Evolution of Vertebrates
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Transcript of Evolution of Vertebrates
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
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