CHAPTER 34 VERTEBRATE EVOLUTION AND DIVERSITY. 1.Notochord (disks) -longitudinal, flexible rod...

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