3. Phylum
Chordata
Animals with a Notochord:
ANotochord which is an elastic, solid sheathed (covered)
supporting rod present on the dorsal side between the nerve chord
and the gut.
It is present either in the embryonic stage only or throughout the
life.
In higher chordates, it gives rise to the axial endoskeleton of
cranium andvertebral column.
Ahollow tubular nerve chord is present mid-dorsally above the
notochord.
Pharyngeal gill slit are paired apertures (opening) present on the
lateral sides of the Pharynx to outside. They take part in respiration as
well as feeding.
In fishes and some amphibians they remain functional throughout life.
In other chordates they occur only in the embryonic stage.
Apost anal tail occurs in most chordates at least in the embryonic
stage.
In majority of chordates, it helps in balancing it also provides
protection to the genital and anal region.
4. They are bilaterally symmetrical, triploblastic
Eucoelomates with ‘tube-within-tube’ bodyplan.
They have well developed Digestive System,
Respiratory system, Circulatory system, Excretory
system andNervous system.
Asexual reproduction is absent. Sexes are separate,
Dioecious.
Phylum Chordata is divided into 3 sub phyla:
1.Urochordata,
2. Cephalochordata,
3. Vertebrata.
5. Sub-phylum:
Urochordata
Sub Phylum –Urochordata:
Notochord is present only in tail of larva.
CNS is lost during metamorphosis.
Body is covered by a leathery test or Tunic formed
of Tunicin, so called Tunicates.
There are numerous gill slits or stigmata on the
lateral walls of pharynx.
Stigmata open into an ectodermal-lined cavity called
Atrium.
They are marine, mostly sedentary and filter
feeders.
E.g. Ascidia, Salpa, Doliolum
7. Sub-phylum:
Cephalochordata
Sub- Phylum Cephalochordata:
Notochord extends from anterior end to posterior
end of body. Notochord persists throughout life.
CNS is present but not differentiated into brain
and spinal cord.
Pharynx has numerous gill slits so called Branchial
basket.
Tail is present throughout life.
E.g. Branchiostoma (Amphioxus or Lancelet).
12. Sub-phylum:
Vertebrata
They possess a notochord only during the embryonic stage.
It is replaced by a bony or cartilaginous vertebral column in
the adults. (All vertebrates are chordates but all chordates are
not vertebrates)
Besides the basic chordate characters, they also possess other
characters such as:
1. Aventral muscular heart with two, three or four chambers.
2. Paired appendages arepresent.
3. Exo-skeleton as well as endo-skeleton are present.
4. They have well developed respiratory system, which
consists of either gills, lungs or skin.
5. Presence of portal systems namely Hepatic portal system,
Renal portal system, Hypophyseal portal system.
13. Division: Agnatha
Class: Cyclostomata
This constitutes jawlessEcto-parasites.
They are marine animals found attached to the fishes.
The body is elongated with head, trunk and a
compressed tail.
Paired appendages are absent.
They have a circular, suctorial mouth without jaws.
The body is devoid of scales.
Their cranium and vertebral column are cartilaginous.
Respiration through 5 to 15pairs of gill slits.
Their intestine has a special structure called Typhlosole.
14. Circulatory system is closed type.
They are Poiklothermic (cold blooded ) animals.
They migrate to the fresh water for spawning (for
breeding, laying eggs) after which they die. The larvae
after metamorphosis return to the ocean.
They are Anadromous i.e. they migrate from sea to
the fresh water for breeding.
Sexes are separate with single gonads. Fertilization
external.
Development indirect. The larva iscalled
Ammocoete larva.
E.g. Petromyzon (Lamp ray)
Myxine (Hag fish).
15.
16. Division: Gnathostomata
Super Class: Pisces. Class: Chondrichthyes.
This group includes all Cartilagenous fishes such as
sharks, ray fishes and skates.
They are marinewith streamlined body.
Their endoskeleton is made up of cartilage and the
exoskeleton is made up of Placoid scales which make
the skinrough.
Mouth is ventral with Acrodont (teeth attached to jaw)
backwardly directed teeth. The jaws are very powerful.
Presence of two dorsal fins, the Caudal (tail) fin is
Heterocercal (uneven).
The intestine has Scroll or Spiral valve to increase the
surface area.
Respiration through gills. 5-7 pairs of gill slits are present
on the lateral sides of the head, which are not covered by
operculum.
18. Cloaca is a common aperture for both the digestive tract and
the reproductive tract.
Swim bladder or air bladder is absent. Hence they need to
swim all the time to prevent sinking.
Heart is two chambered and is called a venous heart (venous
blood- deoxygenated blood) (only venous blood flows through
the heart).
They have Single Circulation of blood.
Excretion by kidneys and they are Ureotelic (main excretory
product isurea).
They are Dioecious, fertilization internal.
Females are Viviparous or Ovoviviparous. Development is
direct.
They are Poikilothermic (cold blooded) or Ectothermic.
E.g. Scoliodon (Sharks) (Dog fish), Chimaera (Rabbit fish)
(Fossil fish) , Pristis (sawfish), Sphyrna (Hammer headed
shark), Trygon (sting ray), Torpedo (ElectricRay), Rhinobatus
(Guitar fish).
20. Super Class: Pisces, Class: Osteichthyes
This group includes marine as well as freshwater fishes.
The endoskeleton is made up of bones.
Mouth is terminal or sub-terminal.
Dorsal fin is single, the Caudal fin is Homocercal.
The body is covered with exoskeleton made up of scales which may
be Cycloid, Ctenoid and Genoid scales.
The skin is smooth or slimy due to presence of mucus.
4 pairs of gills are present on bony gill arches covered by
Operculum on the lateral sides of the head. Fishes are coldblooded.
(Poikilothermic).
The external nostrils are only olfactory (detect smell) in function.
Heart is two chambered and venous.
Excretion by kidneys and are Ureotelic and very few are
Ammonotelic.
Air bladder or swim bladder is present which helps in maintaining
buoyancy.
They are Dioecious females are oviparous, fertilization external,
development direct.
E.g. Labeo, Chana, Catla, Hilsa, Anabas (climbing perch),
Hippocampus,(sea horse), Exocoetus (flying fish), Protopterus(lung
afish).
24. CHARACTER CARTILAGE FISHES BONY FISHES
1. Habitat Always marine Marine and Freshwater
2. Exoskeleton Placoid scales Cycloid, Genoid or
Ctenoid scales
3. Endoskeleton Completely Cartilagenous Mainly bony
4. Mouth Ventral Terminal
5. Gut opening Cloacal aperture Anus
6. Intestine Has Scrollvalve Scroll valveabsent
7. Gill slits 5 _ 7 pairs, not coveredby
Operculum
4 pairs, coveredby
Operculum
8. Swim Bladder Absent Present
9. Excretion Ureotelism Ammonotelism
10. Caudal Fin Heterocercal Mostly Homocercal
11.Dorsal Fin Two in number Single
12. Claspers Present Absent
25. Super Class: Tetrapoda, Class: Amphibia
Amphibians occur in both freshwaters and moist terrestrial
waters. Afew of them are arboreal (tree living) {e.g. Hyla
(tree frog}.
Body is divisible into head, trunk and limbs.
Fins are present in the larval stages but not paired.
They have 2 pairs ofPentadectyl limbs, however, claws are
absent. Limbs are absent in limbless amphibians called
Apoda e.g. (Ichthyophis) (looks like eel).
Skin is smooth, devoid of any Exoskeletal structures. It is
richly supplied with blood capillaries. The skin is shiny due to
presence of mucus glands.
Chromatophores (structured with coloured pigment) are often
present in the skin.
Endoskeleton is bony and cartilaginous.
The eyeshave eyelids. Athird eyelid called nictitating
membrane is present.
Alimentary canal, Urinary system and the Reproductive system
open into a chamber called cloacal chamber, which opens to
the exterior through an aperture called cloacal aperture.
26. Respiration through lungs in adults through skin during
hibernation (winter sleep) and aestivation (summer sleep).
Through gills in the larval stages (exception Nocturus (mud puppy)
respire through gills even in adult stage). Buccal epithelium also helps
in respiration.
Excretion through Kidney. The larval stages are Ammonotelic.
Adults are Ureotelic. Desert amphibians are Uricotelic.
Heart is 3 chambered. There is mixing up of arterial and venous
blood to some extent in the ventricle.
The Endocrine system and Nervous system are well developed.
Development is controlled by Thyroxin hormones.
Extra embryonic membranes are absent, so they are Anamniotes.
Sexes are separate, fertilization external, oviparous, development
is indirect involving the larval stage called Tadpole.
They are poikilothermic and they undergo Hibernation and
Aestivation.
E.g. Amphiuma, Ichthyophis, Salamandra, Hyla (tree frog),
Rana tigrina (frog), Bufo (toad), Pipa (midwife toad).
30. Super Class: Tetrapoda, Class:Reptilia
They are called Creeping vertebrates
These are the truly terrestrial animals.
They are found in all types of habitats.
They are Fossorial (dig burrows, holes) Cursorial, Arboreal,
Creepers etc.
Body is divisible into 4 parts – head, neck, trunk and tail. Two pairs
jointed limbs are present which are Pentadectyl, the digits end in
claws.
Snakes and some lizards have lost the limbs, skin is dry, rough
and horny with very few glands.
Exoskeleton consists of dry-epidermal scales, plates, shields,
Scutes etc.
The endoskeleton has ribs and Sternum (breast bone). A‘T’shaped
inter clavicleis present.
The exoskeleton is periodically shed off as a skin cast in many
reptiles.
The jaws contain teeth, however they are absent in turtles. They
have horny beaks like structures.
31. Alimentary canal opens into Cloaca.
The heart is 3 – chambered, but the ventricle is incompletely
divided. Crocodiles have 4-chambered heart.
Two portal systems are present.
RBCs are nucleated (have nucleus in RBCs).
They are Poikilothermic.
Respiration through lungs (pulmonary respiration). Cloacal
respiration occurs in turtles.
Excretion with the help of Kidneys. Urinary bladder is
absent in snakes.
The terrestrial forms are Uricotelic and aquatic forms are
Ureotelic.
Nervous system is well developed, sense organs are well
developed.
They are Dioecious. Fertilization Internal, they are Oviparous
and occasionally Ovo-viviparous.
The embryo is covered by 4 extra embryonic membranes
namely
(i) Chorion (ii) Allantois, (iii) Ammnion (iv) Yolksac
32. (Note: Reptiles, Birds and Mammals are said to be Amniotic animals due
to the presence of the extra embryonic membrane specially Amnion
with amniotic fluid)
1. Order –Squamata
a) Sub order: Lacertelia - includes lizards. (study of lizards is
called Saurology)
E.g. Hemidactylus (wall lizard), Calotes (Garden lizard),
Draco (flying lizard), Varanus (monitor lizard), Heloderma
(poisonous lizard), Chamaeleon.
b) Sub Order: Ophidia- includes snakes (study of snakes is
called Ophiology).
E.g. Naja naja (King Cobra), Bangarus (Krait), Vipera (Viper),
Hydrophis (poisonous sea snake) .
2. Order – Chelonia (Turtles and Tortoises)
E.g. Testudo (Tortoise), Chelone (Turtle).
3. Order – Crocodilia – includes Crocodiles, Gharial and Alligators.
(study of crocodiles: Herpetology).
E.g. Crocodilus, Gavialis (Gharial- very pointed snout),
Alligator (long snout).
37. Super Class: Tetrapoda, Class:Aves
They are found all over the world because of their ability to fly.
Body is spindleshaped (streamlined).
Head is round, the jaw bones are prolonged to form a beak which is
toothless.
The beak is covered with a horny sheath called Rhampothica
(Theca – covering).
Neck is flexible and is of variable, length.
The trunk is compact and tail is short.
Body has two pairs of jointed limbs- fore limbs and hind limbs. The
forelimbs are modified into wings. Hind limbs are used for
supporting the body, walking, swimming, wading, clasping etc.
Birds are therefore bipedal (two legs). The limbs commonly have 4
digits which end in claws.
Exoskeleton is made up of feathers, scales claws and sheath.
Scales are present on the legs. Body is covered with feathers. Feathers
are mainly of 3 types – Quill feathers, (a.k.a. flight feathers),
Contours (which cover the body), Filoplumes (in between quill
and contours) and Down feathers. (Reminges )– flight feathers
on the wings, Retrices – flight feathers on the tail).
38. At the base of the tail there is a small oil gland called
Preen gland used for dressing the feathers.
Endoskeleton consists of spongy or pneumatic (air
cavities, porous, spongy) bones, which make it their body
light.
Long bones are hollow with air cavities.
Sternum or breast bone is enlarged to form a Keel for the
attachment of wings. AWish bone (V-shaped)is formed
by the fusion of Clavicles.The tail vertebrae are fused to
form Pygostyle.
The digestive system contains extra structures. The
esophagus is enlarged to form Crop for storing and
softening the food. (The birds milk is the product of
crop). The stomach is divisible into two parts:
(a) Agrinding region called Gizzard.
(b) Aglandular region calledPro-ventriculous.
39. Respiration through lungs. The lungs are connected
with distensible air sacs. Larynx is called Syrinx in
birds.
Heart is 4 chambered, which separates the oxygenated
and deoxygenated blood.
Two portal systems present – Renal portal system is
reduced.
They are Homoeothermic or Endothermic with the
body temperaturearound 100o F.
Kidney is present. Urinary bladder is usually absent.
They are Uricotelic, Cloaca present.
The sense of sight is very well developed. Pinnae (ear
lobe) are absent. The sense of smell is poorly developed.
They are Dioecious (unisexual), fertilization internal,
females are oviparous.
The left ovary is only functional. (to make body light).
Development isdirect.
The embryo is covered by 4 extra embryonic
membranes. Hence theyare Amniotes.
40. Flightless Birds:
E.g. Struthio (Ostrich), Rhea, Apteryx(Kiwi),
Dromaias (Emu), Aptenodytes (Penguin).
Flight Birds:
E.g. Columba (Pigeon), Paser (Sparrow),Psittacula
(Parrot), Pavo (Peacock), Corvus (Crow),
Anas (duck), Tyto (Owl), Pseudogypes (Vulture),
Eudynamis (Koel – Indian Nightingale).
45. Super Class: Tetrapoda, Class:Mammalia
Found all over the earth. Body is divisible into head, neck,
trunk and tail. Tail is vestigial (of no use) in some mammals.
Presence of 2 pairs of jointed limbs modified for walking,
running,climbing, swimming, burrowing, flying etc.
Skin is many layered, the outer most layer is made up of
dead, Keratinized cells.
Sweat glands (Sudoriferous), oil glands (Sebaceous
glands) are present in the skin.
The mammary glands are modified sweat glands present
in both male and females, but are functional only in
females (after the birth of young ones).
Exoskeleton consists of hair, scales, spines, hooves,
claws, horns etc.
Endoskeleton made of bones and cartilage.
Coelom is divided into a Thoracic cavity and
Abdominal cavity by a muscular partition called
Diaphragm.
46. The neck vertebrae are 7 in number.
The teeth are Heterodont (dissimilar teeth),
Thecodont (teeth inside gums) and Diphyodont {2
sets of teeth (milk teeth &permanent)}.
The anal aperture, the urinogenital apertures are
separate (cloaca isabsent).
Pulmonary respiration (through lungs) trachea
(wind pipe) protected by epiglottis.
Heart is 4 chambered. RBCs are enucleated
(without nucleus) except Camel and Liama (double
horned Camel). Double circulation, two portal
systems present.
They are Homoeothermic or Endothermic.
Kidneys are Metanephric. Urinary bladder is
present.
47. Nervous system well developed, with 12pairs ofcranial
nerves. External ears (Pinnae)are present. Sense
organs are welldeveloped.
They are Dioecious, males have a copulatory organ
called penis.
Testes descend down into the scrotal sacs. Urinogenital
apertures is common in males, but the urinary apertures
and the genital apertures are separate in females.
They are Viviparous. Fertilization is internal.
Development isdirect.
The young one are nourished by the females through
milk secreted by the mammary glands.
Class Mammalia divided into3 sub-classes:
(i) Prototheria
(ii) Metatheria
(iii) Eutheria.
48. 1.Prototheria (primitive mammals):
External ears absent or rudimentary.
They form a connecting link between reptile and
higher mammals.
Cloaca present.
Testes abdominal
They are oviparous.
It includes only1order:
Order – Monotremata(egg laying mammals)
E.g. Ornithorinchus – (Duck billplatypus).
Echidna (Tachyglossus) Spiny ant eater.
50. 2. Metatheria (Pouched Mammals):
Metatheria includes Marsupial mammals where
the female develop a pouch called Marsupium. The
immature young ones are nourished in the
Marsupium.
Mammary glands and nipples present.
Anus and Urinogenital apertures are controlled by a
common sphincter.
E.g. Macropus (Kangaroo).
Didelphys (American opossum).
52. 3. Eutheria (Placental animals):
• They have a true Placenta (a well developed placenta is
formed).
• Uteri fuse to form a common vagina.
• Separate openings of Alimentary canal and
Urinogenital system.
It is divided into several orders:
Orders of Mammalia:
1. Insectivora: (mammals which eat insects)
E.g. Crocidura (Musk, shrew). Hemiechinus
(Hedge hog)
2. Edentata: (Toothless mammals) . They have protusable
tongue.
E.g. Dacipus (Armadillo) (reshape itselfinto
a ball and roll)
54. 3. Pholidata:
E.g. Manis (Pangolin) (can roll into a ball)
4. Rodentia: with gnawing inscissors.
E.g. Rattus (Rat), Mus musculus (Mouse),
Fanambulus (Squirrel)
5. Lagomorpha.
E.g. Oryctolagus (Rabbit),
Lepas (Hare)
62. 11. Carnivora: (Have well developed canines as they are
carnivorous mammals)
E.g. Panthera leo (Lion), Panthera tigris (Tiger), Panthera
pardus(Leopard), Canis lupus (wolf), Canis familiaris
(dog), Crocuta(Hyana), Felis domesticus (Cat), Ursus
(bear).
12.Primates: (most intelligent of all the mammals)
a. Prosimians: primitive primates (Tree dwelling)
E.g. Lemur, Loris, Tarsier.
b. Simians: includes monkeys and apes and man.
E.g. Macaca (Rhesus monkey), Cebus.
c. Apes:
E.g. Hylobates (Gibbon), Simia pongo (Orangutan),
Pan anthropitheus,(Chimpanzee), Gorilla,
Presbytes (langur),
d. Man: Homo sapiens (man).
67. Gorilla Simia pongo (Orangutan)
Pan anthropithecus
(Chimpazee)
Hylobates (Gibbon)
68. MONKEYS APES
1.Have tail Do not have tail
2. Small sized, with narrow chest Larger in size, with broader chest
3. They do not have Appendix They have Appendix
4. They are less intelligent They are moreintelligent
69. Primates:
The most advanced and developed Mammals.
1. Cerebrum most developed, most intelligent animals.
2. Have Binocular vision. ( The ability to focus both the eyes
to have correct depth and vision of the object).
3. Pollex (thumb) opposite to other fingers for good
grasping power in the hands.
4. Generally nails are present on the tips of the digits.
5. One or two young only are born.
6. Only two teats present on ventral thoracic wall.
7. Plantigrade locomotion ( on soles and palm).
70. BIBLIOGRA
PHY
Chapter: 4 ‘Chordata’ NCERT Class XIBiology
Text Book
Chapter: 4 ‘Chordata’ Modern’s abc of Biology
Class XI
Chapter: 4 ‘Chordata’ Pradeep’sText Book of
Biology Class XI
Chapter: 4 ‘Chordata’ Together with Biology,
Class XI, Rachna SagarPublications.
Chapter: 4 from printed noted prepared by
A. Jayashree, Biology Dept DPSHyderabad.
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