CHAPTER 34VERTEBRATE EVOLUTION
AND DIVERSITY
1. Notochord (disks)-longitudinal, flexible rod between digestive tube and nerve cord-large, fluid filled cells/ stiff fibrous tissue-support-most vertebrates – only remains as “disks”
2. Dorsal, Hollow Nerve Cord
Phylum Chordata Deuterostomes
-develops from ectoderm that rolls into a tube/ dorsally from notochord-develops into the Central nervous system: the brain and spinal cord
3. Pharyngeal Slits
-region of digestive tract posterior to mouth “ “pharynx”/ pouches-filter food for invertebrate chordates-modified for gas exchange (in aquatic vertebrates), jaw support, hearing, and other functions
4. Muscular, Postanal Tail
Some Invertebrates
Subphylum Urochordata (Tunicates/ Sea Squirt) Sessile or Planktonic
Tunic (cellulose-like carbohydrate)
Larva
Subphylum Cephalochordata (Lancelet)“Idealized” chordatesSmall (few cm long)Live in the sand Suspension feeders
Swim like fish Gas exchange mainly across regions of the external body surface
Subphylum VertebrataLarger sizeActive lifestyle
Neural crest (form skeletal elements/braincase)Pronounced cephalizationVertebral columnClosed circulatory system
Endoskeleton Axial skeleton (cranium, vertebrae, ribs) Appendicular skeleton (support appendages) Living/ Grows
Ventral, chambered heart (blood, arteries, capillaries)
Gills or lungs
*Adaptations for feeding, digestion, and nutrient absorption
Jaws/ 2 sets of paired appendages
4 footedshelled, water-retaining egg
Dorsal, hollowNerve cord
Contribute to formationof certain skeletal elements(cranium/ vertebral column)
AgnathansJawless vertebrateseel-like in shape
predate the origin of paired fins, teeth, and bones hardened by mineralization (ossification)
Class Myxini: HagfishesMost primitive living "vertebrates"
Bottom-dwelling scavengersSlime producing glands
Cartilage (connective tissue)
Serpentine swimming
Class Cephalaspidomorphi:Lampreys
larvae for years in freshwater streams migrate to the sea/lakes streams (anadromous)
Cartilaginous pipe surrounding the rodlike notochord
Toothlike structures (keratin)
JawsPaired finsTailActive predators
Gnathostomes Jaws evolved by modification of the skeletal rods that had previously supported the anterior pharyngeal (gill) slits
remaining gill slits = respiratory gas exchange
YouTube - Evolution Of Jaws 1of5YouTube - Evolution Of Jaws 2of5YouTube - Evolution Of Jaws 3of5YouTube - Evolution Of Jaws 4of5YouTube - Evolution Of Jaws 5of5
Class Chondrichthyes: Sharks and raysCartilaginous skeletons Sharp Bony teethStreamlined bodiesPowerful swimming musclesBuoyancy by storing a large amount of oil in its huge liver Animal is still denser than water, and it sinks if it stops swimming
Use muscles of the jaws and pharynx to pump water over the gillsSuspension feeders and CarnivoresShort digestive tract (spiral valve)Acute senses (predation)Sight good (no color)Smell (nostrils)Lateral line system (detect water pressure changesDetect electrical fields generated by muscle contractions of animalsEntire body transmits sound to hearing organs of inner ear (no eardrum)
Internal fertilization (cloaca/ male claspers near pelvic fin)Oviparous; they lay eggs that hatch outside the mother’s body. Ovoviviparous; they retain the fertilized eggs in the oviduct. Viviparous; the young develop within the uterus, nourished by placenta
Class Osteichthyes: The bony fishesRay-finned fishes, lobe-finned fishes, and the lungfishes
Most numerous vertebratesOssified endoskeleton (calcium phosphate)Flattened, bony scalesMucous glandsLateral line systemFour or five pairs of gillsOperculum (muscle movement)Swim bladderFlexible finsMost oviparous
Ray-finned fishes Bass, trout, perch, tuna, herring, etc. Fins supported by long flexible rays
Lobe-finned fishes Coelacanth Muscular pectoral and pelvic fins supported by extensions of the bony skeleton
Lungfishes Lungs connected to the pharynx of the digestive tract Gills (main organs for gas exchange) Aestivate (state of torpor).
Tetrapods
Tetrapod Evolution
Coelacanth
Adaptations to shallow waterBuccal pumping/ mouth breathing (lungfishes and frogs)Leglike appendagesAcanthostega
Tetrapods
Class AmphibiaSalamanders, frogs, and caecilians
Moist skin to carry out gas exchangeEggs lack a shell (dehydrate)External fertilization (most)Complex and diverse social behaviorRapid and alarming population decline (worldwide)
Order Urodela "tailed ones"Salamanders
Aquatic and Terrestrial (as adults)Walk with a side-to-side bending swagger (resembling early tetrapods)
Order Anura "tail-less ones"Powerful hind legsLong sticky tongueCamouflageSkin glands (distasteful/poison mucus) Brightly colored (poisonous)Metamorphosis
Amniotes reptiles, birds, and mammals
Adaptations to land (terrestrial)Amniotic egg (shell)Extra embryonic membranesWaterproof skinIncreasing use of the rib cage to ventilate the lungs
key differences between the three groups in their skull anatomy
Scales (protein keratin)LungsShelled amniotic eggs (land/ leather)Internal fertilizationViviparous (some lizards and snakes)“Cold blooded”Ectothermic (basking)Dominant terrestrial vertebrates for +200 million yearsDinosaurs and Pterosaurs Social behavior and parental care Endothermic?
Class: Reptilia (lizards, snakes, turtles, crocodiles)
Order Testudines (turtles) Order Squamata (lizards and snakes)
Order Crocodilia (alligators and crocodiles)
Hard shellLay eggs on land
LizardsMost numerous and diverse reptilesRelatively small
SnakesDescendants of lizards that adapted to a burrowing lifestyle (vestigial limbs)LimblessCarnivorousAcute chemical sensorsLack eardrums but sensitive to ground vibrationsHeat-detecting organs between the eyes and nostrils of pit vipersToxin through a pair of sharp hollow or grooved teethTongue (olfactory organs on the roof of the mouth)Loosely articulated jaws
Among the largest living reptilesUpturned nostrils
Order Testudines (turtles)
Class: Reptilia (lizards, snakes, turtles, crocodiles)
Order Squamata (lizards and snakes)
Order Crocodilia (alligators and crocodiles)
Class: Aves (birds)
Amniotic eggs and scales on the legs (reptilian features)Flight Bones are honeycombed (light) Absence of some organs (one ovary) Toothless Gizzard grinds food (crocodiles/dinosaurs) Beak of keratin (adaptations)Active metabolism Endothermic Feathers (retain heat) Advanced circulatory (4 chambered heart) Advanced respiratoryAcute senses Sight (possibly the best) Motor skills/ coordinationSocial behaviorInternal fertilization
Large pectoral (breast) muscles anchored to a keel on the sternum (breastbone)Feathers (endothermy and flight)
Archaeopteryx
Ratites (no keel)Carinates (keels)
Passeriformes“perching”
Class: MammaliaMammary glandsHair (keratin)EndothermicCirculatory-4 chambered heartRespiratory-diaphragmFat (retain heat)
Internal fertilizationBirth (some placenta)Large brainsCognitive abilitiesExtended parental care
Differentiation of dentition (teeth)Inner ear (from jaw bones)
Therapsids
Monotremes (platypuses spiny anteaters) Egg laying (reptilian like) Milk and hair No nipples (just glands)
Marsupials (Opossums, kangaroos, koalas) Early birth Pouch (marsupium) Austraila
Eutherians (Placental) Longer gestation (pregnancy)
Spiny Anteater
Platypus
Order: PrimatesGrasping handsOpposable thumb (big toe)Larger brainFlattened faceStereoscopic visionNailsFinger skin ridges (prints)Extended parental careComplex social behaviorCoordinationFlexible joints
Prosimians
New WorldMonkeys Old World
Monkeys
Lemurs
TarsierBushbaby
Great Apes/ HumansHominoids
Bonobo chimpanzee
Gorilla Chimpanzee
Orangutan
Australopithecines
Homo habilis Homo erectus Homo sapiens
~5 – 2 mya
~2 – 1.5 mya ~1.6 mya ~400,000 – 100,000 ya
Hominids
BipedalismLarger brain (~400 cm3 1300 cm3)Shorter jawsDentitionSexual dimorphism (male size to female)Extended parental careFamily structureLearning
“Lucy”
~5 million years of Evolution
Pan troglodytes Homo sapiens
HumanDiversity
Homo sapiens