Animal diversity and relationshipsLiving formsSlide 3Slide 4Slide 5Slide 6Slide 7Slide 8Slide 9Slide 10Slide 11Slide 12The fossil recordSlide 14Slide 15Slide 16Slide 17Slide 18Slide 19Slide 20Slide 21Slide 22Slide 23Slide 24How to make sense out of diversity without fossils.Slide 26Slide 27Slide 28Slide 29Slide 30Slide 31Slide 32Slide 33Slide 34Slide 35Slide 36Slide 37Now what?Protostomes vs deuterostomesSlide 40Protostomes – how to organizeSlide 42Slide 43Slide 44Slide 45Slide 46New phylogenySlide 48Slide 49Slide 50Slide 51Slide 52Slide 53Animal diversity and relationshipsLiving forms•At least 30 phyla•But only x “important” ones Importance = numerous, ecologically important, and fit into our conceptions of evolutionPorifera = spongesAssymetrical, 2 cell layers , internal silica spicules = skeleton.Cnideria, jellyfish, coralsRadially symmetrical, 2 cell layers, one ended digestive system. Often with algae inside to provide nourishmentLight sensitivity.Ctenophora – comb jelliesBilateral, one ended gut, marinePlatyhelminthes = flat worms. Three cell layers, no body cavity, one ended digestive system, brain, nerves, many are parasitic.Two ended digestive systemHead and tail, have an internal cavity – not solid.Very numerous in soil.Annelida = segmented worms; bigger most free living. Have nerves, three cell layers, true body cavity = coelom, circulatory system, excretory system. Skin breathing and many have legs. Some carnivorous, soil eaters or leaches – blood suckersMollusca: clams, snails, squid, octopus, slugsTwo ended gut, nerves, circulation, filter feeders or carnivorous. Some (squid, octopus) with eyes, brain, etc. Remnants of segmentation – chitins.Arthropods – joint leg = insects, crustaceaSegmented, brain, sense organs, excretory systemEchinoderms – pentaradiate,Starfish, urchins, sea lillys.Chordata, including vertebrata . Backboned organisms.The fossil recordHow to determine relationships – try fossils first.Burgess Shale in British Columbia, a unique preservation at the right age.Segmented worms (with legs?)arthropodsChordate – similar to early members of this groupsponge????Result of fossil record: all major groups plus some other odd ones appear almost simultaneously = no sequental appearance.How to make sense out of diversitywithout fossils.Rules: simple to complex symmetry (assymetrical, radial, bilateral)Cell layers – 1 to 2 to 3Embryology - (old ontogeny recapitulates phylogeny statement of Haeckel)Digestive system design; one ended to two endedErnst Haeckel, 1866; “ontogeny recapitulates phylogeny” = early stages of development mirror evolutionary changes.Note – gill clefts in all embryos, tail present, etc.Basis; development is often incremental – add new stages to old – harder to change the beginning stages.Classic example of this, the aortic arches in vertebrates.Start with a complete set; need gill arches to deposit them.All embryos have gill clefts and a complete set of archesTo get to adult stages, loose some of the arches.Phylum porifera; sponges. assymetricalBecause of assymetry, doesn’t fit into any neat story – so viewed as a development separate from everything else.Symmetry, bilateral or radialJellyfish, corals, radialcnideriaRadial symmetry plus one ended digestive system = primitiveBilateral symmetry; all other groups.Clues from development1. Hollow ball of cells2. Then 2 cell layers, one opening,radial symmetry= cnidaria3. Then three cell layers – new opening bilateral symmetry = all higher formsCell layers 2 vs 3. sponges and cnideria = 2Digestive system – one ended vs. two endedFlatworms – bilaterial but with one openning to digestive systemOther ‘worms’ – two ended digestive system.So: 1 – no symmetry, followed by radial and then bilateral - porifera oldest then cnidaria, then everything else 2. one ended gut, followed by 2 ended. 3. 2 cell layers, followed by threeNow what?Use embryology – the great Protostome – Deuterostome splitProtostomes vs deuterostomes•First opening = mouth•Determinate clevage•Spiral clevage•Mesoderm = 4d cell•Schizocoel coelom•First opening = anus•Indeterminate clevage•Radial clevage•Mesoderm = infolding•Endocoel coelomProtostomes – how to organize•Classical method mesoderm – solid to pseudocoelom to true coelom one ended gut to two ended no segments to segmentsBody cavity (coelom) in relation to mesoderm Solid mesoderm = no coelom = flatworms acoelomateCoelom partially lined with mesoderm = roundworms pseudocoeleCoelom completely lines with mesoderm = Segmented worms, vertebrates, etc. true coelomResult = Flatworms – one opening dig system, solid (acoelomate)Round worms; two openings dig system pseudocoelSeg. Worms (annelids) segments true coelomArthropods – trilobite = segmented and legsMolluscs = chitin, segmented. Odd –legs??Trilobite = arthropodaChitin = molluscaMarine worm = annelidaAll segmented.Deuterostome, protostome splitProtostomes groups by segmentation.Link segmentation togetherNote: Classical classification((it’s wrong))New phylogeny•Lophotrochozoans•Filter feeders•Ecdysozoans•Shell sheddersTwo phylogenies: left based on hypothesized relationships, right based on Both genetic similarity and time. Right is correct in that all major groups appear almost simultaneously (brushpile evolution)Note: flatworms,mollusc and annelid together// no arthropodsArthropods and round worms in this group.Central position of flatworms as ancestral.Question marks. separateEcdysozoansShell shedderssegmentedNEXTHow come the old phylogeny wrong?1. Segmentation arose more than once – not a unifying trait2. Some organisms, especially parasites (flatworms, roundworms) may have gotten simpler in structure through time.3. A poor choice of “unifying”