Animal Diversity: Form and Function

Kingdom Animalia - multicellular aerobic heterotrophs

Ways to organize animal diversity

What is a tissue?

Tissue types

Animal Diversity - The Kingdom Animalia

Phylum Porifera - sponges

Sponges are primarily filter feeders
  • Collar cells with flagella beat, pulling in water and food
  • Influx passes through the matrix, where amoebocytes and collar cells absorb food
  • Structure maintained by spicules

Phylum Cnidaria

Examples: corals, jellyfish, hydra


  • radially symmetrical animals with only two tissue types
    • Endoderm - forms digestive tract
    • Ectoderm - forms epidermis
    • Mesoglea - jelly-like acellular substance between tissues (the "jelly" in jellyfish)
      • Not a true tissue
    • First organisms with a nervous system - not centralized (no brain)
    • Incomplete digestive tract
    • Possess nematocysts - stingers - unique character in group
      • Use to stun food for predaceous types

How do organisms arrange three tissue types?

Phylum Platyhelminthes - the flatworms

Examples: planarians, flukes, tapeworms
  • acoelomate
  • usually internal parasites or free living organisms
  • incomplete digestive tract
  • flatworms are structurally limited by not having a fluid-filled cavity

Phylum Nematoda - the roundworms

  • psuedocoelomate
  • usually internal parasites
  • complete digestive tract (possess both mouth and anus)
  • separate sexes
  • possess lateral muscles - can only move side to side (cannot manipulate coelomic fluid)

nematode anatomy

Phylum Molluska - mollusks

Examples: snails, clams, octopus

Three main classes (there are more, but we will only look at these three):

Class Gastropoda - snails & slugs
  • Usually have a coiled shell
  • Extremely diverse
  • Slugs = terrestrial gastropod which has lost shell

Octapus vulgaris Loligo forbesi Nautilus sp.
Class Cephalopoda - octopus, squid, Nautilus

Class Bivalva - clams, oysters
  • Two shells which can open and close
  • Aquatic

Phylum Annelida - segmented worms

Examples: earthworms, leeches, polychetes
  • coelomate
  • Ventral nerve cord
  • Two types of muscles - longitudinal & circular
  • Full utilization of coelom in movement, support
polychete worm

Phylum Arthropoda - arthropods

Examples: scorpions, spiders, insects

Subphylum Chelicerata - Chelicerates

Examples: scorpions, spiders, horseshoe crabs, ticks

Tarantula sp. Scorpion

Subphylum Mandibulata - Mandibulates

Examples: millipedes, centipedes, lobsters, insects


There are many groups of mandibulates. We will only be looking at two.

hermit crab shrimp

sulfur moth honey bee
cockroach preying mantis

Note: insect images taken from The Virtual Insectary

The Deuterostomes

Phylum Echinodermata

Examples: sea urchins, starfish, sea cucumbers

sea cucumber starfish sea urchin

A tube foot, an extension of the water vascular system of a starfish. The tube feet act like little suction cups which enable to starfish to grasp onto the sediment for movement or to break into bivalves for food. Note that since this is not a muscular system, they will not tire.

Phylum Chordata

Examples: Sea squirts, lancelets, vertebrates

Subphylum Urochordata - the sea squirts
  • larval stage possesses all of the chordate characteristics
  • most of these characteristics are lost when the larvae undergo metamorphosis and emerge as adults
  • adult stage are primarily sessile filter-feeders

Subphylum Cephalochordata - the lancelets
  • possesses all of the chordate characteristics throughout life cycle
  • burrow into sand and use mucous-secreting organs to filter-feed
  • are feeble swimmers

Subphylum Vertebrata

BONE - reduction of notochord (vertebral disks)

lamprey Class Agnatha - the jawless fish (not monophyletic)

Examples: lamprey, hagfish

  • no jaws
  • most are parasitic fish
  • very diverse group in past. Now, only a few species are still hanging on

sand tiger shark

Class Chondrichthyes - the cartilaginous fish (monophyletic ??)

Examples: sharks, rays, skates

Class Osteichthyes - bony fish (not monophyletic)

Examples: marlin, bass, catfish, anglefish, eels

scaley head
sea horse
wolf eel


Class Amphibia - amphibians (not monophyletic)

Examples: frogs, salamanders

  • Living skin - must be moist to breathe
  • Lay eggs in water
  • Outcompeted in water (fish) and land (reptiles)

Class Reptilia - reptiles (not monophyletic)

Examples: lizards, snakes, gators

  • first truly terrestrial animals
  • Amniotic egg
  • Scales (lungs now sole respiratory organ)
  • Modificatons of pectoral and pelvic girdles to facilitate movement on land

Class Aves - birds (monophyletic)

Examples: robin, jays, emu

  • Feathers
  • warm-blooded (high metabolic rate)
  • hollow bones

Class Mammalia - mammals (monophyletic)

Examples: elephant, bats, Al Gore

vampire bat
deer mouse


So, How Does It All Fit Together?

Click here to view a diagram of animal phylogeny

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