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MHT-CET : Biology Entrance Exam

MHT - CET : Biology - Classification of Chordata Page 1

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1.

Introduction

 

  • The animal kingdom is divided into two sub-kingdoms or phyla:
    1. Chordata
    2. Non-chordata
  • The animals belonging to phylum chordata exhibit the following distinguishing characters at some stage in their life history:
    1. A skeletal rod called notochord which lies below the nerve cord and above the alimentary canal.
    2. A dorsal tubular nerve cord which lies above the notochord.
    3. Gill-clefts, which are, paired openings that lead from the pharynx to the exterior.
  • Phylum chordata is further divided into two sub-phyla:
    1. Protochordata
    2. Vertebrata

 

2.

General Characters of Sub-phylum Vertebrata

 

  • The animals belonging to sub-phylum vertebrata are distinguished by the following characters:
    1. They are triploblastic and possess bilateral symmetry.
    2. They posses a vertebral column which is mid-dorsal in position.
    3. A dorsal, tubular nerve cord is also present.
    4. Gill-clefts are present at least in embryonic stages.
    5. The skin is differentiated into an outer epidermis and a lower dermis.
    6. A post-anal tail is present.
    7. Heart is ventral in position.
    8. The blood contains red blood corpuscles.
    9. Example: Fish, frog, calotes, birds, rat, bat, man, etc.

 

3.

Classification of Vertebrates

 

  • Vertebrates are divided into five classes:
    1. Pisces
    2. Amphibia
    3. Reptilia
    4. Aves
    5. Mammalia

 

4.

General Characters of Class Pisces

 

  1. This includes all fishes which are aquatic animals.
  2. They are cold-blooded.
  3. Their body is streamlined.
  4. Their exoskeleton is in the form of scales.
  5. Endoskeleton may be cartilagenous or bony.
  6. Respiration is by gills.
  7. There is a presence of lateral line on either side of the body.
  8. Heart is two chambered, bears an auricle and a ventricle.
  9. Example: Scoliodon, labeo, etc.
    • The class Pisces is subdivided into two sub-classes.
      1. Chondrichtyes which includes cartilaginous fishes.
      2. Osteichthyes which includes bony fishes.

Scoliodon
Phylum - Chordata
Subphylum - Vertebrata
Class - Pisces
Sub-class - Chondrichthyes

General Characters:

  1. Body is spindle-shaped and laterally compressed. Colour is grey above and white beneath.
  2. It is commonly known as dog fish.
  3. Exoskeleton is in the form of placoid scales.
  4. It possesses fine pairs of gillslits without operculum.
  5. The head bears a pair of eyes, a long snout and a mouth which is ventral in position.
  6. The tail is provided with an asymmetrical caudal fin.
  7. The male bears claspers which act as external copulatory organs.

Labeo
Phylum - Chordata
Subphylum - Vertebrata
Class - Pisces
Sub-class - Osteichthyes

General Characters:

  1. The body is spindle-shaped, it has bluish black dorsal side and silvery white ventral and lateral sides.
  2. It is commonly known as Rohu.
  3. The body is covered by overlapping cycloid scales.
  4. The gills are covered by operculum.
  5. The head is large, bears a terminal mouth, and a pair of large eyes without eyelids.
  6. The caudal fin is symmetrical and deeply forked.

 

5.

General Characters of Class Amphibia

 

  1. The animals belonging to class Amphibia are cold-blooded.
  2. The larval stages are aquatic but the adults can live on land as well as in water.
  3. The skin is generally moist, smooth and without exoskeleton.
  4. Two pairs of pentadactyle limbs are present which are without claws.
  5. Larval forms respire through gills and adults respire through skin and lungs.
  6. Heart is three-chambered consisting of two auricles and one ventricle.
  7. Development is indirect and larva is formed which undergoes metamorphosis.
  8. Example: Frog, toad, salamander.

Toad
Phylum - Chordata
Subphylum - Vertebrata
Class - Amphibia

General Characters:

  1. Body is tailless.
  2. The skin is dry, rough, warty and without exoskeleton.
  3. The head bears a snout and a wide mouth without teeth.
  4. The eyes are large with movable eyelids.
  5. A circular tympanum lies behind each eye.
  6. A parotid gland is present behind each tympanum.
  7. The hindlimbs are longer than the forelimbs.

 

6.

General Characters of Class Reptilia

 

  1. They are cold-blooded, mostly terrestrial but a few like crocodiles are secondarily aquatic.
  2. The skin is dry and covered with horny scales, bony plates or scutes.
  3. Locomotion is by creeping.
  4. Respiration is by sac-like lungs.
  5. Heart is incompletely four-chambered with two auricles and an incompletely divided ventricle.
  6. Example: Calotes, snakes, turtles.

Calotes
Phylum - Chordata
Subphylum - Vertebrata
Class - Reptilia

  1. Calotes is commonly known as garden lizard.
  2. It has an elongated body which is covered with dry scales.
  3. A sharp crest of spines is present on the dorsal side of the neck.
  4. The head is triangular in shape consisting of a mouth, a pair of nostrils, a pair of ear openings in pits, and a pair of eyes with movable eyelids.
  5. Limbs are provided with five-clawed digits.

 

7.

General Characters of Class Aves

 

  1. They include all birds.
  2. They are warm-blooded animals.
  3. The body is streamlined and exoskeleton is in the form of feathers.
  4. The forelimbs are modified into wings which are used for flying.
  5. Legs are digited and clawed.
  6. Jaws are without teeth and are modified to form a beak.
  7. Heart is four-chambered.
  8. Lungs are connected to air sacs.
  9. A specialised sound box called syrinx is present at the base of the trachea.
  10. Example: Pigeon, parrot, duck, etc.

Parrot
Phylum - Chordata
Subphylum - Vertebrata
Class - Aves

General Characters:

  1. It is an arboreal bird.
  2. It is also kept as a pet bird, as it has the capability to mimic a few words.
  3. Generally the body is covered with green feathers.
  4. The head bears a pair of nostrils, a pair of eyes and a sharp and hooked beak which is red in colour.
  5. The male possesses a red-coloured ring around its neck called as collar.
  6. The collar is absent in females.

 

8.

General Characters of Class Mammalia

 

  1. This class includes highly developed and intelligent vertebrates, mostly terrestrial, although a few are aquatic (example: whale) and a few can fly in the air (example: bat).
  2. They are warm-blooded.
  3. Body is covered by hair or fur.
  4. Sweat glands, sebaceous glands and mammary glands (in females) are present.
  5. A diaphragm is present which divides the body into thorax and abdomen.
  6. Teeth are situated in bony sockets.
  7. External ear (Pinnae) are also present.
  8. Heart is four-chambered.
  9. Respiration is by lungs.
  10. Sexes are separate. They are mostly viviparous.
  11. Example: Bat, squirrel, rat, man.

Bat
Phylum - Chordata
Sub-phylum - Vertebrata
Class - Mammalia

General Characters:

  1. Bat is a flying mammal. It is nocturnal in nature.
  2. The body is covered by hair.
  3. The head bears a pair of small eyes and a pair of large pinnae which help in ecolocation.
  4. It has a fold of skin called patagium, lying between the forelimb and the hind limb on each side of the body. It is used for flying.

 

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