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- A rod like structure called notochord lying above the digestive tract.
- A tubular nerve cord lying above the notochord.
- A pair of gill slits in the pharangeal region.
- Sub phylum urochordata.
- Sub phylum cephalochordata.
Sub phylum Urochordata
- Marine in habitat.
- Notochord is found in the tail in the larval form. Hollow nerve cord is also present in the larva.
- Body is covered by a tunic.
- Phyarynx has several gill slits.
Example:
Herdmania, Doliolum, Pyrosoma
Sub phylum cephalochordata
- Headless, tiny fish-like chordates.
- Notochord, nerve cord without a distinct brain, gill slits and a port anal tail present.
Example:
Branchiostoma (Amphioxus)
Subphylum vertebrata
- This includes the majority of chordates.
- Head is prominent.
- Nervous system and exoskeleton are highly developed.
- Notochord is replaced by a jointed vertebral column.
- Two pairs of appendages (limbs).
- Aquatic animals have gills.
Subphylum vertebrata is sub divided into seven classes
- Cyclostomata
- Chondrichthyes
- Osteichthyes
- Amphibia
- Reptilia
- Aves
- Mammalia
Class cyclostomata
- Very primitive vertebrates.
- Do not have jaws. Being ectoparasites, mouth is of the sucking type with the help of which they stick to the host.
- Notochord present.
- Respiration is by gills enclosed in pouches.
- Heart has two chambers.
- Is cold blooded.
- Gonad is single and fertilization is external.
Example:
Petromyzon (Lamprey)
Class chondrichthyes (cartilaginous fish)
- Large marine organisms.
- Body is flat, disc shaped or spindle shaped.
- Body is covered with placoid scales.
- Skeleton is cartilaginous.
- Respiration is through gills.
- Heart is two chambered.
Example:
Scoliodon (Indian shark), Torpedo (electric ray), Trygon (sting ray)
Class Osteichthyes (bony fish)
- Found in lakes, rivers and seas.
- Spindle shaped body covered with cycloid or tenoid scales.
- Mouth is anterior.
- Skeleton is partly or completely bony.
- Gills are filamentous.
- Heart is two chambered.
Example:
Labeo (carp), Exocoetus (flying fish), Hippocampus (sea horse),
Anabas (climbing perch), Protopterus (lung fish)Class amphibia
- Live in both water and on land.
- Respiration is by gills, lungs or skin.
- 3 chambered heart.
- Is cold blooded.
- Have two pairs of pentadactyl (5 digit) limbs which may be absent in some cases.
Example:
Rana (frog), Bufo (toad), Hyla (tree frog), Necturus
Class Reptilia (creeping vertebrates)
- Mostly terrestrial.
- Heart is 3 chambered, is cold blooded.
- Breathe through lungs.
- Body covered with scales.
- Have two pairs of pentadactyl (five digit) limbs which are absent in snakes.
Example:
Hemidactylus (wall lizard), chameleon, Draco (flying lizard)
Class Aves (birds)
- Arboreal in habitat i.e, they live on trees.
- Warm blooded. 4 chambered heart.
- Body covered with feathers.
- Lungs have membranous extensions called air sacs to make the body light.
- Mouth is surrounded by a beak. Teeth are absent.
- Fore-limbs are modified into wings.
Class mammalia (mammals)
- Most intelligent of all organisms.
- Warm blooded with 4 chambered heart.
- Give birth to young ones.
- The mother suckles her young ones on milk secreted by special glands called mammary glands.
- Body covered with hair.
- Have two pairs of pentadactyl limbs.
- Breathe through lungs.










