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Chapter 40: Echinoderms and chordates Copyright 2005 McGraw-Hill Australia Pty Ltd PPTs t/a Biology: An Australian focus 3e by Knox, Ladiges, Evans and Saint 40-1 Deuterostomes • • During embryonic development, blastopore becomes anus Phylum Echinodermata – sea stars, sea cucumbers, sea urchins • Phylum Chordata – acorn worms, sea squirts, lancelets, vertebrates Copyright 2005 McGraw-Hill Australia Pty Ltd PPTs t/a Biology: An Australian focus 3e by Knox, Ladiges, Evans and Saint 40-2 Fig. 40.1: Deuterostome phylogeny Copyright 2005 McGraw-Hill Australia Pty Ltd PPTs t/a Biology: An Australian focus 3e by Knox, Ladiges, Evans and Saint 40-3 Echinoderms • • • Sea stars, sea cucumbers, sea urchins, sea lilies, brittle stars Pentameric symmetry in adults Characteristics – calcareous endoskeleton – bilaterally symmetrical larvae – water vascular system Copyright 2005 McGraw-Hill Australia Pty Ltd PPTs t/a Biology: An Australian focus 3e by Knox, Ladiges, Evans and Saint 40-4 Classification • Class Crinoidea (sea lilies, feather stars) • Class Asteroidea (sea stars) • Class Concentricycloidea (sea daisies) • Class Ophiuroidea (brittle stars) • Class Echinoidea (sea urchins, heart urchins, sand dollars) • Class Holothuroidea (sea cucumbers) Copyright 2005 McGraw-Hill Australia Pty Ltd PPTs t/a Biology: An Australian focus 3e by Knox, Ladiges, Evans and Saint 40-5 Anatomy • Endoskeleton – calcite (CaCO3) spicules or ossicles embedded in integument • Larva – free-swimming, bilaterally symmetrical – pentameric symmetry develops at metamorphosis • Water vascular system – coelomic canals – gas exchange and locomotion Copyright 2005 McGraw-Hill Australia Pty Ltd PPTs t/a Biology: An Australian focus 3e by Knox, Ladiges, Evans and Saint 40-6 Water vascular system • • • Water enters through sieve-like madreporite Stone canal → ring canal → radial canals Stone canal – calcified tube, connects madreporite to ring canal • Ring canal – runs around base of arms • Radial canals – run along arms; tube feet and ampullae for locomotion Copyright 2005 McGraw-Hill Australia Pty Ltd PPTs t/a Biology: An Australian focus 3e by Knox, Ladiges, Evans and Saint 40-7 Fig. 40.3: Structure of a sea star Copyright 2005 McGraw-Hill Australia Pty Ltd PPTs t/a Biology: An Australian focus 3e by Knox, Ladiges, Evans and Saint 40-8 Chordates • Acorn worms, sea squirts, lancelets, vertebrates • Bilateral symmetry • Characteristics – notochord – pharyngeal slits – dorsal hollow nerve cord • Oldest fossils from Cambrian (530 million years ago) Copyright 2005 McGraw-Hill Australia Pty Ltd PPTs t/a Biology: An Australian focus 3e by Knox, Ladiges, Evans and Saint 40-9 Classification • Subphylum Hemichordata (acorn worms, pterobranchs) • • • Subphylum Urochordata (sea squirts, tunicates) Subphylum Cephalochordata (lancelets) Subphylum Craniata (fish, amphibians, reptiles, birds, mammals) Copyright 2005 McGraw-Hill Australia Pty Ltd PPTs t/a Biology: An Australian focus 3e by Knox, Ladiges, Evans and Saint 40-10 Anatomy • • Characteristics of chordates are present at some stage of the life cycle Notochord – dorsal rod between nerve cord and gut, attachment point for blocks of muscles (myotomes) • Pharyngeal slits – paired openings in pharynx, used for filter feeding in some chordates • Dorsal nerve cord – hollow nerve cord above notochord, expanded anteriorly to form brain in some chordates Copyright 2005 McGraw-Hill Australia Pty Ltd PPTs t/a Biology: An Australian focus 3e by Knox, Ladiges, Evans and Saint 40-11 Subphylum Hemichordata • Acorn worms, pterobranchs • Characteristics – – – – • tripartite body: proboscis, collar, trunk pharyngeal slits filter food particles from water mouth in groove between proboscis and collar dorsal nerve cord in collar Marine, solitary (acorn worms) or colonial (pterobranchs) Copyright 2005 McGraw-Hill Australia Pty Ltd PPTs t/a Biology: An Australian focus 3e by Knox, Ladiges, Evans and Saint 40-12 Subphylum Urochordata • Sea squirts, tunicates, salps • Characteristics – notochord and dorsal nerve cord in pelagic forms (larvae and adults) – incurrent and excurrent siphon for water intake and expulsion – pharyngeal slits filter food particles from water – adult body encased in tunic composed of tunicin (form of cellulose) • Marine, solitary or colonial, sessile or pelagic Copyright 2005 McGraw-Hill Australia Pty Ltd PPTs t/a Biology: An Australian focus 3e by Knox, Ladiges, Evans and Saint 40-13 Subphylum Cephalochordata • Lancelets • Characteristics – – – – – • notochord extends for full length of body muscle blocks (myotomes) along body pharyngeal slits filter food particles from water oral hood with buccal cirri around mouth dorsal and tail fins, paired metapleural folds Marine, solitary, benthic Copyright 2005 McGraw-Hill Australia Pty Ltd PPTs t/a Biology: An Australian focus 3e by Knox, Ladiges, Evans and Saint 40-14 Subphylum Craniata • Jawless fish and vertebrates – oldest fossil craniates are lower Cambrian (530 million years ago) • Characteristics – head with cranium (skull) of cartilage or bone – brain with cranial nerves • Marine, freshwater or terrestrial, solitary, mobile Copyright 2005 McGraw-Hill Australia Pty Ltd PPTs t/a Biology: An Australian focus 3e by Knox, Ladiges, Evans and Saint 40-15 Agnatha • • Lampreys and hagfish Characteristics – cartilaginous skeleton – notochord persists in adults – lack jaws • • Extinct jawless fish were bottom-dwelling filter or detritus feeders Modern jawless fish are blood-feeding ectoparasites or scavengers Copyright 2005 McGraw-Hill Australia Pty Ltd PPTs t/a Biology: An Australian focus 3e by Knox, Ladiges, Evans and Saint 40-16 Gnathostomata • • Vertebrates (fish, amphibians, birds, reptiles and mammals) Characteristics – vertebrae replace notochord in adult – projections from vertebrae protect nerve cord and aorta – neural crest cells give rise to many structures in the head and other parts of the body – dentine and enamel often form teeth or denticles • Evolution of jaws from gill-arches allowed vertebrates to exploit a range of diets Copyright 2005 McGraw-Hill Australia Pty Ltd PPTs t/a Biology: An Australian focus 3e by Knox, Ladiges, Evans and Saint 40-17 Fig. 40.13: Evolution of jaws Copyright 2005 McGraw-Hill Australia Pty Ltd PPTs t/a Biology: An Australian focus 3e by Knox, Ladiges, Evans and Saint 40-18 Chondrichthyes • Cartilaginous fish: sharks, rays, skates, chimaeras • Characteristics – – – – • skeleton of cartilage (frequently calcified) fins with broad bases lack swim bladder denticles in skin and along jaws Marine or freshwater (few species), benthic or pelagic Copyright 2005 McGraw-Hill Australia Pty Ltd PPTs t/a Biology: An Australian focus 3e by Knox, Ladiges, Evans and Saint 40-19 Actinopterygii • • Ray-finned fish: sturgeons, paddlefish, barramundi, eels, seahorses, butterflyfish etc. Characteristics – – – – • skeleton of bone fins with narrow bases, supported bony rays swim bladder present jaw formed of teeth-bearing dermal bone Marine or freshwater, benthic or pelagic Copyright 2005 McGraw-Hill Australia Pty Ltd PPTs t/a Biology: An Australian focus 3e by Knox, Ladiges, Evans and Saint 40-20 Sarcopterygii • Lobe-finned fish: coelacanths and lungfish • Characteristics – fins with broad, fleshy bases • Sarcopterygians are the closest relatives of tetrapods (amphibians, sauropsids and mammals) – similarities in pelvic girdle, pectoral and pelvic appendages, dermal bones and heart • Marine or freshwater, benthic or pelagic Copyright 2005 McGraw-Hill Australia Pty Ltd PPTs t/a Biology: An Australian focus 3e by Knox, Ladiges, Evans and Saint 40-21 Amphibia • Frogs, toads, newts, salamanders, caecilians • Characteristics – – – – – • skull with occipital condyles that articulate with vertebrae single sacral vertebra glandular skin without epidermal structures eggs lack shells lungs and skin used in gas exchange Freshwater and terrestrial Copyright 2005 McGraw-Hill Australia Pty Ltd PPTs t/a Biology: An Australian focus 3e by Knox, Ladiges, Evans and Saint 40-22 Amniotes • • Vertebrates (sauropsids, mammals) Characteristics – extra-embryonic amnion encloses embryo in fluid-filled sac – embryonic allantois (outgrowth of hindgut) is used for excretion during development – thick, waterproof skin with scales, hair or feathers – intervertebral disc – atlas and axis are first two cervical vertebrae • Amniotes include Sauropsida (birds, ‘reptiles’) and Mammalia Copyright 2005 McGraw-Hill Australia Pty Ltd PPTs t/a Biology: An Australian focus 3e by Knox, Ladiges, Evans and Saint 40-23 Fig. 40.19: Relationships of amniotes Copyright 2005 McGraw-Hill Australia Pty Ltd PPTs t/a Biology: An Australian focus 3e by Knox, Ladiges, Evans and Saint 40-24 Sauropsida: Chelonia • Turtles, tortoises and terrapins • Characteristics – body protected by dorsal and ventral shields (carapace and plastron respectively) – shoulder (pectoral) girdle lies inside rib cage – skull anapsid (lacks openings to accommodate jaw muscles) – jaws toothless Copyright 2005 McGraw-Hill Australia Pty Ltd PPTs t/a Biology: An Australian focus 3e by Knox, Ladiges, Evans and Saint 40-25 Sauropsida: Lepidosauria • Snakes, lizards and tuatara • Characteristics – teeth fused to edges of jaws – some species can shed tail at pre-formed fracture points (autotomy) – snakes can disarticulate jaws to accommodate large prey • Tuataras (Sphenodon) of New Zealand are ‘living fossils’ – only surviving members of order Rhynchocephalia Copyright 2005 McGraw-Hill Australia Pty Ltd PPTs t/a Biology: An Australian focus 3e by Knox, Ladiges, Evans and Saint 40-26 Sauropsida: Archosauria • Crocodiles, birds, dinosaurs • Characteristics – diapsid skull with additional preorbital opening – moveable membrane over eye – muscular gizzard • Most of the diagnostic characteristics of birds are adaptations to flight – birds are descendants of the dinosaur lineage Copyright 2005 McGraw-Hill Australia Pty Ltd PPTs t/a Biology: An Australian focus 3e by Knox, Ladiges, Evans and Saint 40-27 Mammalia • Characteristics – epidermal hair – milk production from mammary glands – left aortic arch carries systemic circulation • Subclass Prototheria – Order Monotremata (egg-layers) • Subclass Theria – Order Metatheria (marsupials) – Order Eutheria (placentals) Copyright 2005 McGraw-Hill Australia Pty Ltd PPTs t/a Biology: An Australian focus 3e by Knox, Ladiges, Evans and Saint 40-28 Primates • • Lemurs, tarsiers, monkeys, apes (including humans) Characteristics include – prehensile digits and opposable thumb – bicuspid premolars, molars with three to five cusps – binocular vision, large brain • Strepsirhini (lemurs, lorises, galagos, pottos) – rhinarium (nose pad) with slit-like nostrils • Haplorhini (tarsiers, monkeys, apes) – nose with rounded nostrils Copyright 2005 McGraw-Hill Australia Pty Ltd PPTs t/a Biology: An Australian focus 3e by Knox, Ladiges, Evans and Saint 40-29 Fig. 40.30: Phylogeny of primates Copyright 2005 McGraw-Hill Australia Pty Ltd PPTs t/a Biology: An Australian focus 3e by Knox, Ladiges, Evans and Saint 40-30 The first hominids • • Characteristic bipedal gait of hominids frees hands for grasping food, holding young, nest-building and tool-making Sahelanthropus tchadensis (7 to 6 million years ago) – Djurab Desert, Chad, Africa – ape-like brain case, short face and ‘human’ teeth • Australopithecus (4.4 to 2.5 million years ago) – Ethiopia to South Africa – forward-jutting face, brow-ridge, ‘human’ hands and molar teeth Copyright 2005 McGraw-Hill Australia Pty Ltd PPTs t/a Biology: An Australian focus 3e by Knox, Ladiges, Evans and Saint 40-31 Paranthropus • • Tool-making hominids coexisted with Homo in Africa Paranthropus (2.8 to 1.6 million years ago) – skulls with sagittal crests – powerful jaw with large premolars – vegetarian, used digging tools (probably for collecting tubers and other plant material) Copyright 2005 McGraw-Hill Australia Pty Ltd PPTs t/a Biology: An Australian focus 3e by Knox, Ladiges, Evans and Saint 40-32 Homo: increase in brain size • Oldest fossils of Homo are c. 2.5 million years old – H. rudolfensis and H. habilis coexisted with Australopithecus in Africa • Differences between Homo and Australopithecus – brain capacity of Homo larger than Australopithecus – reduction in jaw and tooth size – evidence of tool-making (H. habilis) • More modern species with larger brain capacity – H. ergaster from Africa – H. erectus from Java (‘Java Man’) and China (‘Peking Man’) made more sophisticated tools than H. habilis Copyright 2005 McGraw-Hill Australia Pty Ltd PPTs t/a Biology: An Australian focus 3e by Knox, Ladiges, Evans and Saint 40-33 Origin of Homo sapiens • Competing theories of origin of Homo sapiens • Out-of-Africa theory – migration of anatomically modern humans from Africa, replacing all other populations of Homo – mtDNA evidence suggests a common ancestor 170 000 years ago • Multiregional theory – anatomically modern humans evolved semiindependently from H. erectus-like ancestors simultaneously in different region Copyright 2005 McGraw-Hill Australia Pty Ltd PPTs t/a Biology: An Australian focus 3e by Knox, Ladiges, Evans and Saint 40-34