsd. Crustaceans – crabs, lobsters, barnacles From these lineages arose five major classes of arthropods.
12 Echinoderm Classes Riley Galton Asteroidea – Sea Stars: Multiple arms radiating from central diskTube feet on bottomOphiuroidea – Brittle Stars:Distinct central disk with snake like armsTube feet lack suckers
13 Echinoderm Classes Riley Galton Echinoidea – Sea Urchins and Sand Dollars:No arms, but 5 rows of tube feetHave muscles that can movespinesCrinoidea – Feather Stars and Sea LiliesFlexible arms used in suspension feedingHaven’t changed in 500 million years
14 Echinoderm Classes Riley Galton Holothuroidea – Sea Cucumbers Reduced endoskeletonFive rows of tube feetConcentricycloidea – Sea DaisiesOnly two known speciesDisk shaped, less than 1cm in diameter
15 Echinoderm Sensory Structures Riley GaltonEchinoderm Sensory StructuresEyespots on the ends of ambulacra are sensitive to lightPedicellariae (jaw like skeletal structures used to keep organisms from settling on skin), tube feet, and spines are sensitive to touch
16 Body Symmetry Julia Heunis evolved from animals with bilateral symmetryadult echinoderms possess radial symmetryAll echinoderms exhibit fivefold radial symmetry in portions of their body at some stage of life (5 parts around central axis), even if they have secondary bilateral symmetryFor the most part…LARVAE ~ bilateralADULTS ~ radial
17 Skeletal Type Echinodermata: “Spiny Skinned” Julia HeunisSkeletal Type Echinodermata: “Spiny Skinned”DO NOT possess an exoskeletona thin outermost skin covers a mesodermal endoskeleton made of tiny calcified plates and spines - forms rigid support contained within tissues of the organismSkeleton composed of skeletal plates called ossiclesOssicles = small bonesIn some species, such as the sea urchin, plates of the skeleton are locked together to form a rigid structure.most sea stars and brittle stars can flex their ‘arms’ = skeleton has gaps, flexible plate junctures
18 Other Unique Features Julia Heunis Echinoderms can REGENERATE ex: sea cucumbers can eject a portion of gut in response to predators and regenerate when safeWater vascular system (described earlier) is unique to echinoderms; varies water pressure to control tube feetCrinoids and some brittle stars = passive filter-feeders, absorbing suspended particles from passing watersea urchins = grazerssea cucumbers = deposit feedersstarfish = active hunters
19 More Unique Features Julia Heunis Autonomy = The spontaneous self amputation of an appendage when the organism is injured or under attack. The autotomized part is usually regenerated.“arms” → multiples of 5; some have more because of regenerationmutable collagenous tissue ~ connect ossicles; can maintain different positions without much effort
20 Locomotion/Musculature David LinLocomotion/MusculatureUtilize water vascular system and tube feetWater in from madreporite, pumped into ampulla by radial canalAmpulla contracts, water to podiaPodia contracts, water to ampullaPodia bend, shorten allows movement (vacuum and suction)
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