Vertebrate Evolutionary Morphology

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Homology

Back 1

Homologous structures in related organisms derived from common ancestry.

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Serial Homology

Back 2

Repeated similar structures within an organism derived from primary body segments (vertebrae, etc)

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Analogy

Back 3

Structures with similar function and appearance, but without common genetic basis

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Homoplasy

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Similarity that isn't homologous or analogous.

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Convergence of traits happens when...

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When there are limited morphological solutions to an environment. (fish form)

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Vertebrate

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Bilateral symmetry
Primary body segmentation
Dorsal hollow nerve cord
Post-anal tail
Pharyngeal gill slits
V shaped myomeres
Well developed head
Appeared in middle-early cambrian (500MYA)

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Cladogram

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Branch Diagram
Used for showing common ancestors
Strong with existing groups
Weaker with extinct because less data, difficulty recognizing convergent evolution

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Parsimony

Back 8

Evolution always takes the minimum number of steps

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Palezoic Era

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544MYA-254MYA

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Cambell's
Onion
Soup
Did
Made
Peter
Puke

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Cambrian 544-505
Ordovician 505-440
Sularian 440-410
Devonian 410-360
Mississippian 360-325
Pennsylvanian 325-286
Permian 286-245

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Appearance of major chordate groups in fossil record
Cambrian
Ordovician
Silurian

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Cambrian = First chordates / vertebrates 520-530MYA
Ordovician = first bone, agnathans (jawless fish with bony exoskeletons) 470MYA
Silurian = First gnathostomes (jawed vertebrates), sharks, rays, holocephalans

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Appearance of Taxa
Late Devonian
Carboniferous
Late Triassic
Jurassic
Cretaceous

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D = Tetrapods (amphibians)
C = Amniotes (reptiles), which split into synapsids & sauropsids)
T = First mammals, dinosaurs, frogs, turtles, crocodilians
J = Birds, lizards
Cret = Snakes

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Endoderm

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Forms lining of gut

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Mesoderm

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Forms connective tissues and muscle

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Ectoderm

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Forms neural tisue, epidermis and sense organs

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Protostome

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Mouth First. Mostly spiral cleavage

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Deuterostome

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Mouth Forms Second. Embryonic opening of gastrula (blastopore) forms anus. Radial Cleavage

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Coelomates

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Have fluid-filled body cavity lined by mesoderm

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Chordate

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Notochord: elastic rod, allows side-to-side flexing
2) pharyngeal slits: feeding/respiratory
3) dorsall-positioned tubular nerve cord
4) post-anal tail
5) segmented myomeres(blocks of skeletal muscle)

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Urochordata

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1 of 3 subphyla of chordata
Tunicates, Sea Squirts
Adults sessile filter feeders
pharyngeal basket for filtering food
larvae are free-living motile with chorate characters (sense, locomotion)

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Lancelet

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Subphylum chordata
Cosmopolitan distribution in warm & tropics
small sessile marine filter feeders
cilia move water across pharyngeal apparatus, functions primarily in feeding

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Craniata

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Evolutionary pressures result in increased size, activity, and integration of sense and locomotion abilities. Vertebrates begin to enter water column and become dominate marine predators.
Major adaptive radiation of jawless vertebrates in late Ordovician

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Centrum

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Cylindrical body of the vertebra

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Craniate innovations

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Brain from elaboration of anterior end of nerve tube
Bone/cartilage that protects brain
paired sense organs (eyes, nose)
Neural Crest Cells

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Neural Crest Tissue

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specialized embryonic tissue. Forms in the embryonic neural tube, then migrates and contributes to the formation of sense organs, peripheral nervous system, pigment

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Cephalization brought about a 3 part brain

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fore = nose
mid = eyes
hindbrain = ears

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For Vertebrate classification:
Kingdom
Phylum
Subphylum

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Animalia
Chordata
Vertebrata(craniata)

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For Vertebrate classification:
Class

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Agnatha
Placodermi
Chondrichthyes
Acanthodii
Osteichthyes
Amphibia
Reptilla
Aves
Mammalia

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Class Agnatha

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Lampreys and hagfish
Myxini = hagfish
Highly specialized scavengers that lack bone. Body is iso-osmotic to seawater, use thick slime as defense. Craniates (but not vertebrates) Have cartilaginous braincase, but no notochord support.

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Petromyzontiformes

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Lampreys, specialized predators of bony fish. round, sucking mouth with tongue, keratinous teeth, muscular pharynx to suck blood. No bone in living agnathans, but many extinct ones with bony exoskeleton.

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Conodonts

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First bone. Found many tiny bony tooth-like structures. Soft-bodied vertebrates.

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Primitive dermal bone

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Enamel covering dentine on outer layer
Middle layer is spongy bone
Basal layer is laminated acellular bone

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Gnathostomes

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Origin of jaws, likely evolved from supporting bones or cartilages of anterior gill arches.
Paired fins, anterior pectoral and posterior pelvic fins. Associated with pectoral and pelvic girdles in body wall. Selection for increased stability & maneuverability.

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Placoderms

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First gnathostome found in 430MYA. Extensive fused plates of dermal bone on head and trunk. Notochord with ossified neural and hemal arches and lacking bony centrum. Evidence of internal fertilization & live birth. Similar to sharks. Disappeared by mid Carboniferous.

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Ossification

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Laying down new bone

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Chondrichthyes

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Sharks, Rays, chimeras. Cartilaginous endoskeleton (calcified) Lacks bone, has placoid scales. Large liver for buoyancy, large pectoral fins for lift, conveyor belt tooth replacement. Internal fertilization

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Placoid Scale

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"small tooth" Bony base, cone-shaped dentine crown over enamel over inner pulp cavity.
Develops in dermis, erupts through skin.

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Lamprey & Hagfish additional info

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PRIMITIVE: Lack bone, retain notochord, lack jaws, paired median fins, less than 7 pharyngeal slits, 1-2 semicircular canals in inner ear, monomeric hemoglobin, hagfish are osmo-conformers.
DERIVED: specialized life history (anadromy, ectoparasitic, complex metamorphosis. Modified feeders & respiratory, hagfish slime and knotting strategies.

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Osteichthyans

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Bony fish, most have highly ossified endoskeletons, early forms has simple lungs, fossil traces from early Silurian deposits, advanced modern species with gas filled swim bladders

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Osteichthyes break down into Actinopterygians

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Actinopterygians (ray finned) fish
most species of existing vertebrate group. fins supported by bony rays, movement controlled by muscle in body wall

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And Sarcopterygians

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Lobe-finned fish, 3 extant species of lungfish (dipnoi) Late Palezoic-Mesozoic diversity. Skull specialized for powerful bite. Can aestivate. Peak diversity in Devonian. Most gone 65MYA

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Lobe finned fish into 2 groups
Crossopterygians and Dipnoans

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Single living species, coelacanths only group to survive Paleozoic. Advanced crossopterygians approach tetrapod condition.

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Acanthostega

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360 MYA, Earliest forms highly aquatic. Generally poorly adapted to come onto land, anatomically intermediate between lobe-finned fish and full tetrapods. Pelvic region was fused and gave it more power.

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Osteichthyans

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Bony fish, most have highly ossified endoskeletons, early forms has simple lungs, fossil traces from early Silurian deposits, advanced modern species with gas filled swim bladders

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Osteichthyes break down into Actinopterygians

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Actinopterygians (ray finned) fish
most species of existing vertebrate group. fins supported by bony rays, movement controlled by muscle in body wall

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And Sarcopterygians

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Lobe-finned fish, 3 extant species of lungfish (dipnoi) Late Palezoic-Mesozoic diversity. Skull specialized for powerful bite. Can aestivate. Peak diversity in Devonian. Most gone 65MYA

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Lobe finned fish into 2 groups
Crossopterygians and Dipnoans

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Single living species, coelacanths only group to survive Paleozoic. Advanced crossopterygians approach tetrapod condition.

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Acanthostega

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360 MYA, Earliest forms highly aquatic. Still had aquatic tail, low to ground.

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Origin of amniotes

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amphibian reproduction: external fertilization, fish-like eggs, aquatic larvae

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Carboniferous tetrapods(cotylosaurs)

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evolved extra embryonic membranes (egg shells).
Amnion: surrounds, bathes embryo in fluid
Yolk sac: provides nutrients for development
allantois: metabolic wastes, gas exchange
Chorion: peripheral membrane

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Synapsids

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Amniote with single temporal fenestra
Large left aortic arch
bronchoalveolar lungs
specialized teeth

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Sauropsids (all other amniotes

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Right aortic arch emphasized, septate lungs, posess anapsid or diapsid skulls.
Anapsid (basal reptiles and turtles)
lepidosaurs: lizards, snakes
archosaurs: crocodilians, dinosaurs, birds

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Anapsid
Synapsid
Diapsid
Euryapsid

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No temporal fenestra
One
Two (stacked)
One (at the top)

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Allometry

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Proportional and predictable change in dependent variable (shape, metabolic rate) with change in independent variable (usually size/mass)

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Isometric scaling

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Pattern in growth where shape does not change with increase in size (rare)
desmognathine salamanders, some pterosaurs.

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Integument
Epidermis

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Skin, largest organ, poorly vascularized, limited innervation, regenerates, (ectodermal origin)
Dermis (derived from mesoderm/dermatome) dense fibrous connective tissue, highly vascularized, well innervated, bone, dentine (25% organic) forms in dermis.

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Integument

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Barrier to pathogens
Mechanical protection
Reduction of water loss
Thermoregulation
Respiration
Muscle attachment
Sensory
Sexual Signaling

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Bony fish had integument with 4 layers

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superficial enameloid
dentine
vascular spongy bone
lamellar bone

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Placoid Scale

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Ganoid Scale

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Cosmoid Scale

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Similar to bony armor of ostracoderms
Overlapping scales with light enamel coat overlaying dentine.

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Teleost fish scale types
Cycloid
Ctenoid

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Concentric rings of lamellar bone
comb-like fringe on posterior surface

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Reptile Skin

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Cornified epidermis.
Stratum germinativum=freshest layer
s. granulosem=keratin infused mid
s. corneum=dead section, highly keratinized.
old skin shed as sheets in lizards while new epidermis develops beneath.

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Birds

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Thin, glandular skin with feathers
uropygial gland at base of tail (lipoprotein for preening & feather care)
Feathers for flight, insulation, sexual display, evolutionary derivation from reptillian scales. Develops in follicles from invaginations of epidermis. Root nourished by dermal papillae, beta keratin highly durable protein.

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Feather

Back 65

Calamus (quill)
rachis (shaft)
barbs, barbules, hooklets