Chapter 19

Chordate Characteristics

Dorsal, hollow nerve cordsNotocord between GI tract and nerve

cordPharyngeal slits Post-anal tail

Phylum ChordataSubphylum Urochordata

Sea squirtsAdult has pharyngeal slits only, larva has all fourNo brain

Subphylum CephalochordataLancelets Suspension feedersMucus net to trap foodSimplistic brain, swollen tip of

nerve cordSubphylum Craniata

Species with a head containing a brain, sensory organs, and a skull

Development of Vertebrates

Class Agnatha (Jawless fish)Chordates with heads, no jaws, and a notocord for

supportHagfishes

Nearly blind, but excellent sense of smell and touchEnter holes in prey or create holes with tooth structuresTies tail in knots or secretes slime for feeding and

protectionLampreys

Larvae are suspension feeders that live in sedimentMost are parasitic to fishes

Attach to sides of fish and feeds on tissue and bloodFrom ocean to Great Lakes by St. Lawrence Seaway

Class Chondricthyes (Cartilaginous fishes)Flexible skeletons of cartilageLateral line system to detect changes in water

pressure and vibrationsSharks

Detect prey through electrosensor s on their headSharp vision and keen smell

RaysSuspension feedersDorsoventrally flattened with eyes on top of headTails have spines that have venom glands

Class Osteichthyes (Bony fishes)Ray-finned fishes

Skeleton made of bone including the ray finsOperculum , protective flap covering the gills

Can breathe without swimming, contrast shark Swim bladder, lung-derived organ to keep them afloat Adaptaions based on environment

Female seahorses deposit eggs in male’s pouch to develop

Lobe-finned fishesRod shaped bones in pectoral and pelvic finsCoelocanth, lungfishes, and tetrapods

Class AmphibiaDamp habitats so water can supplement for lungsSkin has poison glands and coloration for defenseDistribution limited by vulnerability to

dehydrationCaecilians

Nearly blind and leglessLive in moist tropical areas

FrogsMost adult life on land

Lay eggs in water and juveniles (tadpoles) live in water until metamorphosis

Toads have rough skin and entirely terrestrialMating calls during breeding season

Class ReptiliaAmniotes, eggs develop in protective sacsInclude lizards, snakes, turtles, crocodilians, and

dinosaursSkin with scales and waterproofed by keratin‘Cold-blooded’ so metabolism doesn’t make heat

Ectothermic absorbs heatDinosaurs may have been endothermic, using

metabolismSnakes lost legs due to burrowing natureCrocodilians most time in water with nostrils out

Class AvesEvolved from small, 2-legged dinosaurs (therapods)Body adapted for flight, strong but light

No teeth, tail has few vertebrae, feather shafts hollow, and honeycombed bones

Feathers provide lift and maneuverabilityHigh metabolism for energy demands of flightEndothermic so feathers act as insulationHighly efficient circulatory system, lungs, and visionComplex behavior, both sexes incubate eggs and

feed

Class MammaliaHair and mammary glands that produce milk

Endothermic so hair acts to insulateEfficient respiratory and circulatory systems

for high metabolismLarge brain and long parental careDifferentiation of teeth for variety of foodsOffspring are hatched or birthed

Order Monotremata (Monotremes)Egg-laying mammalsDuck-billed platypus

and spiny anteaters are only existing members

Subclass TheriaEmbryo is nurtured in the mother by a placenta

Allows nutrients to diffuse between mother’s and embryo’s blood

Infraclass Metatheria (Marsupials)Brief gestationTiny offspring that develop in an external pouch

Infraclass Eutheria (Eutherians)Bear fully developed live youngPlacental animals because more complex then

marsupials

Order Primates (Human order)Opposable thumb and big toe

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

Flat nails and not clawsReduced olfaction, but increased reliance on vision

Smaller noses, but larger eyes in front close togetherSmaller litter size, longer gestation, increased

maternal careFewer teeth, but specialized

2 incisors, 1 canine, 3 premolars, and 3 molars in each quadrant

2 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 monophyletic)

Active during the day and live in social bandsForelimbs about equal length as hindlimbsNew world

Central and South America Nostrils wide open and far apart Long prehensile tail-specialized for grasping tree

limbsOld world

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

groundGorillas

Largest 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 baboon)

Knuckle walkersTropical AfricaBehavior closely mirrors humans

Make simple tools Respond to mirrors

Can learn human sign languageHumans

Hominid fossils found that are closer to humans than chimpanzees Human evolutionary branch, but don’t confuse with hominoid

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

From Hominoid to HominidInitial theory

Increased brain size credited with divergence Led to changes in food-gathering skills, parental care, and

social interactionsBipedalism, upright walking , afterwards

Hypothesis untested till female skeleton, ‘Lucy’, foundBipedilism conclusively shown to emerge first

Opening at base of skull supports upright evolution Quaprepeds have openings that angle back

Stephen Gould, “mankind stood up first, and got smart later.”

From Hominid to HomoEvidence from fossils and comparing to earlier speciesIncreased skull size relative to brain can estimate

brain size which can indicate intelligenceComplexity of tools foundChanges in teeth and jaws

Smaller to adapt to meat eating and allow brain growth in skull

Long, slender legs with hip joints for distance walkingNarrow pelvis constrained fetal head size so parental

care needed for longer

Homo sapien SpreadAll living humans suggested to originate from

ancestors in AfricaMitochondrial DNA, inherited maternally

All trace to one common womanY chromosomes, passed from father to son

Mutations can serve as markers for ancestry

Believed to spread because of increased cognitionCapacity to speak strong factor

Emergence of SpeechHuman language is unique

Other animals vocalize sounds to communicateHuman communication is more complex which

creates societies with shared languageUsed in concrete and abstract ways

FOXP2 gene linked to a family with impaired speech and brain developmentFound in other species

Humans and song-birds are most similar Both learn vocalization from others of the species

Linked to brain development of speech areaOther genes contribute, but connected to

passing on

Skin ColorSkin color varies geographically

One of the most striking differencesNot genetically distinct

Results from melanin, a pigment of specialized skin cellsActivity levels effect degree of pigmentationAbsorbs visible and UV light

Synthesizes vitamin D, necessary for bone development Less pigment adapted to maximize vitamin D as moved north

Protects folate degradation Necessary for fetal development Damaged by UV light

Pigmentation Trade OffHypothesized as an

adaptation trade offBalanced folate

protection with vitamin D production

Similar environments have similar pigmentationsNot a useful

phylogenetic character