Comparative Vertebrate Anatomy

comparison of the vertabrates through lineage, and the types of eggs

1. Comparative Comparative
Vertebrate AnatomyVertebrate Anatomy
Chordate Origins & PhylogenyChordate Origins & Phylogeny
Presented by: Geonyzl Lepiten

2. Comparative vertebrate anatomy - the Comparative vertebrate anatomy - the
study of structure, of the function of study of structure, of the function of
structure, & of the range of variation in structure, & of the range of variation in
structure & function among vertebrates: structure & function among vertebrates:
Kingdom: Kingdom: Animal Animal
Phylum:Phylum: Chordata Chordata
Subphylum:Subphylum: Vertebrata Vertebrata

3. Vertebrate characteristics:Vertebrate characteristics:
1 - notochord (at least 1 - notochord (at least
in the embryo) in the embryo)
2 - pharynx with 2 - pharynx with
pouches or slits in pouches or slits in
wall (at least in the wall (at least in the
embryo) embryo)
3 - dorsal, hollow 3 - dorsal, hollow
nervous system nervous system
4 - vertebral column4 - vertebral column

4. NotochordNotochord = rod of living cells ventral to = rod of living cells ventral to
central nervous system & dorsal to central nervous system & dorsal to
alimentary canal alimentary canal
Fate of notochord during development: Fate of notochord during development:
Head region - incorporated into floor of Head region - incorporated into floor of
skull skull
Trunk & tail - surrounded by cartilaginous Trunk & tail - surrounded by cartilaginous
or bony vertebrate (except in Agnathans) or bony vertebrate (except in Agnathans)

5. Adults: Adults:
Fishes & amphibians - notochord persists the Fishes & amphibians - notochord persists the
length of the trunk & tail but is constricted length of the trunk & tail but is constricted
within the centrum of each vertebra within the centrum of each vertebra
Reptiles, birds, & mammals - notochord almost Reptiles, birds, & mammals - notochord almost
disappears during development (e.g., remains as disappears during development (e.g., remains as
a pulpy nucleus in the vertebrae of mammals) a pulpy nucleus in the vertebrae of mammals)
Protochordates - notochord remains as the chief Protochordates - notochord remains as the chief
axial skeleton axial skeleton
Agnathans - Agnathans - lateral neural cartilageslateral neural cartilages are located are located
on notochord lateral to the spinal cord on notochord lateral to the spinal cord

6. PharynxPharynx - region of alimentary canal - region of alimentary canal
exhibiting pharyngeal pouches in embryo; exhibiting pharyngeal pouches in embryo;
pouches may open to the exterior as pouches may open to the exterior as slitsslits::
 permanent slits - adults that live in water permanent slits - adults that live in water
& breathe via gills & breathe via gills
temporary slits - adults live on land temporary slits - adults live on land

7. Dorsal, hollow central nervous system - consists Dorsal, hollow central nervous system - consists
of brain & of brain & spinal cordspinal cord & contains a central cavity & contains a central cavity
(called the neurocoel) (called the neurocoel)

8. Vertebrate beginningsVertebrate beginnings

9. Among the oldest & best known Among the oldest & best known
= = ostracodermsostracoderms
fishes that occurred in the late Cambrian period fishes that occurred in the late Cambrian period
(see (see The Cambrian ExplosionThe Cambrian Explosion) through the ) through the
Devonian (about 400 - 525 million years before Devonian (about 400 - 525 million years before
present) present)
had bony plates and scales (&, therefore, were had bony plates and scales (&, therefore, were
easily fossilized) easily fossilized)
jawless vertebrates called 'armored fishes' jawless vertebrates called 'armored fishes'

10. Before ostracoderms? Before ostracoderms?
MyllokunmingiaMyllokunmingia fengjiaoafengjiaoa (pictured below) & (pictured below) &
HaikouichthysHaikouichthys ercaicunensisercaicunensis - primitive fish that - primitive fish that
have many similarities to living hagfishes and have many similarities to living hagfishes and
are the oldest vertebrates (530 mybf) ever are the oldest vertebrates (530 mybf) ever
found. found.

11. Before Vertebrates? Before Vertebrates?
CathaymyrusCathaymyrus diadexusdiadexus (literally the (literally the
'Chinese eel of good fortune') 'Chinese eel of good fortune')
= is not the fossil of an eel. At just 5 cm = is not the fossil of an eel. At just 5 cm
long, but 535 m.y. old, it is the earliest long, but 535 m.y. old, it is the earliest
known chordate. known chordate.
= Researchers think that = Researchers think that CathaymyrusCathaymyrus is a is a
fossil relative of modern lancelets fossil relative of modern lancelets
(amphioxus). (amphioxus).

12. CathaymyrusCathaymyrus

13. Phylum Phylum ChordataChordata - established in 1874 - established in 1874
& included organisms with: & included organisms with:
1 - notochord 1 - notochord
2 - pharyngeal pouches or slits 2 - pharyngeal pouches or slits
3 - dorsal, hollow nervous system 3 - dorsal, hollow nervous system
4 - cells that produce the hormone 4 - cells that produce the hormone
thyroxine thyroxine

14. Subphylum Subphylum UrochordataUrochordata = = tunicatestunicates
Chordate 'ancestor' of vertebrates: Chordate 'ancestor' of vertebrates:
sessile (like adult tunicates) sessile (like adult tunicates)
tail evolved as adaptation in tail evolved as adaptation in
larvae to increase mobility larvae to increase mobility
'higher forms' - came about by 'higher forms' - came about by
retention of tail (neoteny) retention of tail (neoteny)
Tunicate larva - also called 'sea squirt' Tunicate larva - also called 'sea squirt'
notochord is confined to the tail notochord is confined to the tail
notochord is lost during metamorphosis notochord is lost during metamorphosis
into sessile adult into sessile adult
possess pharyngeal slits possess pharyngeal slits

15. Tunicate anatomy Larval stage of the
tunicate

16. Subphylum Subphylum CephalochordataCephalochordata= =
Amphioxus (or Branchiostoma) Amphioxus (or Branchiostoma)
Vertebrate featuresVertebrate features: :
notochord notochord
dorsal, hollow nervous system dorsal, hollow nervous system
pharyngeal gill slits pharyngeal gill slits
'circulatory' system - vertebrate pattern with 'circulatory' system - vertebrate pattern with
'pumping vessels' (but no heart) 'pumping vessels' (but no heart)

17. Hemichordates Hemichordates = acorn worms = acorn worms
Bateson added acorn worms to the Bateson added acorn worms to the
phylum Chordata in 1884 because phylum Chordata in 1884 because
they have: they have:
1 - a dorsal, hollow nervous system 1 - a dorsal, hollow nervous system
2 - gill slits 2 - gill slits
3 - a short diverticulum of the gut 3 - a short diverticulum of the gut
called the stomochordcalled the stomochord
Present consensus = the stomochord is Present consensus = the stomochord is
not homologous with the notochord not homologous with the notochord
and Hemichordates are placed in a and Hemichordates are placed in a
separate phylum separate phylum

18. Possible invertebrate ancestors: Possible invertebrate ancestors:
1 - 1 - annelid wormsannelid worms

Evidence for:Evidence for:
–bilateral symmetry bilateral symmetry
–segmented segmented
–central nervous system with brain central nervous system with brain
& longitudinal nerve cord& longitudinal nerve cord
Evidence against:Evidence against:
–nerve cord is solid nerve cord is solid
–nerve cord is ventral nerve cord is ventral

19. 2 - 2 - echinodermataechinodermata - chordate - chordate
characteristics include:characteristics include:
–radial cleavage - blastomeres in adjacent tiers radial cleavage - blastomeres in adjacent tiers
lie directly above one another (as opposed to lie directly above one another (as opposed to
spiral cleavage) spiral cleavage)
–anus forms near or at blastopore anus forms near or at blastopore
(deuterostomous) (deuterostomous)
–mesoderm arises as outpocketing of the gut mesoderm arises as outpocketing of the gut
wall wall
–indeterminate cleavage (i.e., fate of indeterminate cleavage (i.e., fate of
blastomeres isn't predetermined) blastomeres isn't predetermined)

20. Phylum: Phylum: ChordataChordata
Subphylum: Vertebrata Subphylum: Vertebrata
Superclass: Superclass: PiscesPisces
Class Class AgnathaAgnatha
Class Class PlacodermiiPlacodermii
Class Class ChondricthyesChondricthyes
Class Acanthodii Class Acanthodii
Class Class OsteichthyesOsteichthyes
Superclass: Tetrapoda Superclass: Tetrapoda
Class Class AmphibiaAmphibia
Class Class ReptiliaReptilia
Class Class AvesAves
Class Class MammaliaMammalia

21. Agnathans vs. Gnathostomes:Agnathans vs. Gnathostomes:
semicircular canals semicircular canals
–agnathans have 1 or 2 agnathans have 1 or 2
–gnathostomes have 3 gnathostomes have 3
jointed, paired lateral appendages jointed, paired lateral appendages
–agnathansagnathans have none have none
–gnathostomes do gnathostomes do
jaws jaws
–agnathans have none agnathans have none
–gnathostomes do gnathostomes do

22. Class AgnathaClass Agnatha
Orders: Orders:
1 - 1 - OsteostraciOsteostraci 2 - Anaspida 2 - Anaspida
3 - 3 - ThelodontiThelodonti
4 - 4 - GaleaspidaGaleaspida
5 - 5 - PituriaspidaPituriaspida
6 - Petromyzontia (lampreys) 6 - Petromyzontia (lampreys)
7 - Myxinoidea (hagfishes)7 - Myxinoidea (hagfishes)

23. Ostracoderms (Osteostraci, Anaspida, Ostracoderms (Osteostraci, Anaspida,
Heterostraci, & Coelolepid): Heterostraci, & Coelolepid):
1 - extinct Paleozoic (Cambrian to Devonian) 1 - extinct Paleozoic (Cambrian to Devonian)
jawless fish with an external skeleton of bone jawless fish with an external skeleton of bone
('bony armor') ('bony armor')
2 - oldest known vertebrates 2 - oldest known vertebrates
3 - many had flattened appearance (some 3 - many had flattened appearance (some
may have been bottom-dwellers)may have been bottom-dwellers)

24. CyclostomesCyclostomes (Petromyzontia & Myxinoidea): (Petromyzontia & Myxinoidea):
LampreysLampreys - parasitic with horny, rasping teeth - parasitic with horny, rasping teeth
(see drawing at right) (see drawing at right) HagfishesHagfishes - primarily - primarily
scavengersscavengers

25. GnathostomesGnathostomes
Acanthodians:Acanthodians:
1 - earliest known gnathostomes (1 - earliest known gnathostomes (SilurianSilurian; ;
about 440 mybp) about 440 mybp)
2 - 2 - probablyprobably related to modern bony fishes related to modern bony fishes
3 - small (less than 20 cm long) with large 3 - small (less than 20 cm long) with large
eyes eyes
4 - 4 - AcanthodiansAcanthodians most likely died out most likely died out
because of the rapidly increasing number because of the rapidly increasing number
of ray-finned fishes and sharks during the of ray-finned fishes and sharks during the
PermianPermian

26. Class Class PlacodermiiPlacodermii::
1 - Silurian (about 420 million years before 1 - Silurian (about 420 million years before
present) 2 - probably off the main line of present) 2 - probably off the main line of
vertebrate evolution vertebrate evolution
3 - many had bony dermal shields 3 - many had bony dermal shields
4 - some were probably predators (with 4 - some were probably predators (with
large, sharp 'tooth plates')large, sharp 'tooth plates')

27. Vertebrate EggsVertebrate Eggs

28. Types EggsTypes Eggs
A.A.Alecithal = Eggs with little yolkAlecithal = Eggs with little yolk
ex. Amphioxus eggex. Amphioxus egg
b. Mesolecithal = eggs with moderate b. Mesolecithal = eggs with moderate
amount of yolkamount of yolk
ex. Freshwater lampreys ex. Freshwater lampreys
ganoid fishesganoid fishes
lungfishes lungfishes
amphibians amphibians

29. C. Megalecithal = massive amount of yolkC. Megalecithal = massive amount of yolk
ex. Monotremesex. Monotremes
marine lampreysmarine lampreys
teleostteleost
reptiles reptiles
birdsbirds

30. Types of distribution of yolkTypes of distribution of yolk
a.a.Isolecithal = even distribution of yolkIsolecithal = even distribution of yolk
present in alecithal eggspresent in alecithal eggs
b. Telolecithal = the cytoplasm and yolk b. Telolecithal = the cytoplasm and yolk
tends to concentrate or accumulate at tends to concentrate or accumulate at
the oposite poles.the oposite poles.
present in mesolecithal eggs present in mesolecithal eggs
and in megalecithal eggsand in megalecithal eggs

31. Oviparity and ViviparityOviparity and Viviparity
viviparyvivipary: the embryo develops inside the body : the embryo develops inside the body
of the mother and living young is deliveredof the mother and living young is delivered
: reared by the mother.: reared by the mother.
: but the eggs of viviparous animals : but the eggs of viviparous animals
lack a hard outer covering or shell like the lack a hard outer covering or shell like the
chicken egg. chicken egg.
:Viviparous young grow in the adult :Viviparous young grow in the adult
female until they are able to survive on their female until they are able to survive on their
own outside her body. own outside her body.

32. :developing fetuses of viviparous :developing fetuses of viviparous
animals are connected to a animals are connected to a placentaplacenta in the in the
mother's body mother's body
Egg-laying, or Egg-laying, or oviparousoviparous, animals obtain , animals obtain
all nourishment as they develop from the all nourishment as they develop from the
yolk and the protein-rich albumen, or yolk and the protein-rich albumen, or
"white," in the egg itself, not from direct "white," in the egg itself, not from direct
contact with the mother, as is the case contact with the mother, as is the case
with viviparous young. with viviparous young.
: expulsion of undeveloped eggs : expulsion of undeveloped eggs
rather than live young. rather than live young.

33. ovoviviparityovoviviparity : :animalsanimals develop within develop within
eggseggs that remain within the mother's body that remain within the mother's body
up until they hatch or are about to hatch up until they hatch or are about to hatch
: employed by many : employed by many
aquatic life forms such as aquatic life forms such as fishfish and some and some
sharkssharks, , reptilesreptiles, and , and invertebratesinvertebrates. The . The
young of ovoviviparous young of ovoviviparous amphibiansamphibians are are
sometimes born as sometimes born as larvaelarvae, and undergo , and undergo
metamorphosismetamorphosis outside the body of the outside the body of the
mother.mother.

34. In fertilization:In fertilization:
Gametes are essential in fertilizing the Gametes are essential in fertilizing the
eggseggs
- sperm which came from the male- sperm which came from the male
- ovum from the females- ovum from the females
 when the female and male gametes when the female and male gametes
unite it will form into zygote.unite it will form into zygote.

35. CleavageCleavage
The fertilized egg (zygote) is The fertilized egg (zygote) is
transformed by cell division transformed by cell division
(cleavage) into a mutlicellular cells (cleavage) into a mutlicellular cells
called called BlastulaBlastula
During cleavage the individual cells During cleavage the individual cells
are called are called blastomereblastomere
The blastula is a hollow ball of cells The blastula is a hollow ball of cells
with a cavity is called with a cavity is called blastocoelblastocoel

38. In microlecithal eggs like In microlecithal eggs like
in amphioxus have total in amphioxus have total
or holoblastic cleavage or holoblastic cleavage
(the cleavage furrows (the cleavage furrows
the entire yolk)the entire yolk)
Divided equallyDivided equally
The resultant blastula is The resultant blastula is
a hollow ball of cells with a hollow ball of cells with
a cavity called a cavity called
blastocoelblastocoel

39. In mesolecithal egg like in In mesolecithal egg like in
frog have a total but frog have a total but
unequal cleavageunequal cleavage
Blastomere near the Blastomere near the
vegetal pole are larger vegetal pole are larger
than those in the animal than those in the animal
pole.pole.
Development is slowDevelopment is slow
The blastocoel is The blastocoel is
displaced on the animal displaced on the animal
hemisphere.hemisphere.

41. Macrolecithal egg have unequal Macrolecithal egg have unequal
and partial or meroblastic cleavageand partial or meroblastic cleavage
Limited to the relatively small yolk-Limited to the relatively small yolk-
free region at the animal polefree region at the animal pole
Yolk mass is to great to be Yolk mass is to great to be
penetrately by the cleavage penetrately by the cleavage
furrowsfurrows
A cellular blastoderm is separated A cellular blastoderm is separated
from the uncleaved yolk by a from the uncleaved yolk by a
narrow cavitynarrow cavity

42. Fish blastula

43. GrastulaGrastula

44. GastrulaGastrula
When the blastula developed into an embryoWhen the blastula developed into an embryo
= at first the gastrula has two germ layer = at first the gastrula has two germ layer
(ectoderm and endoderm)(ectoderm and endoderm)
= and then later to three germ layers = and then later to three germ layers
(ectoderm, mesoderm and endoderm)(ectoderm, mesoderm and endoderm)
Gastrulation of a
diploblast: The
formation of germ layers
from a (1) blastula to a (2)
gastrula. Some of the
ectoderm cells (orange)
move inward forming the
endoderm (red).

45. Neurulation and Neural CrestNeurulation and Neural Crest
Neurulation Neurulation is a process to convert the gastrula is a process to convert the gastrula
into into neurulaneurula..
is a part of is a part of organogenesisorganogenesis in in vertebratevertebrate embryosembryos
Steps of neurulation include the formation of the Steps of neurulation include the formation of the
dorsal nerve corddorsal nerve cord, and the eventual formation of , and the eventual formation of
the central nervous system. the central nervous system.
The process begins when the The process begins when the notochordnotochord induces induces
the formation of the the formation of the central nervous systemcentral nervous system
(CNS) by signaling the ectoderm (CNS) by signaling the ectoderm germ layergerm layer
above it to form the thick and flat above it to form the thick and flat neural plateneural plate

46. The neural plate folds in upon itself to form the The neural plate folds in upon itself to form the
neural tubeneural tube, which will later differentiate into the , which will later differentiate into the
spinal cordspinal cord and the and the brainbrain, eventually forming the , eventually forming the
central nervous system. central nervous system.

47. Neurulation in vertebrates results in the Neurulation in vertebrates results in the
formation of the formation of the neural tubeneural tube, which gives , which gives
rise to both the spinal cord and the brain. rise to both the spinal cord and the brain.
Neural crest cellsNeural crest cells are also created are also created
during neurulation. Neural crest cells during neurulation. Neural crest cells
migrate away from the neural tube and migrate away from the neural tube and
give rise to a variety of cell types, give rise to a variety of cell types,
including pigment cells and neurons. including pigment cells and neurons.

48. 1. Neurulation begins with the formation of a 1. Neurulation begins with the formation of a
neural plateneural plate, a thickening of the ectoderm , a thickening of the ectoderm
caused when cuboidal epithelial cells become caused when cuboidal epithelial cells become
columnar. columnar.
2. Changes in cell shape and cell adhesion cause 2. Changes in cell shape and cell adhesion cause
the edges of the plate fold and rise, meeting in the edges of the plate fold and rise, meeting in
the midline to form a the midline to form a tubetube..
3. The cells at the tips of the 3. The cells at the tips of the neural foldsneural folds come come
to lie between the to lie between the neural tubeneural tube and the and the
overlying overlying epidermisepidermis. .
4. These cells become the 4. These cells become the neural crest cellsneural crest cells. .
Both Both epidermisepidermis and and neural plateneural plate are capable are capable
of giving rise to of giving rise to neural crest cellsneural crest cells. .

51. OrganogenesisOrganogenesis
Organogenesis is the period of animal Organogenesis is the period of animal
development during which the embryo is development during which the embryo is
becoming a fully functional organism capable of becoming a fully functional organism capable of
independent survivial. independent survivial.
process by which specific organs and process by which specific organs and
structures are formedstructures are formed, ,
and involves both and involves both cell movementscell movements and and cell cell
differentiationdifferentiation. .
Organogenesis requires interactions between Organogenesis requires interactions between
different tissues. These are often different tissues. These are often reciprocalreciprocal
interactions between interactions between epithelial sheetsepithelial sheets and and
mesenchymal cellsmesenchymal cells. .

54. The endoderm produces tissue within the lungs, thyroid, and
pancreas. The mesoderm aids in the production of
cardiac muscle, skeletal muscle, smooth muscle, tissues
within the kidneys, and red blood cells. The ectoderm
produces tissues within the epidermis and aids in the
formation of neurons within the brain, and melanocytes.

55. Organogenesis from EctodermOrganogenesis from Ectoderm
1. 1. From Somatic EctodermFrom Somatic Ectoderm
- epidermis of skin- epidermis of skin
- enamel- enamel
- Stomodeum (mouth)- Stomodeum (mouth)
- Proctodeum (cloaca or anus )- Proctodeum (cloaca or anus )
- Gill Epithelium- Gill Epithelium
- Amnion and Chorion (in part) - Amnion and Chorion (in part)

56. 2. Neural Plate ectoderm2. Neural Plate ectoderm
- Brain and Spinal Cord- Brain and Spinal Cord
3. Epidermal Placodes3. Epidermal Placodes
- Olfactory capsules- Olfactory capsules
- Optic capsule- Optic capsule
- Otic Capsule- Otic Capsule
- Epibranchial capsule- Epibranchial capsule
- Electroreceptors/ neuromsst organs- Electroreceptors/ neuromsst organs
- ganglia of some cranial nerves - ganglia of some cranial nerves

57. 4. Neural Crest4. Neural Crest
- Spinal Ganglia- Spinal Ganglia
- Splanchnocranium- Splanchnocranium
- Neurocranium- Neurocranium
- Dermatocranium- Dermatocranium
- Dentine- Dentine
- Cornea- Cornea
- Chromatophores- Chromatophores
- Branchiomeric muscles- Branchiomeric muscles
- aortic arches- aortic arches
- heart septa - heart septa

58. Organogenesis From the Organogenesis From the
mesodermmesoderm
1.1.Epimere (dermatome) – DermisEpimere (dermatome) – Dermis
2.2.Epimere (myotome) – Axial MuscleEpimere (myotome) – Axial Muscle
- Appendicular Muscle- Appendicular Muscle
- Branchiomeric Muscle- Branchiomeric Muscle
- Hypobranchial - Hypobranchial
3. Epimere (sclerotome) – Vertebrae3. Epimere (sclerotome) – Vertebrae
4. Chordamesoderm – notochord4. Chordamesoderm – notochord

59. 5. Intermediate mesoderm (Mesomere)5. Intermediate mesoderm (Mesomere)
-kidney and Urogenital ducts-kidney and Urogenital ducts
6. Somatic hypomere = 6. Somatic hypomere =
- ribs- ribs - Parietal peritoneum- Parietal peritoneum
- Sternum - Sternum - Genital Ridge- Genital Ridge
- appendicular skeleton- appendicular skeleton
- appendicular muscle - appendicular muscle
- amnion and chorion- amnion and chorion

60. 7. Splanchnic hypomere7. Splanchnic hypomere
- Blood - Blood
- heart- heart
- gut- gut
- smooth muscle- smooth muscle
- visceral peritoneum- visceral peritoneum
- yolk sac and allantois- yolk sac and allantois

61. Organogenesis of the EndodermOrganogenesis of the Endoderm
1. Foregut – Oral Cavity1. Foregut – Oral Cavity - Gill Epithelium - Gill Epithelium
- nasal cavity - Lung epithelium- nasal cavity - Lung epithelium
- Pharynx epithelium- Pharynx epithelium
2. Midgut - Stomach2. Midgut - Stomach - Liver - Liver
- Bladder- Bladder - Pancreas - Pancreas
- intestines- intestines - Allantois - Allantois
- germ cells of gonads - germ cells of gonads
- yolk sac membrane - yolk sac membrane
3. Hindgut – Urinary Bladder and Cloaca or anus3. Hindgut – Urinary Bladder and Cloaca or anus

62. The End of the ChapterThe End of the Chapter