Download Chordata -Pharyngeal slits -Notochord

Chordata
-Pharyngeal slits
-Notochord
-Dorsal hollow nerve chord
-post anal tail
Vertebrata
-Pharyngeal slits
-notochord
-Single dorsal hollow nerve cord
-post anal tail
-bilaterally symmetrical
-cephalization
-coelom
-closed circulatory system
-most have endoskeleton
-appendages
-genital and excretory system
Cephalochordata
-Amphioxus
-no paired fins
-notochord – no cranium
-major blood vessels
-digestive tract
-pharyngeal slits
Urochordata
-a large pharynx
-inhalent, exhalent siphons
-most sessile
Larvae form urochordata
-larval form tadpole like
-pharyngeal slits
-muscular post anal tail
-dorsal hollow nerve cord
-notochord
-free swimming
Paedomorphosis
-sexually mature with larval characteristics
-larval form acquired number of changes
-elongation
-slits in pharynx
-segmented muscles
-bone
Evidence
-pelagic larvae
-one way gut
-bilaterally symmetrical
EXAMPLE mount seymore brown salamander
-spends a year in water in larval stage
-higher elevation, never becomes terrestrial
Classification
KPCOFGS
Kids play catch on farmer greens shed
Kingdom,Phylum,Class,Order,Family,Genus,Spe
cies
Overview of 9 classes of vertebrates
Agnatha – jawless fish
-Head with cranium, brain, paired eyes
-Vertebrate – cartilaginous elements on dorsal
surface of notochord
-bones present as scales, armor in some
-mouth, but no jaws, no true teeth
-no pectoral or pelvic girdle
-have pectoral spikes or folds
-no appendages
-gills in pouches
-Living agnathans (lamprey, hagfish)
-Larval form of lamprey very similar to ancestral
body plan of vertebrates
Placodermii (=plate skin)
-Extinct group of fishes
-covered with bony armor
-anterior of body(head)
-head joint to body by hinge in armor (can tilt
head up)
-persistant notochord
Novel features
-Jaws enlargement and adaptation of a visceral
arch larger, harder food
-paired appendages
-gas bladder
Chondrichthyes
-skates, rays, sharks, chimaera (ratfish)
-very little or no bone
-modern species cartilaginous
-small toothlike scales called denticles
Made of dentine and enalmel
-multiple external gill slit openings
-no gas bladder, use liver for bouncy
-paired nostrils blind olfactory sacs
-teeth anchored to skin at margin of jaws
Acanthodii “stout” spines
-numerous paired fins
Thin membrane supported stout spines
-all extinct
-streamlined bodys, large eyes, wide mouth
with many teeth, bony head, small hard scales
 active swimmers and predators
Osteichthyes
-evolved from an ancestor common with
acanthodian 400 mya
-last 250 mya dominant fish
most abundant vertebrates on earth
-bone – skull, vertebrae, girdle, fin, scales
-have some cartiledge
-gills in bony operculum
-either have a lung or gas bladder for bouncy
Paleoclimates
-major influence on evolutionary success of an
organism
-well adapted will survive
-late Cambrian, major extinction of marine
inverts
-carboniferous first “amphibian” non amniotic
tetrapods
-Mid carboniferious – first amniote, first no
amniotic egg sac reptile to have amniotic eggs
-Late carboniferous – amniotes splits into
ancestors of mammals and birds/reptiles
-Late Permian mass extinctions 95% of all
marine species
CLASS AGNATHA
-earliest vertebrates
-paraphyletic assemblages of jawless fish
“ostracoderms”
Three major groups
-cambrian agnatha
-ostracoderms
-cyclostomata
Cambrian agnathans
Vertebrate characteristics
-cranium
-w shaped myomeres
-notochord with vertebral element “cartiledge”
-sense organs clustered in head region
-branchial arcdhes
appear more derived than hagfish
-no bone or mineralized scales
Ostracodermata
-pharaphyletic assembelage
-all had coverings of dermal bone
-cerebellum present (not present in
hagfish/lamprey)
-no jaw (some had moveable mouth plate)
-midlien dorsal fin
-msucle pharyngeal pump
-gillls
-2 semicircular canals
Divide into 2 groups
A. pteraspida
-headshield of fused body plates
-lateral and dorsal spines on shield
-not fins but part of the armor
-spines stopped “rolling”
-post cranial exoskeleton
-no paired appendages/dorsal/anal fins
-hypocercal tail
Evolutionary trends
increased efficiency in locomotion
increased feeding efficiency
Cephalaspida
-body shapes a lot diff body shape means basic
biology is different
-heavily armored headshield and smaller plates
on body
-headshield all same size, speculate shield
develops when fully grown
-fusiform or flattened body
-most have hypocercal tail
-live on bottom of ocean
-stabilizing projections or folds
Xinoidea (hagfish)
-lack vertebrae
-scaleless
-2 horny plates border sides on tongue like
structure
pincer like action
-1-15 gill opening – no relationship with gills
and gill openings
-kidney – primitive vertebrae system
-accessory hearts, blood sinuses, low blood
pressure
-very few immune reactions
Lamprey
-andromous, lay eggs upstream live in large
body of water
-parasitic
-larvae filter feeders
Characteristics
-small vertebral elements
-7 gill pouches, tidal respiration
-primitive vertebrate nervous system
-Chloride cell in gill and kidney for regulation
and nnitrogenous waste
Lamprey larvae (ammocoetes) and amphioxus
-larval form
Similarities
-notochord
-dorsal hollow nerve chord
-segmented muscles
-straight instetines
-pharyngeal gill slits
-postanal tail
Differences
-eyespot present in amphioxus
-brain more complex in ammocoetes
-7 vs 50 gillslits
-pharynx has muscles and cartilaginous skeleton
Hard mineralized tissue are ancestral vertebrate
structures
Advantages
-calcium and phosphorous reserves
-efficient movement
-protection
-buffers for blood
-increase body weight, keep you where food is
Skeletal support elements
-notochord
-cartiledge
-bone
Notochord
-sheet of fluid filled cells
-first structural support tissue
-present in all vertebrae
Cartiledge
-less salt than bone
-cells lack connection between cells
-deep lying tissue, below skin
-embryos and young vertebrates
-cyclostomata, chondritcheyes, few
osteichthyes
Bone
Types of bone
Dermal Bone
-forms directly over mesenchyme, no
cartilaginous precursors
-thin plates of collagen matrix, salts deposited
-plates expand outer margin and thicken by
adding new layers on inner and outer surface
-bones of the skull, pectoral girdle
Replacement bone
-Bones can replace cartildge = replacement or
endochondral bone
-osteoblast enters along the blood vessel
-typical of vertebrate long bones
-bone can also be added to the margins and
other surfaces
Mineralized tissue
-Three types
-bone
-dentine
-enamel
Bone
- always found deep in dermis
-25-30% organic matter
-cells alive in matrix
Dentine
-mesoderm-ectoderm boundary by mesodermal
cells
-internal to enamel and external to bone
-teeth, denticles, scales, external armor
-inorganic salts of hydroxypatite
-25% organic matter
-harder than bone
-cells do not stay in matrix
Enamel
-hardest tissue in vertebrate body
-produced by ectoderm on top of dentine
-teeth, superficial denticles, scales, armor plates
-found in outer layer
-3% organic matter
-no internal cells – dead tissue
Dermal scales and derivitives
-ostracoderm armor
-cosmoid scales
4 layers
-lamellar bone
-vascular or spongy bone
-dentine
-enamal
-strucutre is similar to bony elements in living
vertebrates
Evolution of bone
-degradation and loss of superficial layers
ganoid scales
elasmoid scales, bone than thin glaze of
enamel
Progressive loss of deep layers
-denticles
-teeth
On hard structures that have evolved from bony
scales
-osteodermsi n under the horny scutes of
crocodilians and other reptiles
-membrane bones
-fin rays of bony fish
SUPERCLASS GNATHOSTOMES (jawed fish)
4 clades of gnathostomes present
-placoderm
-acanthodii
-chondricthyes
-osteithyes
Placoderms (plate skin)
-all extinct
-benthic , bodies dorsal – ventrally flattened
-jaws but no true teeth, no dentine/enamel
-paired appendages with girdle
-vertebrae with neural and hemal arches
-gas bladder
-heavy armor
-gap in bony plates allowed head articulation
-class placoderm diverges early
Acanthodii
-well developed cranium and vertebral column
-large notochord
-dorsal and anal fins numerous paired fins
-probably used for good locomotion
-fins had a stout spine with tissue flap
-fast swimming aggressive predators
-shark like teeth
-first group we talk about that has true teeth
-teeth lack enamel, just have dentine
Placoderm and acanthodian versus
ostracoderm
-jaws
-paired fins
-internal support (girdle)
-vertebrae
-spiracle valve in small intestine
-renal portal system
-oviducts and mesonephric ducts
-more complex reproduction system
-pancreas with endocrine and exocrine function
-evolution of spleen
Vertebrate skeleton
-Visceral skeleton = splandocranium
-gill arch, jaw, hyoid arch
ancestral condition supports gill
mesenchyme cells derived from neutral crest
Gill arch
-each gill arch consists of a series of
cartilanginous or bony elements
Somatic skeleton = vertebrae, ribs
Dermal skeleton = dermal bones, some bones
around girdle, bones around cranium
Jaws
-Jaws  teeth
-teeth  grasping objects, biting, grindings,
manipulation of objects, defence
new resources available
Evolution of jaws
-first gill arch is lost – incorporated into the
base of the cranium
-second gill arch becomes mandibular arch
(upper and lower jaw)
-greater support for the jaws
-jaws attatched to cranium
-hyomandibular
Jaw suspension
-changed and enhanced by different types of
jaw suspension
3 types
-amphistylic
-hyostylic
-autostylic
Amphistylic
-palatoquadrate attatched by ligaments to
cranium and the hyomandibular
-palatoquadrate is not fused to cranium
-fossil sharks, some living sharks, crossopterygii,
acanthodii
Hyostylic
-hyomandibular attatched to jaw and cranium
by ligaments
-derived condition in most living sharks and ray
finned fishes
-allow for grasping of prey
Autostylic
-palatoquadrate firmly associated with or fused
with chondocranium
-hyoid arch does not participate
-stronger bite, capability for cutting and
grinding
-allows organism to bite stronger harder
organisms
-lungfish, all tetrapods, placodermi, holocephali
(ratfish)
Advantages of Jaws
-manipulation of objects
-grasp objects more firmly
-teeth
-defence
-new food items and habitats
Lecture 7
Acanthodii and Placodermii
-three major adaptations
1.jaws
2.paired fins
3.vertebrate
Paired fins
-improved mobility and steering
-advantages of paired fins
-increased control of movement
-evading predators, catching prey
-increased S.A greatly improves maneuverability
–provide lift and allows descent
-convert forward thrust to other directions
-defense – some bony fish have poisonous
spines on paired fins
-visual communication – fighting fish
Origins of paired fins
-agnathans had spines or enlarged scales
-ostracoderm “fins” derived from dermal armor
; solidly attatched to body
-paired fins present in acanthodii and
placoderms
-acanthodii – 2 rows of spines with attatched
tissue flaps. Some had internal skeleton or
cartiledge
-Placoderms
-well developed pectoral fins
-some were narrow based (similar to sharks)
-internal skeleton made of cartiledge and
flexible fin rays)
-may have been adjustable (change angle of
attack)
Pitch, Yaw, Roll
Up and down, side to side, roll around
Fish use all fins to coordinate where they are in
the water column
-three major theories on origin of paired fins
1. gill arch hypothesis
2. fin-fold hypothesis
3. fin-spine hypothesis
Gill arch hypothesis
-fins arose from gill arches
X – appearance of posterior pelvic girdle
X – different embryological origin of girdle and
gill arches
Fin-Fold hypothesis
-fins arose within a paired continous fleshy fold
stiffened by endoskeletal rays
Fin spine hypothesis
-early acanthodian had a series of hollow spines
with fleshy membrane along trunk
-later acanthodians had weak fin rays in the
membrane of pectoral and pelvic fins only
-acanthodians lost all spines exept 2 pairs
containing fin rays
Vertebrae
-agnathans
-cambrian agnathans - notochord with
vertebral elements
-ostracoderm lack vertebrae but had notochord
and dermal armor
-lamprey had remnants of neural arches
-acanthodii and placoderms the beginning of
vertebrae present
-mesodermal in origins
-forms around the notochord and the nerve
column
-ancestral condition
Ancient sharks, acanthodii, placoderms
-derived condition
Notochord reduced to disk between
vertebrates
Advantages of vertebral column
-stronger and more flexible than notochord
-greater lateral movement
-prevents collapse during movement
-solid surface for muscle attatchment
-lighter body than ostracoderms
Lecture 8
Class Chondritchyes “cartilanginous fishes”
Subclass elasmobranchii
-2 extinct orders of early shark
-2 extant orders
-orders selachii – living sharks
-order batoidea – skates and rays
Subclass holocephali (ratfish)
-orders chimaeraformes
Characteristics of chrondrithyes
-no dermal bones, ancestor had some
-cartilaginous skeleton, made them faster,
greater control
-placoid scales, no more dermal armor
-teeth in replacement families
-series of gill openings (exept for holocephali)
-spiracle
-no lungs or air bladder
-Claspers
Evolution of chrondrithyes
-first elasmobranchii occurred in late Silurian
-shark teeth most common fossil in the world
-very similar to placoderms (ecology similar)
3 major radiation of elasmobronchii
-paleozoic
-early Mesozoic
-extant radiation (Triassic)
1.paleozoic
-stem “chondrithyes”
-amphistylic jaw suspension
-teeth had 3 cusps
-notochord is continuous
-neural arches
-vertebrate, primitive condition
-no pectoral girdle (2 pectoral fin not connected
together , not as strong/control)
-fin broadly attatched to body
-no claspers
2.Second radiation
-stem “elasmobranchii”
-carboniferous to late creataceous
-amphistylic jaw suspension –but jaw is more at
front of mouth modern mouth more ventral
-predatory type of teeth
-two type of teeth in mouth
-vertebrae, hemal arch added to caudal region
-no pectoral girdle
-narrow based fins
-claspers present in some –internal fert
3. Modern radiation
-triassic
-modern appearance in Jurassic
-many Jurassic and cretaceous genera extant
-hyostylic jaw suspension
-upper jaw attatched loosely to cranium by
ligaments
-articulation between jaw, cranium and
hyomandibular protrusable jaw
-teeth single gusp or flat crown
-notochord constricted to form disk
-full vertebrate
-pectoral girdle
-narrow based fins
-claspers –internal fertilization
During Jurassic splits into two groups
-selachii
-batoidea
Subclass holocephali
-order chimeraformes
-oviparious, comes to shallow water to lay eggs
-autostylic upper jaw is firmly attatched to skull
-no teeth, instead large paltes attatched to jaw
-single gill covering “operculum” different from
bony fish
-large fanlike pectoral fins, main locomotion
force
-claspers
EVOLUTIONARY TRENDS
Fairy tail principle
Everything comes in sets of 3
-placoderm had jaws, paired fins, vertebrate
-3 radiations of sharks
-3 taxa of chondrithyes
Red ridinghood principle
-better to eat you with
-link structure -> better predator
-jaws
-teeth
-improved mobility, speed
-changes to fins, girdles, armor
-imrpoved maneuverability, control
-improved foraging efficiency and greater
foraging opportunities
Lecture 9
Class osteitchyes
-subclass actinopterygii (ray finned fish)
Infraclass chrondrostei sturgeon, paddlefish
(ancestral type)
Infraclass neopterygii
-series holostei (gars, bowfins)
-series telostei (salmon, trout etc)
-subclass sarcopterygii
-order dipnoi (lungfish)
-order crossoptyrigii (coelacanth, lobe
finned fish)
Characteristics of osteithyes
-bony skeleton (most)(developed
skull,vertebrate)
-dermal bones, teeth attached to jaws
-fish scales
-cosmoid scales made of bone, dentine, enamel
similar to ostracoderm armor (in crossoptyrgii)
-ganoid scale made of bone, enamel (holostei)
-elasmoid scale made of bone and a very thin
layer of enamel (bone is demineralized)
(telostei)
-internal support of fines
-ray finned
-no fleshy base; fin rays come out
directly from side of body
-lobe finned
-appendages come out from body and
rays come from the appendages
-hyostylic jaw suspension (most)
-dipnoi – autostylic
-crossoptyrgii – amphistylic
-Caudal fin
-primitive forms hypercercal
-most homocercal
-diverticulum –lung or gas bladder
-for bouncy
Subclass actinoptyrgii
3 major groups
Infraclass chrondrostei
-sturgeon, paddle fish
-early forms abundant in Devonian to Permian
-hypercercal tail
-thick ganoid scales
-gas bladder
-number of fin rays is greater than the number
of radial bones
Series holostei
-gars, bowfins
-slightly hypercercal tail
-decrease in bony armor
-light ganoid scales; modern forms remnants
only around head
-number of fin rays equals number of radials =
more flexible
-gas bladder
-hyostylic
Series Teleostei
-salmons, trout
-homocercal tail (lobes same size)
-gas bladder well developed
-thin elasmoid scales
-many dermal bones –complex skull
-fins tucked close to body to reduce drag
-hyostylic jaw suspension
-7-8 bones in upper jaw; maxilla premaxilla
Trends in actinoptergyii
-reduction in amount of bone
-simplification of scales
-improvement in feeding merchanisms
-hypercercal  homocercal tail
Because gas bladder for bouncy, tail is for thrust
only
-number of finerays >number of radials
-increase flex and moveability in fins
Subclass sarcoptyregii fleshy finned fish
Order dipnoi (lung fish)
-early forms had 2 dorsal fins, more advanced
no dorsal fins
-fossil forms
-elongated bodies
-thick cosmoid scales
-hypercercal tail
-unconstructed notochord – went through
vertebrate
-amphistylic
Modern form
-unconstricted notochord
-decrease in ossification
-autostylic
-homocercal tail
-lungs with diverticulum
-aestivation
Order crossoptyergii
-early forms
-lobe fin with fin rays in lower part
-cosmoid scale
-autostylic suspensision
-notochord unconstructed
Modern form
-cosmoid scales
-autostylic amphistylic
-coelacanth
Devonian to Permian - chrondostei
-large number of fin rays compared to radicals
-hypercercal tail
-thick heavy ganoid scales
-triassic to cretaceous – holostei
-fewer rays
-symmetrical tail
-reduction in scale size
-creataceous to modern – telostei
-homocercal tail
-thin elasmoid scales
-many feeding adaptations
-sarcopterygii- fleshy finned forms gave rise to
tetrapods
Life in water
-locomotion in water provides
1. access to a variety of habits
2. food in various habitats
3. escape from predators or unfavorable
conditions
Swimmers (fish) must:
1. reduce their resistance
2. have some means of propulsion/thrust
3. have control of movements
1. resistance
-resistance = drag
-two types of resistance
-viscious drag
-inertial drag
Viscious drag
-boundary layer – layers of water move pass
each other
-creates shearing force
-eddies crafted in boundary layer
-number of edits depend upon shape, texture of
surface, speed, rought skin, weird shape also
creates drag
Inertial drag
-formed as fish moves through water, it creates
a vaccume which displaces water
-water flows into replace this displaced water
and creates inertial drag
-shape and speed of fish affects the amount of
inertial drag
1. Resistance
-Adaptations to body form to reduce drag
Vdrag
I drag
Long thin
high
low
Short Fat
low
high
Intermediate good
good  most
efficient shape for swimming in water
2. Propulsion
-radial fins, aspect ratio = height/width
Higher aspect = higher speed
-undulation of body
-anguilliform body moving with tail
-carangiform
-ostraciformjust wiggle tail
Fins.
-use pectoral fins instead of caudal fins
(mantas)
3. Control of movement
-stability, breaking and steering
A) Stability
-body can move in several directions
Maintain stability
-fin plumment, relative density of lungs, shape
of head, gas bladder, lungs
Streamline head = more stability
B) Steer
-creating drag on one side (pulling one fin)
C) Break
-stick fins out on both side to create drag
Respiration in fish
-all living animals require oxygen
-move across cell boundaries by diffusion
-diffusion is too slow
Gills
-large S.A for diffusion Gill ->primary/secondary
lamallel
-elaborate design of gills and filaments
-support structure, structural support and
sepration of specialized tissue
-short diffusion distances, one cell sperating cel
from water
-water and blood flow counter current stream
-pumping mechanism to move water over gill
-Development of opercular pump that increases
flow of water over gills
Fishes have two types of pump
-buccal
-opercular pump
-Spiracle is lost
-losing spiracle makes opercular complex more
efficient
A. Buccal pump
-pressure pump
-opening mouth increase size of buccal cavity
-water pours into mouth
-closes mouth and raises floor of buccal cavity
-water forced over gills
Adaptation to increase gas exchange
-in some fish
1. buccal cavity highly vascularized
2. skin highly vascularized
3. diverticulum (pouch) off stomach or
esophagus
-acts as a receptacle for air and gas exchange
B. Opercular pump
-operculum – bone and associated tissues that
cover gills with one large plate
-lowering the floor of the buccal cavity, opens
mouth
-water flows into the cavity
- close mouth and push water over gills
-operculum pushed sideways with creates
suction and pulls last of the water out
-more efficient
RAM ventilation
-uses ocean current to get oxygen
-some sharks have this kind of breathing
Evolution of gills
-reduction of the number of gill arches
8 lamprey, 5 (4+1) sharks, 4 telostei
-interbranchail semptum is reduced
-reduced in sturgeon and even more in trout
compared to shark
-gain more SA to water
-Gill rays become divided into two elements to
support the gills additional SA
How did the diverticulum evolve?
-las gill pouch didn’t break the skin to forma gill
slit
-could hold air
-highly vascularized (gill tissue) can be oxygen
exchange  diffusion of oxygen
Lungs and Gas bladder
-early osteithyes evolved a diverticulum to
assist in buoyancy
-gas bladder evolution coupled with changes to
caudal fin and pectoral fin to increase mobility
Some fish under selective pressure uses gas
bladder as a source of oxygen
Characteristics of osteichthyes
-crossoptyergii
-early forms had lungs
-gas bladder arising from esophagus
-large amounts of fat associated with gas
bladder
-function in bouncy
Dipnoi
-early and modern forms had lungs
-lunges divided into many chambers
-many chanbers increase SA to increase gas
exchange
-air pushed into lungs by closing mouth or
diving
-air expelled by opening pharynx
-same physical action used to vent water of the
gills with the buccal pump
-first tetrapods used a similar system
Actinopterygii
-early forms had lung like structures
-modern forms have gas bladder off esophagus
-functions as hydrostatic organ – bouncy
-gas bladder most often attatched to esophagus
by dorsal pneumatic duct
 lungfish attatched ventrally