ISC 11>CONTENT>2 DIVERSITY OF LIFE> 4.ANIMAL KINGDOM> CHORDATA

SCOPE OF SYLLABUS

Animal Kingdom: 
Chordata – sub phyla Hemichordata, Urochordata, Cephalochordata and Vertebrata (classes - pisces, amphibia, reptilia, aves and mammalia).

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ASCIDIAN 


CHORDATES- EBOOK

PHYLUM HEMICHORDATA

Features of Hemichordata:
  1. Hemichordata is a small, unusual phylum of worm-like creatures closely related to the phylas Chordata and Echinodermata.
  2. Body divisible into proboscis, collar and trunk.
  3. Notochord in the anterior end of the body in the form of buccal diverticulum - stomochord.
Eg: Balanoglossus.

PHYLUM CHORDATA

Features of chordata:
  1. Bilaterally symmetrical, triploblastic with organ system of body organization.
  2. Notochord present at some stage or replaced by a backbone or ring –like vertebral column.
  3. Alimentary canal placed ventral to the nerve cord.
  4. Respiration by gills or lungs.
  5. Nervous system hollow.
  6. Nerve cord single, dorsal, hollow without ganglia.
  7. Gill clefts present at some stage of life.
  8. Closed circulatory system with ventrally located heart.
The three basic features of chordates are
  • Presence of notochord.
  • Presence of dorsal tubular nerve cord.
  • Presence of pharyngeal gill slits at some stage of life.

NOTOCHORD 

Formation of notochord during embryogenesis.
Notochord is a dorsal flexible, firm rod like structure all along the length of the body. This provides support to the body. It may be present throughout or embryonic stage of life.
Chordates are broadly divided into two groups- Protochordates and Vertebrates.
Protochordates or Acraniata is a group of primitive animals that do not have a vertebral column. The notochord is seen either throughout or at some stage of their life. 
This includes two sub phylum- 1. Urochordata and 2. Cephalochordata.

Subphylum Urochordata or Tunicata 

Features of Urochordates or Tunicates
  1. They are bag-like, sessile, filter feeding animals.
  2. Commonly called ascidians.
  3. Body covered with tunic or test in adult stage.
  4. Notochord and nerve chord present in the tail in larval stages.
  5. These are lost during metamorphosis. This is called retrogressive metamorphosis.
  6. Numerous gill clefts  present in adults.
Eg. Herdmania, Doliolum

EXAMPLES OF UROCHORDATA

DOLIOLUM
HERDMANIA

Subphylum Cephalochordata 

Features of Cephalochordata:
  1. These are fish like, marine, filter feeding animals.
  2. Notochord present in the entire length of the body, and persists  throughout the life.
  3. Nerve cord hollow, but not differentiated into brain and spinal cord.
  4. Gill slits and fins present.
Ex. Amphioxus

Subphylum Vertebrata

Features of vertebrates:
  1. The notochord is replaced by a string of ring like bones called vertebrae. This forms the vertebral column.
  2. The body is divisible into head, neck, trunk and tail.
  3. They have two sets of paired appendages.
  4. Exoskeleton in the form of scales, feathers or hairs.
  5. Endoskeleton made up of cartilages or bones or both.
  6. Respiratory organs- gills or lungs.
  7. Nervous system differentiated into brain and spinal cord.

Group: Agnatha or Agnathostomata (without jaws)  

Features of Agnatha:
  • These are jaw-less vertebrates or mouth without jaws.
  • Notochord persists throughout life.
  • Paired appendages are absent.
  • Skin is soft and slimy without exoskeleton.

Class Cyclostomata (circular mouth) 

Features of cyclostomata:
  1. Body elongated rounded and eel like.
  2. Skin soft smooth and without exoskeleton.
  3. Paired fins or appendages absent.
  4. Skeleton cartilaginous.
  5. Notochord persistent.
  6. Heart two chambered.
Eg. Petromyzon (lampery), Myxine (Hag fish)

EXAMPLES OF CYCLOSTOMATA

PETROMYZON
MYXINE

Group: Gnathostomata ( which bears jaws) 

Features of Gnathostomata:
  • Mouth bounded by jaws.
  • Notochord replaced by vertebral column
  • Paired appendages present.
  • Skin covered with scales, feathers or hairs.

Gnathostomata has 2 super classes- Pisces and Tetrapod. 

Superclass: Pisces 

Includes fishes with fins as locomotory organs and gills for respiration.
Pisces has two main classes-  1. Chondrichthyes      2. Oesteichthyes 

Class  Chondrichthyes

Features of Chondrichthyes: 
  1. All marine fishes with cartilaginous endoskeleton.
  2. Body streamlined with five pairs of gill-slits without operculum.
  3. Skin covered with placoid scales.
  4. Do not have swim bladder.
  5. Tail is heterocercal.
  6. They are ovo-viviparous or viviparous
  7. Commonly sharks and rays.
Eg- Scoliodon, Torpedo

EXAMPLES OF CHONDRICHTHYES

SHARK
TORPEDO RAY

Class- Osteichthyes 

Features of osteichthyes:
  1. Found in all types of water.
  2. Spindle shaped or stream lined body.
  3. Paired lateral and median fins present gill slits covered with operculum.
  4. Endoskeleton bony.
  5. Skin with cycloid or ctenoid scales.
  6. Swim bladder present.
  7. Shows presence of lateral line.
  8. Jaws with teeth inside.
  9. Heart two chambered.
  10. 10 pairs of cranial nerves present.
Eg. Labeo, catla, sea-horse etc.

EXAMPLES OF OSTEICHTHYES

LABEO BICOLOUR
SEAHORSE

Find out the differences between cartilaginous and bony fishes

Super class Tetrapoda 

  • Two pairs of pentadactyl limbs for locomotion.
  • Endoskeleton bony, skin with scales, feathers or hairs.
  • Heart 3-4 chambered and shows double circulation.

Tetrapoda is divided into 4 classes-
  1. Amphibia
  2. Reptilia
  3. Aves
  4. Mammals 

Class- Amphibia 

Features of amphibia:
  1. Aquatic, semi aquatic terrestrial mode of life.
  2. Carnivorous and poikilothermal.
  3. Skin smooth or rough. Endoskeleton bony.
  4. Eye has nictitating membrane.
  5. Respiration by lungs or skin.
  6. Heart 3 chambered
  7. Development indirect with tadpole stage.
Eg. Salamander, Frog, Toad and Icthyophis. 

EXAMPLES OF AMPHIBIA

SALAMANDER
ICHTHYOPIS

Find out the differences between Frog and Toad

FROG
TOAD

Class- Reptilia 

Features of Reptilia:
  1. First true land vertebrates, usually terrestrial.
  2. Poikilotherms, body covered with scales.
  3. Respiration by lungs.
  4. Heart incompletely four chambered, except crocodiles.
  5. Excretion uricotelic.
  6. Brain well developed with 12 pairs of cranial nerves.
  7. Oviparous animals.
  8. All the extinct form like dinosaurs are included in this class.
Eg. Tortoise, Crocodile, Alligators etc.

EXAMPLES OF REPTILIA

CROCODILE
SNAKE

Find out the differences between turtle and tortoise

Reptiles are true land vertebrates

Picture
Reptiles are considered to be true land vertebrates. Even though some reptiles like turtles are aquatic they come on land to lay eggs.
The eggs have extra-embryonic membranes that protect and nourish the embryos. 

Class- Aves 

Features of Aves:
  1. Presence of feathers and power of flight.
  2. Homeotherm, exoskeleton made up of feathers.
  3. Fore limbs modified to form wings.
  4. Respiration by lungs.
  5. Heart is four chambered.
  6. Excretion uricotelic.
  7. Brain well developed, 12 pairs cranial nerves.
  8. Oviparous.
Eg. Flamingo, Kite, Pigeon etc.

EXAMPLES OF AVES

FLIGHTLESS BIRDS

Class- Mammalia 

Features of mammalia:
  1. Warm blooded, homeothermals.
  2. Skin more or less covered with hairs.
  3. Mammary glands present in females.
  4. External ear pinnae present.
  5. Heart four chambered, lungs well developed.
  6. Viviparous.

Two subclasses: Prototheria and Theria.
Prototheria are egg laying mammals. Eg. Echindna.
Theria give birth to their young ones.
Two infra classes Metatheria (marsupial) and Eutheria (placentalia)

EXAMPLES OF MAMMALIA

KANGAROO
DUCK BILLED PLATYPUS
NON-CHORDATES