What is an animal?

What is an animal? •  Mul.cellular heterotrophs: feed by inges&on. •  How does this differ from plants, fungi, pro.sts? What is an animal? •  Carbohydrates stored as glycogen •  Polysaccharide of glucose •  (no, you do not need to know this structure) What is an animal? •  No cell walls •  Cells supported by structural proteins: collagen –  Extracellular matrix, supports .ssues, gives cells structure from outside –  Triple-‐helix structural protein What is an animal? •  Nerve and muscle .ssue •  Impulse & movement What is an animal? •  Generally, most have sexual reproduc.on from anisogamous or heterogamous gametes. What is an animal? • 
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Development Egg + Sperm ⇒ Zygote ⇒cleavage ⇒ Blastula ⇒ Gastrula ⇒ Larva or juvenile ⇒ Adult •  This development regulated by Hox genes Animal Diversity •  The vast majority of animal species are marine •  Only truly terrestrial* animals come from 5 phyla – 
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Mollusca Annelida Onychophora Arthropoda Chordata •  *Does not include internal parasites nor taxa needing constant external moisture Animal Origins •  Monophyle&c •  Sister taxon Choanoflagellates (pro.st protozoan) •  Colonial, flagellated pro.st ancestor Animal Origins •  Gastrula-‐like infolding into two layers •  Increased specializa.on of cells and .ssues beginning with soma&c vs reproduc&ve Animal Origins •  Molecular evidence: –  Suggests divergence from fungi ~1 bya –  Common ancestor of animals 675-‐875 mya Animal Origins •  Fossil evidence: –  Possible trace fossils ~900 mya –  Ediacaran fauna 610-‐550 mya •  Animals??? –  Definite animal fossils (about 1/2 of phyla) appear during Cambrian Explosion. Animal Origins The Cambrian Explosion •  Why so sudden? 1.  Predator-‐Prey interac.ons and coevolu.onary arms races. 2.  Increase in atmospheric oxygen allows for larger animals with higher metabolic rates. 3.  Key innova&on of Hox genes allows rapid diversifica.on of developmental pathways. Morphological Trends Symmetry •  Radial vs bilateral •  Radial –  Top and bofom only-‐-‐
no leg or right –  Likely ancestral trait: Cnidarians, Ctenophores Morphological Trends Symmetry •  Radial vs bilateral •  Bilateral –  Top-‐bofom, forward-‐
backward, leg-‐right –  Allowed cephaliza&on, more ac.ve lifestyle. Morphological Trends Tissues •  Porifera or Parazoa (sponges) lack true .ssues (this is a unique development) Gastrula.on •  Germ layers are formed by the process of gastrula&on •  One end of blastula folds inward, eventually produces layers of embryonic .ssue Gastrula.on •  Blastula is a mul.-‐
cellular embryonic stage that is typically a hollow ball of cells that surrounds a cavity called a blastocoel Gastrula.on •  The invagina.on or gastrula.on results in the gastrula stage •  The pouch formed is called the archenteron and the opening to the outside is called the blastopore Gastrula.on •  Animals with only ectoderm and endoderm have only gastrula.on as germ layer forma.on •  Cnidaria (jellies) and Ctenophora (comb jellies) •  Diploblas&c Gastrula.on •  All bilateral animals have a third germ layer, the mesoderm •  Forms muscles and most organs between diges.ve tract and the outer covering. •  Triploblas&c Body Cavity: The Coelom •  Most triploblas.c animals have a body cavity –  Fluid-‐ or air-‐filled space separa.ng the diges.ve tract from the outer body wall. •  This is the coelom Body Cavity: The Coelom •  The coelom forms from .ssue derived from mesoderm •  COELOMATES: –  Mesoderm connects dorsally and ventrally and provides a complete lining of the coelom Body Cavity: The Coelom •  The coelom forms from .ssue derived from mesoderm •  PSEUDO-‐
COELOMATES: –  Coelom is lined with mesoderm (outside) and endoderm (inside) Body Cavity: The Coelom •  The coelom forms from .ssue derived from mesoderm •  ACOELOMATES: –  No true body cavity –  Ogen sog-‐bodied organisms. Body Cavity: The Coelom •  All three groups (Coelomates, Pseudocoelomates, and Acoelomates) are polyphyle&c. •  Body cavity (coelom) also coincides with complete diges.ve tract (mouth, anus) and circulatory system (vessels or sinuses) Coelomates: Protostomes & Deuterostomes • 
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Classic division in Bilateria Differences Pafern of early cell division To&potency in early cell development The forma.on of the coelom Fate of the blastopore Coelomates: Protostomes & Deuterostomes Protostomes •  Early cell division is via spiral cleavage Deuterostomes •  Early cell division is via radial cleavage Coelomates: Protostomes & Deuterostomes Protostomes •  Fate of cells is determined at early cleavage stages: Determinate cleavage Deuterostomes •  Cells at early cleavage stages remain to&potent: Indeterminate cleavage Coelomates: Protostomes & Deuterostomes Protostomes •  Solid mass of mesoderm splits to form coelom: schizocoelous Deuterostomes •  Coelom forms from mesodermal outpocke.ngs of the archenteron: enterocoelous Coelomates: Protostomes & Deuterostomes Protostomes •  Blastopore becomes mouth Deuterostomes •  Blastopore becomes anus General Classifica.on of Animalia •  Currently considerable debate on rela.onships between animal phyla. •  Remember, Animalia is monophyle.c. General Classifica.on of Animalia •  Sponges branch first, form the Porifera or Parazoa. –  Morphology and molecules disagree about monophyly –  Generally considered paraphyle.c –  Animalia without true .ssues •  Everything else form Eumetazoa –  Animalia with true .ssues General Classifica.on of Animalia •  Radiata are paraphyle.c: Cnidaria & Ctenophora –  Radial symmetry –  Diploblas.c •  Bilateria are monophyle.c –  Bilateral symmetry –  Triploblas.c General Classifica.on of Animalia •  Bilateria divided into four groups: –  Acoela –  Deuterostomia •  Echinodermata •  Chordata –  Ecdysozoa •  Nematoda •  Arthropoda –  Lophotrochozoa • 
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Platyhelminthes Ro.fera Ectoprocta Brachiopoda Mollusca

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