Animals Lab Practical #2

• Phylum Echinodermata


  • Class Holothuroidea (sea cucumbers, look like slugs)
  • Class Ophiuroidea (brittle stars)
  • Class Crinoidea (feather stars)
  • Class Echinoidea (urchins, sand dollars)
  • Class Asteroidea (sea stars)
• Echinoderms


  • Deuterostomes and have radial indeterminate cleavage
  • Either radially symmetrical or pentaradially symmetrical and are unsegmented
  • Feature that gives the phylum its name is a dermal skeleton that is often spiny and is composed of calcareous ossicles or spicules
  • Skeleton is covered by a layer of epidermis
• Digestive system of echinoderms

  1. Mouth, found on the oral side

  2. Short esophagus

  3. One or two part stomach

  4. Digestive glands

  5. Anus
• Water vascular system


  Derived from the coelom, provides locomotion, excretion, respiration, and food gathering functions, opens to the outside through a madreporite and projects from the body surface as tentacle-like projections
• Gas exchange in echinoderms

  • Via dermal branchia (skin gills) through the tube feet, or by a "respiratory tree" in the Holothuroidea
• Echinoderms have no heart and a much reduced vascular system
• Echinoderms have a reproductive system consisting of large gonads with simple ducts, the sexes are usually separate, and they have external fertilization
• Sea Star External Anatomy

  • Pentaradial symmetry: five arms projecting from the center disc
  • Dermal branchia: thin walled tissue
  • Pedicellaria: tiny pincer-like appendages located at the base of the spines
  • Madreporite: functions as the entrance to the water vascular system
  • Ambulacral groove: groove running down the center of each arm, enclosed by ambulacral ossicles
• Ecology of Echinoderms


  • Entirely marine group, cannot osmoregulate, never found in brackish water, bottom dwellers
• Class Holothuroidea


  • Elongated and their ossicles are much reduced and buried in a leathery dermal layer, generally crawl along the bottom, but are capable of burrowing and swimming
• Class Ophiuroidea


  • Brittle stars generally prefer the deeper ocean areas, and many species are negatively phototropic, use their arms to filter suspended particles or browse on the bottom
• Class Crinoidea


  • Sessile filter feeders that live attached to the substrate, use their long tentacles to gather suspended food particles
• Class Echinoidea


  • Includes sea urchins, sand dollars and heart urchins, have an elaborate chewing system known as Aristotle's Lantern composed of a complex set of muscles that control the movements of five teeth used for grazing
• Class Asteroidea


  • Sea stars, prey on molluscs, crustaceans and many other invertebrates, feed on oysters and clams by prying open the shell slightly with their arms and extruding their stomach into the shell, where digestion takes place
• Vertebrate Evolutionary Patterns


  • P. Hemichordata- acorn worms
  • P Chordata
  • S.P. Urochordata- tunicates and sea squirts
  • S.P. Cephalochordata- Lancelets
  • S.P. Verterata
  • Class Myxini- Hagfish
  • Class Petromyzontida- Lampreys
  • Class Chondrichthyes- Sharks, rays, skates
  • Super class osteichthyes- bony fish
  • Class Amphibia
  • Order Gymnophiona- Caecilians
  • Order Anura- Frogs
  • Order Caudata- Salamanders, newts
  • Class Reptilia
  • Order Testudines- Terrapins, tortoises, turtles
  • Order Squamata- Snakes, Lizards
  • Order Crocodulia- Alligators, Crocodiles
  • Class Aves
  • Order Anseriformes- Waterfowl
  • Order Galliformes- Landfowl
  • Order Falconiformes- Diurnal flesh eating birds
  • Order Columbiformes- Doves, Pigeons
  • Order Cuculiformes- Cuckoos
  • Order strigiformes- Owls
  • Order Piciformes- Woodpeckers and relatives
  • Order Passeriformes- Perching birds
• The chordates are a relatively diverse group of organisms that have succeeded in almost every environment on the planet