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P10- Lecture 22- Animals II

P10- Lecture 22- Animals II - Animals II Chordates Lecture...

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Unformatted text preview: Animals II: Chordates Lecture 22 Two Great Branches of Bilaterian Tree s Protostomes x Lophotrochozoa 3 E.g. 3 E.g. Annelids Arthropods x Ecdysozoa s Deuterostomes x E.g. Chordates Two Great Branches of Bilaterian Tree s Deuterostomes x Echinoderms x Chordates x Why together? 4 Chordate Characteristics s Notochord Unity of Plan x Structural support s Dorsal Hollow nerve cord x Elsewhere ventral 33.5b s Pharyngeal slits x Feeding, then breathing s Muscular Tail x Propulsion Chordates and Activity Level s From ancestors with a relatively low metabolic rate, chordates evolve a highly active lifestyle!! s Parallels among the Protostomes Vertebrate Origins Urochordata = tunicates Cephalochordata = Amphioxus Vertebrata ? Invertebrate Chordates s Tunicates 3 Most (or sea squirts) are sessile as adults 3 All marine suspension feeders s Like vertebrates x Segmented x Can be fast Amphioxus Our baseline for vertebrates s But, lack x Well-developed brain x Heart x Gills/lungs x Neural crest cells s And is small Vertebrate Origins s Neural crest cells x Develop from ectoderm Vertebrate Origins s Neural crest cells x Form or contribute to many very important structures: 3 E.g. See 34.10 Sense organs 3 Skull to protect brain 3 Parts of nervous system 3 Gill arches - Feeding and breathing Vertebrates s Great sense organs x Eyes, nose, hearing s Jointed skeleton x Vertebral column x (Arthropods too!) s Extreme cephalization s Closed circulatory system Vertebrate Origins Urochordata Cephalochordata Vertebrates Neural Crest , heart , brain, skelet on, great sense organs Not ochord, Dorsal Hollow nerve cord, Pharyngeal slit s, muscular t ail Vertebrate Relationships Gnathostomata Tetrapoda "Agnatha" "Fishes" Amphibians Amniotes Amniot ic egg Joint ed limbs Jaws s "Agnatha" x No Jaws Vertebrate Relationships See 34.10 s Gnathostomata x Jaws 3 Evolve from gill arches (NCC) 3 More effective feeding 3 Supports higher metabolism Jawless vertebrates s 2 Agnathans: x Hagfish 3 Most primitive living vertebrates parasites x Lampreys 3 Predatory s Extremely successful in water xWide range of habitats xNo major invasions of land Jaws: Sharks and bony fishes xMost vertebrates are bony fishes xDevonian period- "Age of fishes" Chondrichthyes: Sharks and Rays xCartilaginous fish Osteichthyes: Bony fishes s Characteristics: x Ossified skeleton x Gills covered by operculum x Swim bladder s 3 classes: x Ray-finned fishes x Lobe-finned fishes x Lungfishes 3 Gills and lungs Tetrapoda s Amphibians, Reptiles, Birds, and Mammals s Very successful on land s Jointed appendages x More effective movement s Amphibians still rely on water for reproduction x "Age of amphibians" 3 Carboniferous period of Paleozoic era Class Amphibia sAmphibians: xSalamanders xFrogs xCaecilians s Eggs lack shell & must stay moist Vertebrate Relationships Gnathostomata Tetrapoda "Agnatha" "Fishes" Amphibians Amniotes Amniot ic egg Joint ed limbs Jaws Look at Figure 34.7 s Much more successful on Amniotes land than amphibians x Reptiles x Birds x Mammals s Have dry scaly skin to reduce water loss (remember the plant cuticle?) Amniotes s Amniotic egg s What was equivalent for land plants? Amniotic egg x Protection of embryo from environment 3 Amnion x Storage of wastes 3 Allantois x Gas exchange 3 Chorion x Yolk sac 3 nourishment 34.16 Relationships among Amniotes "Reptiles" Birds Mammals Common Amniote ancestor = reptile-like Reptiles s Paraphyletic groups x Some closer to birds (e.g. croc) or mammals than to other reptiles s Dominated land for a very long time x Overshadowed mammals for 140 million years! x Mesozoic era "Age of reptiles" 3 ~240 to 140 million years ago Extant Reptiles s Tuataras s Turtles s Lizards and snakes s Alligators and crocodiles Birds and Mammals Independently evolved a high metabolic rate! s High body temperature x Insulation - feathers or fur s Very efficient locomotion s Very efficient respiration s Four chamber heart x Complete separation of high/low oxygen blood Birds and Mammals Independently evolved a high metabolic rate! s Feathered reptiles x Mesozoic era Birds x Have scales on legs s Theropod ancestors s Archaeopteryx intermediate in many ways extinct side branch to birds: x Teeth, claws, tail s Flight x Feathers Birds x Honeycombed bones x Wings s Complex courtship x Brooding Mammals s Arose about 220 mya x Cenozoic era "Age of mammals" s Primitively, laid eggs x Two species still do! 3 Platypus, echidna s Derived similarities include: x Hair x Lactation x Three-bone middle ear s Monotremes x Egg-laying 3 Major groups of Mammals s Marsupials x Pouches s Eutherian x placental Proposed cladogram of mammals Summary s Chordates are Deuterostomes s Trend towards high energy lifestyle s Chordate characteristics x Notochord, Dorsal hollow nerve cord, Pharyngeal slits, tail s Vertebrates have Neural crest cells, skeleton x Important for high energy lifestyle s Gnathostomes have jaws x More efficient feeding Summary - continued s Tetrapods have jointed limbs x Better locomotion on land s Amniotes have an amniotic egg x More resistant to drying s Birds and mammals have independently evolved many features related to a very high metabolic rate x Effective respiration, circulation, locomotion, high body temperature, insulation Hominidae - Our Twig of the Tree s What does it mean to be human? s What makes us distinctive? s Think about this : x Where would you draw the line between human and non-human? ...
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