BIOEE 1780 1st Edition Lecture 25Outline of previous lectureI. AnnouncementII. ArthropodsA) General characteristicsB) More on arthropodsIII. Arthropod typesA) MyriopodsB) CrustaceansC) CheliceratesD) InsectsOutline of current lectureI. EchinodermsII. ActivityIII. ChordatesA) CephalochordatesCurrent lectureI. Echinoderms*Common traits among all echinoderms: presence of cilia at some stage of life cycle, radial symmetry, internal skeleton, water vascular system*Video: echinoderms behaving badly-Giant kelp forests the size of a three-story house-Sea urchins prey on the kelp (attacking the holdfasts)-Clear huge areas, called barrens (these are then invades by a number of other organisms, the largest being the huge sunflower sea stars that consume brittle stars)-Sand dollars cluster together as a defense against the sunflower sea star, but to no avail*Synapomorphies of adult echinoderms: pentaradial symmetry (bilateral larvae), water vascular system, tube feet -Tube feet: stick through the skeleton, aid in locomotion and gas/nutrient exchange-Water vascular system: also aids in nutrient/gas exchange-NO HEADS*Groups:1) Sea stars: -Serious predators-Evert stomach to feed-Can be keystone species in marine systems (keystone species mean species with a disproportionally large effect on their ecology in comparison to their biomass)-Suffering waste disease on Pacific coast of US which could have a huge effect on the marine ecology-Can break off arms to evade predators or for asexual reproduction2) Brittle stars-Slender and secretive, often active at night-Scavengers or detritus feeders-Most use arms to swim-Visceral organs in central disk3) Crinoids-Sea lilies, feather stars-Some sessile, some motile, filter feeders-Mouth and anus located on oral surface-Jointed stalk in sessile forms-Arms are food gathering structures-Tube feet coated in mucus-Abundant in ancient seas (3-500 million years ago)4) Sea urchins-Graze on algae, around 950 species-Lack arms, but maintain radial symmetry-Covered in spines (protection and locomotion)-Developed in spines as an extension of their skeleton-Sand dollars-Five teeth5) Sea cucumbers-Around 1700 species -Structurally and physiologically the strangest-Reverted to bilateral symmetry-Elongated in their oral-aboral axis-Oral tentacles around mouth-Move by tube feet and muscle contractions-Only echinoderms to use internal respiratory system-Cuvierian tubules: extraordinary defense mechanism#Expelling guts to protect itselfII. ActivitySponges ctenophores cnidarians chordates echinoderms lophotochozoansecdysozoans Notochord Tube feetBlastophore-mouthIII. Chordates*Synapomorphies: dorsal hollow nerve chord, notochord, segmented post-anal tailA) Cephalochordates-Lancelets-Shallow, marine, suspension filter feeder-Process chordate hallmark features#Notochord:*Resists compression*Allows bending*Like how using our back muscles doesn’t bunch up our whole bodies, but simply bend our