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Animal Systematics

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									Animal Systematics
          Systematics

• The study of biological diversity and
  classification
• classification of living organisms by
  evolutionary relationship
             Classification

• Carolus Linnaeus (1707-
  1778)
  – Swedish naturalist
• Developed the modern
  taxonomic classification
  system
Linnean System of Classification
 Kingdom     Animalia
 Phylum      Chordata
   Class    Mammalia
  Order      Primates
  Family    Hominidae
  Genus       Gorilla
 Species   Gorilla gorilla
        Revised Linnean System
  Division            Eukarya
 Kingdom             Animalia
  Phylum             Chordata
Subphylum           Vertebrata
 Superclass          Tetrapoda
    Class           Mammalia
  Subclass             Theria
 Infraclass           Eutheria
   Order             Primates
Superfamily       Anthropoidea
   Family           Hominidae
 Subfamily           Ponginae
   Genus              Gorilla
  Species         Gorilla gorilla
Subspecies    Gorilla gorilla beringei
        Binomial Nomenclature
• Genus + species
• Examples:
  –   Rana catesbeiana: bull frog
  –   Turdus migratorius: American robin
  –   Homo sapiens: modern human
  –   Mucosa domestica: house fly
• Subspecies sometimes included
  – Gorilla gorilla beringei: mountain gorilla
          What is an Animal
• Eucaryotic
  – cells divided into organelles
• Multicellular
• Heterotrophic
  – do not produce own nutrients
• Lack cell walls
• Tissues linked by proteins (e.g. collagen)
          What is an Animal
• Cells often linked by cell junctions
  – gap, adhesion, tight
• Possess electrogenic cells
  – nerve cells and muscle cells
• Reproduce sexually (diploid)
  – sperm + egg → zygote → blastula → gastrula
    → larva → adult
Major Evolutionary Divergences
       Among Animals
 • Development of Tissues
 • Development of Body
   Plans
 • Development of Body
   Cavities
 • Developmental Origin
   of the Coelom
      Development of Tissues

• Development of aggregations of similar
  cells into patterns and layers
• Parazoa (sponges) – lack tissues
• Eumetazoa – possess tissues
    Development of Body Plans
• Pattern of body and structure
• Number of embryonic cell layers
• Radiata (e.g. jellyfish, hydra)
   – radial symmetry
   – diploblastic (2 germ cell layers)
• Bilatera (everything else)
   – Blateral symmetry
   – Triploblastic (3 germ cell layers)
  Development of Body Cavities
• Acoleomates (flatworms)
   – no body cavities
• Pseudocoelomates (rotifers,
  roundworms)
   – body cavity not surrounded by
     mesoderm (pseudocoelom)
• Coleomates (everything else)
   – body cavity enclosed by
     mesoderm (coelom)
    Developmental Origin of the
            Coelom
•    Coelomates are divided into two gorups
     based upon:
    1. Pattern of cell cleavage during early
       development
    2. When cell developmental fate is determined
    3. How the coelom is formed
    4. How the digestive tract is formed during
       gastrulation
                      Protostomes
• Mollusks, earthworms, insects, etc.
• Spiral cleavage
   – cell division diagonal to vertical axis
• Determinant cleavage
   – development into tissues determined
     very early in cleavage
• Schizocoelous
   – coelom forms by splitting solid masses
     of mesoderm in
• Blastopore forms mouth
                    Deuterostomes
• Starfish, vertebrates
• radial cleavage
   – cell division at right angles to vertical
     axis
• indeterminant cleavage
   – development into tissues determined
     later in cleavage
• enterocoelous
   – coelom forms by mesoderm layer
     budding from archenteron
• blastopore forms anus
                   Parazoa:
                Phylum Porifera
•   sponges
•   little cell differentiation
•   sessile
•   no nerve or muscle cells
•   porous body
    – enables water circulation
      through the body
    – flow driven by choanocytes
    – food collected and digested
      by amoebocytes
                Radiata:
            Phylum Cnidaria
• Corals, jellyfish,
  anemones, corals
• gastrovascular cavity
  – central compartment
    with single opening
• two basic body plans:
  – polyp – usually sessile
  – medusa – motile form
                Radiata:
            Phylum Cnidaria
• tentacles arranged around
  opening to the
  gastrovascular cavity
• lined with nematocysts
  – stinging cells
• possess nerve cells
  forming nerve net
  – no central nervous system
• possess muscle-like cells
               Radiata:
          Phylum Ctenophora
• Comb jellies
• Similar in appearance to
  jellyfish
• Possess comb-like plates
  of cilia used for
  locomotion
• Collect food with tentacles
  covered with colloblasts
  (lasso cells)
             Acoelomates:
        Phylum Platyhelminthes
• Flatworms
• gastrovascular cavity with one
  opening
• true muscle tissue
• primitive excretory system (water
  balance)
• sensory organs in head
  (photoreceptors, chemoreceptors)
• central nervous system (ganglia in
  head w/ ventral nerve cords)
           Acoelomates:
      Phylum Platyhelminthes
• Major Classes
  – Turbellaria
     • planarians (free living)
  – Monogenea and
    Tremotoda
     • flukes (parasites)
  – Cestoidea
     • tapeworms (parasites)
          Pseudocoelomates:
           Phylum Rotifera
• Rotifers
• complete digestive tract
  – separate mouth and anus
• pseudocoelomic fluid
  acts as circulatory
  system
• cilia lining crown draw
  water into the mouth
           Pseudocoelomates:
               Nematoda
• Nematodes (roundworms)
• complete digestive tract
• pseudocoelomic fluid acts
  as circulatory system
• longitudinal muscle
  orientation
• aquatic habitats, soils,
  plant and animal parasites
       Protostome Coelomates:
          Phylum Nemertea
• Proboscis worms
• acoelomous body, except
  for fluid-filled sac used to
  extend proboscis
• similar excretory, sensory
  and nervous systems to
  flatworms
• complete digestive tract
• closed circulatory system
  (blood confined to vessels)
      Protostome Coelomates:
        Lophophorate Phyla
• possess lophophore
  – ciliated fold around
    mouth
• no head
• U-shaped digestive
  tract
      Protostome Coelomates:
        Lophophorate Phyla
• Bryozoans
  – sessile, resemble
    moss, hard
    exoskeletons
• Phoronids
  – horseshoe worms
• Brachiopods
  – resemble bivalves
      Protostome Coelomates:
         Phylum Mollusca
• Mollusks
• Major Classes:
  – Class Polyplacophora
     • chitons
  – Class Gastropoda
     • snails and slugs
  – Class Bilvalvia
     • clams, oysters, mussels, etc.
  – Class Cephalopoda
     • octopus, squid, nautiluses
        Protostome Coelomates:
           Phylum Mollusca
• Muscular foot
• visceral mass
   – contains organs
• gills (respiration)
• complete digestive tract w/
  specialized organs
• open circulatory system
  (blood not confined to
  vessels)
• mantle
   – covers visceral mass, secretes
     shell
        Protostome Coelomates:
           Phylum Annelida
• Annelids (segmented worms)
• hydrostatic skeleton
• coelom in repeating segments
  with alternating longitudinal and
  circular muscles, setae, and
  metanephridia (excretion)
• closed circulatory system
• several specialized regions in
  digestive tract
• cerebral ganglia with ventral
  nerve cord
     Protostome Coelomates:
        Phylum Annelida
• Major Classes
  – Class Oligochaeta
    (earthworms)
  – Class Polychaeta
    (polychaetes)
  – Class Hirudinea
    (leeches)
        Protostome Coelomates:
          Phylum Arthropoda
• specialization of body
  segments
   – specialized limbs, etc.
• hard exoskeleton
   – protein and chitin
• high cephalization of
  sensory organs
• open circulatory systems
   – blood (hemolymph) not
     confined to vessels
                    Arthropods:
                    Chelicerates
• claw-like feeding appendages
  (chelicerae), lack antennae
• Class Arachnida (spiders,
  scorpions, ticks, mites)
   – 2 body segments (cepahlothorax
     and abdomen)
   – 6 pairs of appendages
      • chelicerae, pedipalps, 4 pr walking
        legs extend from cephalothorax
   – book lungs
      • enhances gas exchange btw
        hemolymph and air
                     Arthropods:
                     Uniramians
• jaw-like feeding appendages
  (mandibles), 1 pair of antennae,
  unbranched appendages
• Class Diplopoda – millipedes
• Class Chilopoda – centipedes
• Class Insecta – insects
   – three body segments (head, thorax,
     abdomen)
   – many possess wings
   – specialized digestive system
   – Malpighian tubules (excretion)
   – tracheal system (respiration)
                   Arthropods:
                   Crustaceans
• mandibles, 2 pair of antennae,
  branched appendages
• Class Crustacea
   – possess gills
   – salt glands (hemolymph salt
     balance)
• Groups
   – Isopods (e.g. pill bugs)
   – Copepods (e.g. Cyclops)
   – Decapods (crabs, lobsters, etc.)
     Deuterostome Coelomates :
      Phylum Echinodermata
• sea stars, sea urchins, sea
  cucumbers
• adults have radial
  symmetry
   – bilateral larvae
• endoskeleton of hard
  plates
• water vascular system
   – used to manipulate tube
     feet
     Deuterostome Coelomates :
         Phylum Chordata
•   Lancelets tunicates, vertebrates
•   Characteristics of embryos:
    1. possess notochord
       •   longitudinal, flexible rod between
           digestive tract and nerve cord
    2. possess dorsal hollow nerve
       cord
    3. have pharyngeal slits
       •   modified for gas exchanges, jaw
           support, hearing, etc.
    4. have muscular postanal tail
       Invertebrate Chordates
• Subphylum Urochordata
  – tunicates
  – sessile marine animals
  – chordate characters seen
    only in larvae
• Subphylum
  Cephalochordata
  – lancelets
         Subphylum Vertebrata
• Characteristics
   – neural crest formation during embryonic
     development
   – vertebral column + skull
   – pronounced cephalization of sensory and
     neural apparati
   – closed circulatory system
• Agnathans
   – lack hinged jaws, notochord present
     throughout life
• Gnathostomes
   – possess hinged jaws, notochord replaced by
     vertebrae, paired appendages
• Tetrapods
   – Possess two pairs of appendages
          Superclass Agnatha


• lack hinged jaws,
• notochord present
  throughout life
• no paired appendages
• lampreys and hagfish
       Superclass Gnathostoma:
             Jawed Fish
• Class Chondrichthyes
   – Sharks, rays
   – cartilaginous skeletons
• Class Osteichthyes
   – bony fish (bone skeletons)
   – Subclass Actinopterygii
      • Ray-finned fish
   – Subclass Sarcopterygii
      • Lobe-finned fish
          Superclass Tetrapoda:
            Class Amphibia
• Characteristics
   – tetrapods (4 limbs)- terrestrial
     movement
   – aquatic larval stage
   – moist, permeable skin
• Anurans
   – frogs and toads
• Urodeles
   – salamanders and newts
• Caecilians
   – legless, fossorial amphibians
          Superclass Tetrapoda:
            Class (?) Reptilia
• Reptiles
• Scaly, impermeable skin
• Amniotes
   – Lay shelled amniotic eggs
• Chelonians (Testudines)
   – Turtles
• Lepidosaurians
   – Tuatara, snakes, lizards
• Archosaurs
   – Crocodilians, dinosaurs, birds
          Superclass Tetrapoda:
               Class Aves
•   Birds
•   Amniotes
•   Possess feathers
•   Possess wings (flight)
•   Endothermic
    – most body heat generated
      internally
• Two-circuit circulatory
  system
       Superclass Tetrapoda:
         Class Mammalia
• Mammals
• Possess hair
• Possess mammary glands
• Endothermic
• Two-circuit circulatory system
• Most give birth to young
  (amniotic)
• Diaphragm for active
  ventilation of lungs
       Superclass Tetrapoda:
         Class Mammalia
• Groups
  – Monotremes
     • lay eggs
     • platypuses, echidnas
  – Marsupials
     • embryo completes development in
       pouch
     • kangaroos and opossums
  – Eutherians
     • form placenta
     • cats, humans, squirrels

								
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