Chapter 34

Vertebrate Diversity

Chordate Phylogeny

Phylum ChordataBilaterian deuterostomesDerived characteristics

NotochordIn all embryos and some adults, between digestive tube and

nerve cordProvides skeletal support, reduced in humans to vertebral

discsDorsal hollow nerve cord

Roll of ectoderm that is unique to chordates becomes CNSPharyngeal slits or clefts

Series of pouches along the pharynx that open to the outside of the body

Filter feeding in invertebrates and gas exchange in vertebratesMuscular, post-anal tail

Reduced in many speciesPropels many aquatic species

Subphylum CephalochordataLancelets have a

bladelike shapeRetain all 4

characteristics of chordates as adults

Filter feedersGas exchange across

bodyMuscles for movement

in and out of sand

Subphylum Urochordata

Tunicates or sea squirtsShort larval stage is a motile bilateraterian with all chordate

characteristicsLasts until suitable substrate found when metamorphosis occurs

Adult is sessile with degenerated NS, resorbed notocord and tail

Suspension feeders

Craniates

Chordates with a head containing a brain at anterior end of nerve cord, eyes and sensory organs

Neural crest distinguishes craniates from other chordatesCollection of cells near closing neural tube in developing

embryosCells give rise to teeth, bones of skull, facial dermis, and

neuronsPharyngeal slits into gill slits which allow sucking food and

gas exchangeHigher metabolism, extensive muscles, 2+ chamber heart,

RBC’s with hemoglobin, and kidneys

MyxiniCartilaginous skull

without jaws or vertebrae

Muscles against notocord for movement

Small brain, eyes, ears, nasal opening, and tooth-like formations of keratin

Bottom dwelling scavengers

Slime glands

VertebratesMore extensive skull Backbone of vertebrae

Encloses spinal cord and replaces notocord function

Skeletons evolved initially as unmineralized cartilageFirst structures were dental elements

Allowed animals to become scavengers and predators

Aquatic species developed dorsal, ventral, and anal fins to provide steering control

More efficient means of gas exchange

Lampreys

Parasites clamp on with jawless mouth and bore into fish to suck blood

Larvae is freshwater filter feederSome feed as larvae only before reproducing and dying

Cartilaginous skeleton with no collagen in its matrixNotocord is main axial structure surrounded by cartilage

Dorsal projections partially enclosing nerve cord

Gnathostomes

Jawed animals that are aided by teeth to grip and slice foodEvolved from skeletal rods that supported anterior gill slits

Forebrain enlargement associated with enhanced vision and smell

Lateral line systemOrgans form rows on either side of body and sense vibrations in

waterPaired fins and tail enhance swimming after prey

Class ChondrichthyansEndokeleton composed of

cartilage and Ca+

Bone traces in scales, teeth, and vertebrae surfaces

SharksSwift, but unagile awimmersBouyancy from oil stored in liver,

but must stay swimmingContinually replace teeth as lostSpiral valve increases SA of

digestive tractEnhanced sensesInternal fertilization of eggs

Oviparous: lay eggs in protective cases that hatch outside mother

Ovoviviparous: retain fertilized eggs in oviducts, nourished by yolk

Viviparous: develop in uterus provide nutrients through a placenta

Rays

Class OsteichthyansOssified endoskeleton with matrix of calcium

phosphateGills for gas exchange, protected by an

operculumBuoyancy from a swim bladder, or air sac,

with gas exchange to control rise and fallSkin covered by bony scalesSkin glands secrete mucus to skin to reduce

dragMost species are oviparous

Reproduce by external fertilization after female sheds eggs

ActinopterygiiRay-finned fishesModified for

maneuvering and defense

Originated in fresh water and spread to seasSalmon and trout

between salt and fresh water

Human source of protein

SarcopterygiiLobe-fin fishesMuscle surrounds rod-

shaped bonesFor swimming and

‘walking’ across underwater substrate

Coelacanths still survivePreviously thought

extinctLungfishes

Surface to breathe, but gills for gas exchange

Tetrapods

TetrapodsLimbs that support weight

on landDigits on feet to create

forces with groundHead separated from neck

1 vertebrae allowed up and down, 2 allowed side to side

Pelvic girdle fused to backbone to transfer leg forces to body

Pharyngeal slits become ears and glands

Class AmphibiaSalamanders and newts

Some entirely aquatic, others on land or throughout life

On land use side-to-side motionFrogs and toads

Hind legs to jumpInsects and prey caught with tongueSkin glands secrete mucous for

protectionColor variations as warnings or

camouflageCaecilian

Legless and nearly blindAbsence of legs are secondary

adaptations

‘Amphibians’Life on land and waterHerbivorous tadpole is the larval stage of frogs

Has gills, lateral line system, and long finned tail; no legsMetamorphosis into a carnivorous adult

Develops legs, lungs, external ear drums, and a digestive system; lost gills and lateral line system

Salamander and caecilian larvae resemble adult and both stages carnivorous

Necessary for skin to stay moist for gas exchangeExternal fertilization in frogs

Eggs laid in moist environments to prevent desiccationOviparous and viviparous species

Complex social behavior, ectothermic, cloaca, and 3-chambered heart

AmniotesAmniotic egg with 4

membranesDevelop from tissue layers

growing from embryoAllows embryonic

development on landEggs with shells

Differs in birds and reptilesMammals develop embryo

without egg inside femaleRib cage helps ventilate

lungsAbandon skin breathing and

conserve water

Class ReptiliaScales of keratin to protect from desiccation and

abrasionEggs on land after internal fertilization

ViviparousEctotherms use heat absorbing behavior instead

of metabolism to regulate body temperature Turtles

Box-like shields fused to vertebrae, clavicles, and ribsNeck retraction is horizontal or vertical Incubation temperature can determine sex

Crocodilians4 chambered hearts and developed kidneys for

excretionLizards

Often carnivorous

SnakesForce for movement from bending against

objects to move forwardLack ears, but sensitive to ground

vibrationsInfrared detectionAll carnivorous with teeth for griping and/or

injecting venomJacobs organFlexible airway, loosely articulated jaw, and

elastic skin to swallow prey

Class AvesFeatures adapted for flightLack urinary bladders, females with 1 ovary, reduced gonads in

both sexes except in breeding season, lightened bones, and toothless

Feathers are β-keratin (modified scales) arranged into airfoilsSome adapted for soaring others require constant flappingFlightless birds are missing sternal keel and developed muscles

Enhanced hunting and scavenging, protection, and food resource attainment

Energetically expensiveEndothermic animals with layers of fat to provide insulation

Efficient respiratory and circulatory system with 4-chambered heart

Acute vision and muscle control with larger brainComplex behavioral displays, often related to breeding Internal fertilization via ‘cloacal kiss’

Brooding keeps eggs warm

Class MammaliaMammary glands and hairEndothermic with high metabolic ratesEfficient respiratory and circulatory system

with 4-chambered heartDiaphragm to help ventilate lungsLarger brains and differentiated teeth3 lineages

Monotremes are egg-layingMarsupials have a pouchEutherians are placental mammals

MonotremesOnly in Australia and

New Guinea1 species of platypus4 species of echidnas

(spiny anteaters)Lay eggs, but

produce milk and have hairNo nipples, milk from

glands at belly that young suck

MarsupialsHigher metabolic rates

and nipplesGive birth to live young

Born early and complete development while nursing in pouch

Most live in AustraliaOpossums only ones in

North America

EutheriansLonger pregnancy

Embryonic development completed in uterusNurtured by placenta

Order PrimatesOpposable thumb and big toe

Aids grasping and manipulation behaviorsAdapted for arboreal (tree-dwelling) life

Flat nails and not clawsReduced olfaction, but increased reliance on

visionSmaller noses, but larger eyes in front close together

Smaller litter size, longer gestation, increased maternal care

Fewer teeth, but specialized2 incisors, 1 canine, 3 premolars, and 3 molars in

each quadrant2 taxonomic arrangements (generally)

ProsimiansLemurs

Only in MadagascarEvolved in isolationPrimarily nocturnal

LorisesAfrica and southern AsiaAll nocturnal

TarsiersSpecialized for vertical climbing and leapingSoutheast Asia and IndonesiaDiet is almost completely animal matter

Tarsier

Loris

Ring-tailed lemur

AnthropoidsMonkeys (not monphyletic)

Active during the day and live in socialbands

Forelimbs about equal length ashindlimbs

New world All arboreal Central and South America Nostrils wide open and far apart Long prehensile tail-specialized for grasping

tree limbsOld world

Ground dwelling and arboreal Africa and Asia Lack prehensile tail Nostrils open downward

Hominoids (Apes)

Hominoids (Apes)Lack tailsLong arms and short legsMainly vegetarians

Humans are omnivorous, eating plants and animals

More flexibleLarger brain relative to body sizeHigh degree of social organization5 divisions

Hominoid DivisionsGibbons

9 species all in Southeast AsiaOnly entirely arboreal apesSmallest, lightest and most acrobaticMonogamous for life

OrangutanSolitary species in rain forests of Sumatra and BorneoLargest arboreal mammal, occasionally move on ground

GorillasLargest ape found only in African rainforestsLive in groups of up to 20Stand upright, walk on 4 legs with knuckles on the

ground

Hominoid Divisions (cont.)

Chimpanzees (and bonoboos)Knuckle walkersTropical AfricaBehavior closely mirrors humans

Make simple toolsRespond to mirrors

Can learn human sign languageHumans

Bipedal, larger brain, capable of language, thought, and complex tools

Humans didn’t evolve in a direct path. Dead end groups broke off and ended in extinction; except for us.