Summary of Deuterostomes and Chordates

  • Deuterostome vs Protostome

    • Protostome:

    • Triploblastic

    • Schizocoelus

    • Can be Coelomate, Acoelomate, or Pseudocoelomate

    • Determinant cell fate

    • Blastopore becomes mouth

    • Deuterostome:

    • Triploblastic

    • Enterocoelus

    • Always coelomate

    • Indeterminate cell fate

    • Blastopore becomes anus

  • Deuterostome Phyla

    • Hemichordata

    • Echinodermata

    • Chordata

    • Focus on Echinodermata and Chordata

  • Phylum Echinodermata

    • Meaning: "spiny skin"

    • Key Features:

    • Secondary pentaradial symmetry

    • Water vascular system with tube feet

    • Capable of regeneration

    • Slow-moving or sessile

    • Calcitic skeleton

  • Class Crinoidea

    • Includes sea lilies and feather stars

    • Sessile and mobile members

    • Filter/suspension feeders

  • Class Echinoidea

    • Includes sea urchins and sand dollars

    • Characterized by 5 teeth ("Aristotle's Lantern")

    • Edible and some have poisonous spines

  • Class Holothuroidea

    • Includes sea cucumbers

    • Reduced endoskeleton, tentacles near mouth

    • Harmful defense mechanism: release poison

  • Class Asteroidea

    • Includes sea stars

    • Possesses regenerative capabilities

    • Predatory behavior using tube feet

  • Class Ophiuroidea

    • Includes brittle and basket stars

    • Long, flexible arms for locomotion

  • Phylum Chordata

    • Bilaterally symmetrical and coelomate

    • Five characteristics:

    • Notochord

    • Dorsal hollow nerve cord

    • Pharyngeal gill slits

    • Post-anal tail

    • Endostyle or thyroid gland

  • Subphylum Cephalochordata

    • Retains all 5 characteristics as adults

  • Subphylum Urochordata

    • Includes tunicates

    • Free-swimming larvae resemble chordates; adults lose most traits

  • Hox Genes

    • Responsible for body structure development

  • Subphylum Vertebrata

    • Contains specialized features like skull and backbone

  • Class Myxini - Hagfish

    • Jawless, no true vertebrae

    • Detritivores with unique defense mechanisms

  • Class Petromyzontida - Lampreys

    • Jawless, parasitic as adults

  • Class Chondrichthyes - Sharks and Rays

    • Cartilaginous skeletons with placoid scales

  • Class Osteichthyes - Bony Fishes and Tetrapods

    • Complete skeletons made of bones

  • Class Amphibia

    • Requires water for reproduction; gas exchange through skin

  • Amniota

    • Adaptations for dry environments; includes reptiles and mammals

  • Class Mammalia

    • Endothermic; produces milk

  • Class Reptilia

    • Best adapted for dry environments, covered with scales

  • Birds

    • Included in Reptilia; adaptations for flight

  • Vertebrate Skull Types

    • Anapsid (no holes) - amphibians & turtles

    • Synapsid (one hole) - mammals

    • Diapsid (two holes) - reptiles and birds