ORG EVO UNO GRADE CUTIE

• Chordates


  Bilaterian animals that belong to the clade of animals known as Deuterostomia
• Chordates


  • Vertebrates
  • Urochordates
  • Cephalochordates
• Derived characters of chordates

  • Notochord
  • Dorsal, hollow nerve cord
  • Muscular, post-anal tail
  • Pharyngeal slits or clefts
• Notochord


  A longitudinal, flexible rod between the digestive tube and nerve cord that provides skeletal support
• Dorsal, hollow nerve cord

  Develops from a plate of ectoderm that rolls into a tube dorsal to the notochord, develops into the central nervous system
• Muscular, post-anal tail


  Contains skeletal elements and muscles, provides propelling force in many aquatic species
• Pharyngeal slits or clefts


  Grooves in the pharynx that develop into slits that open to the outside of the body, have various functions in different chordates
• Lancelets (Cephalochordata)


  • Marine suspension feeders that retain characteristics of the chordate body plan as adults, larvae feed on plankton

  
• Tunicates (Urochordata)


  • Resemble chordates during their larval stage, as adults draw in water through an incurrent siphon to filter food particles
• Ancestral chordates may have resembled lancelets
• Craniates


  Chordates that have a head, enabling more complex movement and feeding behaviors
• Derived characters of craniates

  • Two clusters of Hox genes (lancelets and tunicates have only one)
  • Neural crest, a collection of cells near the dorsal margins of the closing neural tube that give rise to various structures
• Vertebrates


  Craniates that have a backbone
• Derived characters of vertebrates

  • Vertebrae enclosing a spinal cord
  • Elaborate skull
  • Fin rays in aquatic forms
• Lampreys (Petromyzontida)


  • Jawless vertebrates that feed by clamping their mouth onto a live fish, have a cartilaginous skeleton

  
• Conodonts were the first vertebrates with mineralized skeletal elements in their mouth and pharynx

  
• Mineralization appears to have originated with vertebrate mouthparts, and was an adaptation that allowed animals to become scavengers and predators
• Gnathostomes


  Vertebrates that have jaws, which might have evolved from skeletal supports of the pharyngeal slits

  
• Other characters common to gnathostomes

  • Genome duplication, including duplication of Hox genes
  • Enlarged forebrain associated with enhanced smell and vision
  • Lateral line system sensitive to vibrations (in aquatic gnathostomes)
• Chondrichthyans (Sharks, Rays, and Their Relatives)


  • Have a skeleton composed primarily of cartilage, include some of the biggest and most successful vertebrate predators in the ocean
• Shark reproduction


  Eggs can be fertilized internally and develop in different ways: oviparous, ovoviviparous, or viviparous
• The reproductive tract, excretory system, and digestive tract of sharks empty into a common cloaca
• Osteichthyans


  The vast majority of vertebrates, including bony fish and tetrapods, have a bony endoskeleton
• Oviparous


  Eggs hatch outside the mother's body
• Ovoviviparous


  The embryo develops within the uterus and is nourished by the egg yolk
• Viviparous


  The embryo develops within the uterus and is nourished through a yolk sac placenta from the mother's blood
• The reproductive tract, excretory system, and digestive tract empty into a common cloaca
• Osteichthyes


  A clade of gnathostomes, the vast majority of vertebrates
• Nearly all living osteichthyans have a bony endoskeleton
• Osteichthyans includes the bony fish and tetrapods
• Aquatic osteichthyans are the vertebrates we informally call fishes
• Fishes


  • Breathe by drawing water over gills protected by an operculum
  • Control their buoyancy with an air sac known as a swim bladder
  • Have a lateral line system
  • Most species are oviparous, but some have internal fertilization and birthing
• One of the most significant events in vertebrate history was when the fins of some lobe-fins evolved into the limbs and feet of tetrapods
• Derived characters of tetrapods

  • Four limbs, and feet with digits
  • A neck, which allows separate movement of the head
  • Fusion of the pelvic girdle to the backbone
  • The absence of gills (except some aquatic species)
  • Ears for detecting airborne sounds
• Tiktaalik


  A "fishapod" showing both fish and tetrapod characteristics

  
• Amphibians (class Amphibia) are represented by about 6,150 species
• Urodela


  Order of amphibians including salamanders, which have tails
• Amphibian


  Means "both ways of life," referring to the metamorphosis of an aquatic larva into a terrestrial adult
• Most amphibians have moist skin that complements the lungs in gas exchange
• Fertilization is external in most amphibian species, and the eggs require a moist environment