Download Evolution of Vertebrates

Chapter 19
Chordate Characteristics
 Dorsal, hollow nerve cords
 Notocord between GI tract and nerve cord
 Pharyngeal slits
 Post-anal tail
Phylum Chordata
 Subphylum Urochordata
 Sea squirts
 Adult has pharyngeal slits only, larva has all four
 No brain
 Subphylum Cephalochordata
 Lancelets
 Suspension feeders
 Mucus net to trap food
 Simplistic brain, swollen tip of
nerve cord
 Subphylum 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 support
 Hagfishes
 Nearly blind, but excellent sense of smell and touch
 Enter holes in prey or create holes with tooth structures
 Ties tail in knots or secretes slime for feeding and protection
 Lampreys
 Larvae are suspension feeders that live in sediment
 Most are parasitic to fishes

Attach to sides of fish and feeds on tissue and blood
 From ocean to Great Lakes by St. Lawrence Seaway
Class Chondricthyes (Cartilaginous fishes)
 Flexible skeletons of cartilage
 Lateral line system to detect changes in water
pressure and vibrations
 Sharks
 Detect prey through electrosensor s on their head
 Sharp vision and keen smell
 Rays
 Suspension feeders
 Dorsoventrally flattened with eyes on top of head
 Tails have spines that have venom glands
Class Osteichthyes (Bony fishes)
 Ray-finned fishes
 Skeleton made of bone including the ray fins
 Operculum , protective flap covering the gills
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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 fishes
 Rod shaped bones in pectoral and pelvic fins
 Coelocanth, lungfishes, and tetrapods
Class Amphibia
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Damp habitats so water can supplement for lungs
Skin has poison glands and coloration for defense
Distribution limited by vulnerability to dehydration
Caecilians
 Nearly blind and legless
 Live in moist tropical areas
 Frogs
 Most adult life on land

Lay eggs in water and juveniles (tadpoles) live in water until
metamorphosis
 Toads have rough skin and entirely terrestrial
 Mating calls during breeding season
Class Reptilia
 Amniotes, eggs develop in protective sacs
 Include lizards, snakes, turtles, crocodilians, and
dinosaurs
 Skin with scales and waterproofed by keratin
 ‘Cold-blooded’ so metabolism doesn’t make heat
 Ectothermic absorbs heat
 Dinosaurs may have been endothermic, using metabolism
 Snakes lost legs due to burrowing nature
 Crocodilians most time in water with nostrils out
Class Aves
 Evolved 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 maneuverability
 High metabolism for energy demands of flight
 Endothermic so feathers act as insulation
 Highly efficient circulatory system, lungs, and vision
 Complex behavior, both sexes incubate eggs and feed
Class Mammalia
 Hair and mammary glands that produce milk
 Endothermic so hair acts to insulate
 Efficient respiratory and circulatory systems for high
metabolism
 Large brain and long parental care
 Differentiation of teeth for variety of foods
 Offspring are hatched or birthed
Order Monotremata (Monotremes)
 Egg-laying mammals
 Duck-billed platypus
and spiny anteaters are
only existing members
Subclass Theria
 Embryo is nurtured in the mother by a placenta
 Allows nutrients to diffuse between mother’s and
embryo’s blood
 Infraclass Metatheria (Marsupials)
 Brief gestation
 Tiny offspring that develop in an external pouch
 Infraclass Eutheria (Eutherians)
 Bear fully developed live young
 Placental animals because more complex then marsupials
Order Primates (Human order)
 Opposable thumb and big toe
 Aids grasping and manipulation behaviors
 Adapted for arboreal (tree-dwelling) life
 Flat nails and not claws
 Reduced olfaction, but increased reliance on vision
 Smaller noses, but larger eyes in front close together
 Smaller litter size, longer gestation, increased maternal care
 Fewer teeth, but specialized
 2 incisors, 1 canine, 3 premolars, and 3 molars in each quadrant
 2 taxonomic arrangements (generally)
Prosimians
 Lemurs
 Only in Madagascar
 Evolved in isolation
 Primarily nocturnal
 Lorises
 Africa and southern Asia
Loris
 All nocturnal
 Tarsiers
 Specialized for vertical climbing and leaping
 Southeast Asia and Indonesia
 Diet is almost completely animal matter
Ring-tailed lemur
Tarsier
Anthropoids
 Monkeys (not monophyletic)
 Active during the day and live in social bands
 Forelimbs about equal length as hindlimbs
 New world
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Central and South America
Nostrils wide open and far apart
Long prehensile tail-specialized for grasping tree limbs
 Old world
 Africa and Asia
 Lack prehensile tail
 Nostrils open downward
 Hominoids (Apes)
Hominoids (Apes)
 Lack tails
 Long arms and short legs
 Mainly vegetarians
 Humans are omnivorous, eating plants and animals
 More flexible
 Larger brain relative to body size
 High degree of social organization
 5 divisions
Hominoid Divisions
 Gibbons
 9 species all in Southeast Asia
 Only entirely arboreal apes
 Smallest, lightest and most acrobatic
 Monogamous for life
 Orangutan
 Solitary species in rain forests of Sumatra and Borneo
 Largest arboreal mammal, occasionally move on ground
 Gorillas
 Largest ape found only in African rainforests
 Live in groups of up to 20
 Stand upright, walk on 4 legs with knuckles on the ground
Hominoid Divisions (cont.)
 Chimpanzees (and baboon)
 Knuckle walkers
 Tropical Africa
 Behavior closely mirrors humans
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Make simple tools
Respond to mirrors
 Can learn human sign language
 Humans
 Hominid fossils found that are closer to humans than
chimpanzees
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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 Hominid
 Initial theory
 Increased brain size credited with divergence

Led to changes in food-gathering skills, parental care, and
social interactions
 Bipedalism, upright walking , afterwards
 Hypothesis untested till female skeleton, ‘Lucy’, found
 Bipedilism conclusively shown to emerge first
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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 Homo
 Evidence from fossils and comparing to earlier species
 Increased skull size relative to brain can estimate brain
size which can indicate intelligence
 Complexity of tools found
 Changes in teeth and jaws
 Smaller to adapt to meat eating and allow brain growth in
skull
 Long, slender legs with hip joints for distance walking
 Narrow pelvis constrained fetal head size so parental care
needed for longer
Homo sapien Spread
 All living humans suggested to originate from
ancestors in Africa
 Mitochondrial DNA, inherited maternally
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All trace to one common woman
 Y chromosomes, passed from father to son
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Mutations can serve as markers for ancestry
 Believed to spread because of increased cognition
 Capacity to speak strong factor
Emergence of Speech
 Human language is unique
 Other animals vocalize sounds to communicate
 Human communication is more complex which creates
societies with shared language
 Used in concrete and abstract ways
 FOXP2 gene linked to a family with impaired speech
and brain development
 Found in other species
 Humans and song-birds are most similar
 Both learn vocalization from others of the species
 Linked to brain development of speech area
 Other genes contribute, but connected to passing on
Skin Color
 Skin color varies geographically
 One of the most striking differences
 Not genetically distinct
 Results from melanin, a pigment of specialized skin cells
 Activity levels effect degree of pigmentation
 Absorbs visible and UV light
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Synthesizes vitamin D, necessary for bone development
Less pigment adapted to maximize vitamin D as moved north
 Protects folate degradation
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Necessary for fetal development
Damaged by UV light
Pigmentation Trade Off
 Hypothesized as an
adaptation trade off
 Balanced folate
protection with
vitamin D production
 Similar environments
have similar
pigmentations
 Not a useful
phylogenetic
character