INTRODUCTION TO ANIMAL EVOLUTION

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CHAPTER 32

• INTRODUCTION TO ANIMAL EVOLUTION

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• ANIMALS
• OVER 1 MILLION SPECIES
• 95 ARE INVERTEBRATES
• GROUPED INTO ABOUT 35 PHYLA
• MOST ARE AQUATIC
• MOST FAMILIAR PHYLUM CHORDATA
• SUBPHYLUM VERTEBRATA

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• WHAT IS AN ANIMAL?
• MULTICELLULAR, HETEROTROPHIC EUKARYOTIC ORGANISMS
• NO CELL WALLS
• HELD TOGETHER BY COLLAGEN
• UNIQUE INTERCELLULAR JUNCTIONS
• DESMOSOMES
• GAP JUNCTIONS
• TIGHT JUNCTIONS

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• ANIMALS (cont)
• NERVE TISSUE FOR IMPULSE CONDUCTION
• MUSCLE FOR LOCOMOTION
• REPRODUCTION USUALLY SEXUAL
• SPERM FLAGELLATED
• EGG NON-MOTILE
• DIPLOID STAGE DOMINATES THE LIFE CYCLE
• LARVAE FREE LIVING SEXUALLY IMMATURE FORMS
• METAMORPHASIS CHANGE INTO SEXUALLY MATURE ADULTS

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• PARAZOANS (PORIFERA)
• SPONGES
• SIMPLE ANATOMY
• LACK TRUE TISSUES

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• EUMATOZA
• TRUE TISSUE ANIMALS 2 BRANCHES
• RADIATA
• BILATERIA

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• RADIATA
• RADIAL SYMMETRY
• ORAL TOP
• ABORAL BOTTOM
• NO FRONT, BACK, LEFT OR RIGHT
• ARRANGED LIKE SPOKES OF A WHEEL
• ANY SLICE THROUGH THE CENTRAL AXIS WOULD DIVIDE
  THE ANIMAL INTO A MIRROR IMAGE
• PHYUM
• CNIDERIA JELLYFISH, CORAL, ANEMONES
• CTENOPHORA COMB JELLIES

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• BILATERIA
• BILATERAL SYMMETRY
• DISTINCT BODY REGIONS
• EXHIBIT CEPHALIZATION
• ECHINODERMATA (SEA URCHIN) EXCEPTION

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• GERM LAYERS
• ECTODERM COVER THE EMBRYO SURFACE, WILL FORM
  THE OUTER COVERING AND NERVE SYSTEM
• ENDODERM INNERMOST LAYER, LINES THE ARCHENTERON
  (PRIMITIVE GUT) FORMS THE DIGESTIVE TRACT LINING,
  LIVER AND LUNGS
• MESODERM FOUND IN BETWEEN THE 2 LAYERS. FORMS
  MUSCLE AND CONNECTIVE TISSUE

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• GASTRULATION
• RADIATA DEVELOP TWO GERM LAYERS. KNOWN AS
  ECTODERM AND ENDODERM. DIPLOBLASTIC
• BILATERIA DEVELOP 3 GERM LAYERS. ECTO, ENDO
  AND MESODERM. TRIPLOBLASTIC

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• BODY CAVITY EVOLUTION
• ACOELOMATE NO BODY CAVITY, platyhelminthes (no
  blood-vascular system)
• PSEUDOCOELOMATE BODY CAVITY IS ONLY PARTIALLY
  LINED WITH MESODERMAL TISSUE nematodes (blood
  vascular system)
• COELOMATES TRUE COELOM. BODY CAVITY IS
  COMPLETELY LINED WITH MESODERMAL CELLS. CREATES
  A FLUID FILLED BODY CAVITY (blood vascular system)

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• FUNCTION OF FLUID FILLED CAVITY
• CUSHION ORGANS
• ALLOW INTERNAL ORGANS TO GROW AND MOVE
  INDEPENDENT OF BODY WALLS
• SERVES AS A HYDROSTATIC SKELETON IN SOFT BODIED
  COELOMATES (ANNELIDS)

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• COELOMATE PHYLA
• 2 DISTINCT EVOLUTIONARY LINES
• PROTOSTOMES MOLLUSKS, ANNELIDS AND ARTHROPODS
• DEUTEROSTOMES ECHINODERMS AND CHORDATES

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• CLEAVAGE
• PROTOSTOMES
• SPIRAL CLEAVAGE PLANES OF CELL DIVISION ARE
  DIAGONAL TO THE VERTICAL AXIS OF THE BODY
• DETERMINATE CLEAVAGE THE FATE OF EACH CELL IS
  ESTABLISHED VERY EARLY IN DEVELOPMENT

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• CLEAVAGE
• DEUTEROSTOMES
• RADIAL CLEAVAGE CLEAVAGE PLANES ARE EITHER
  PARALLEL OR PERPENDICULAR TO THE VERTICAL AXIS OF
  THE EMBRYO
• INDETERMINATE CLEAVAGE EARLY EMBRYONIC CELLS
  RETAIN THE CAPACITY TO DEVELOP INTO A COMPLETE
  EMBRYO IS ISOLATED FROM OTHER CELLS (HUMANS THE
  RESULT IS IDENTICAL TWINS)

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• BLASTOPORE
• THE FIRST OPENING IN THE ARCHENTERON WHICH WILL
  FORM DURING GASTRULATION
• PROTOSTOMES FORMS THE MOUTH
• DEUTERSTOMES FORMS THE ANUS

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• COELOM
• PROTOSTOME SCHIZOCOELUS AN INITIAL SOLID MASS
  OF MESODERM WHICH SPLITS TO FORM THE COELOM
  CAVITY
• DEUTERSTOME ENTEROCOELUS COELOM DEVELOPS AS
  MESODERM AND ARISES AS A LATERAL OUTPOCKETING OF
  THE ARCHENETERON WHICH HOLLOWS AND BECOMES THE
  COELOM CAVITY

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Various animals that developed during the
Cambrian explosion