Complex Animals Chordata | Biology for Class 9 PDF Download

CHORDATA

                                                                                        (Gk. chorde-string)

Chordata is a phylum of triploblastic bilaterally symmetrical coelomate animals.

Diagnostic Characteristics :

(i) Notochord (Gk. noton-back, chorde-cord) : It is a long rod-like structure that develops between dorsal nervous system and gut. Notochord functions as a support structure that provides points for attachment to muscles.

(ii) Dorsal Hollow Nerve Cord : It occurs above the notochord.

(iii) Pharyngeal Gill Slits (Gill Pouches) : They are paired respiratory structures which remain functional throughout life in fishes and some amphibians. In others they occur only in embryo.

(iv) Post anal Tail. It occurs in most chordates for balancing, protection of genital and anal regions.

Protochordata [Lower chordates]

General Characters :

1. Exclusively all are marine.

2. These are bilaterally symmetrical, triploblastic and coelomic animals.

3. They have a rod-like structure i.e. notochord at some stages during their lives.

4. Pharyngeal gill clefts are found throughout the life span.

5. They have a dorsal tubular nerve cord.

6. Protochordes may be grouped into following subphyla-

(i) Hemichordata (ii) Urochordata (iii) Cephalochordata

Subphylum- Hemichordata

General Characters :

1. These animals possess a combination of nonchordate and chordate characters.

2. They are soft, unsegmented, worm like and bilateral symmetrical animals..

3. They have notochord as buccal diverticulum or stomochord in proboscis.

4. Body is divided into proboscis, collar and trunk.

e.g. Balanoglossus - Acorn worm.

Subphylum- Urochrodata

General Characters :

1. Notochord is present only in the tail of free living tadepole like larva

2. Adult members have test all over their body, made up of tunicin (just like cellulose).

e.g. Herdmania _ Sea potato or sea squirts.

Subphyum _ Cephalochordata

General Characters

1. First complete chordate animals.

2. Notochord, Nerve cord and pharyngeal gill clefts remain throughout the life span.

e.g. Branchiostoma or Amphioxus (Lancelet _ Typical chordate)

VERTEBRATA

General Characters :

1. Vertebrates are bilaterally symmetrical, triploblastic, coelomic and segmented animals.

2. In vertebrates notochord is replaced by vertebral column. 

3. Nerve cord remains enclosed within vertebral column.

Vertebrata are grouped into five classes

(i) Pisces (ii) Amphibia (iii) Reptilia (iv) Aves (v) Mammalia

                                                                                              Pisces

General Characters :

1. This class includes true fishes.

2. They are exclusively water living animals.

3. Their body is streamlined and covered by scales.

4. They have paired fins for locomotion.

5. They respire through gills.

6. Heart is two chambered.

7. Their endoskeleton is made up of cartilage or bones.

8. They are unisexual and lay eggs.

9. They are cold blooded.

Fishes are of two types based on the nature of their endoskeleton.

1. Cartilaginous fishes      2. Bony fishes

Amphibia

                                                                          [Gk. Amphi = two ; bios = life]

General Characters :

1. These are the first vertebrate which come out of water but these are not able to live on land permanently. These depend on water for their reproduction.

2. Their skin is smooth or rough, moist, slimy, glandular and without scales. To moist the skin numberous glands are found and skin having pigment cells (chromatophores) for colouration.

3. Notochord does not persist in adults.

4. Head and trunk distinct, tail may be present.

5. Two pairs of pentadactyl (five digits) limbs are present. Digits without claws.

6. Three chambered heart has two auricles and one ventricle.

7. Respiration by gills, lungs, skin and buccal lining.

8. Excrete either ammonia (by tadepole) or urea (by adults)

9. They are cold-blooded animals.

10. Animals are unisexual; fertilization external, mostly lay eggs.

e. g. Ichthyophis _ Blindworm

Salamander (Salamandra) Necturus _ Mud puppy

Siren _ Mudeel Bufo _ Common toad

Hyla _ Tree-frog Ranatigrina _ Indian bull frog

Alytes _ Midwife toad

Reptilia

                                                                                    [L. reptare = to creep]

General Characters :

1. First successful terrestrial animals but some are aquatic.

2. Body is divided into head, neck, trunk and tail.

3. Skin is dry, cornified, rough and nonglandular.

4. Two pairs of pentadactyl limbs with incurved nails or claws

5. Exoskeleton is made up of horny epidermal scales or dermal scute or bony plates.

6. Heart is three chambered i. e. two auricles and an incompletely divided ventricle. Only crocodiles have four chambered heart.

7. One pair of metanephric kidneys, animals are uricotelic

8. Fertilization is internal.

9. These are mostly oviparous, eggs are cleidoic i.e. eggs are covered by a shell made up of calcium carbonate
 

10. These are cold blooded animals.

Testudo _ Land tortoise                Trionyx _ Fresh water terrapins

Chelone _ marine turtles               Hemidactylus _ Common lizard, wall lizard

Calotes _ Garden lizard Girgit       Varanus _ Goh, monitor lizard.

Python _ Azgar, largest snake       Ptyas _ Zamenis or Rat snake or Dhaman

Eryx _ Sand boa _ Dumuhisnake  Typhlops _ Blind snake

Naja _ Indian Cobra                       Najabungarus _ King cobra

Crotalus _ Rattle snake                  Bangarus _ Krait snake

Vipera _ Viper snake                      Crocodilus _ Crocodile (Muggar)

Gavialius _ Gharial

                                                                                          Aves

                                                                                      [L. avis = bird]

General Characters :

1. All types of birds are included in this class.

2. Body is boat shaped and covered by soft feathers, called "plumage".

3. Fore limbs modified into wings for flight.

4. Hind-limbs bear four clawed digits and are adapted for walking and perching.

5. Teeth are absent, jaws form a horny beak.

6. Endoskeleton is made up of hollow, air-filled bones, known as pneumatic bone.

7. Four chambered heart with two auricles and two ventricles is present.

8. They excrete uric acid.

9. Sound producing organ at the junction of trachea and bronchi of birds is calledsyrinx.

10. Parental care is present.

11. Fertilization internal. They are oviparous and lay large, eggs having hard shell.

12. They are warm-blooded animals.

Penguins, Emu, Ostrich and Kiwi are flightless birds.

Archaeopteryx _ Connecting link between reptiles and birds.    Gallus _ Chicken

Passer _ House sparrow   Corvus _ Crow          Columba _ Pigeon

Psittacula _ Parrot            Pavo _ Peacock

                                                                                 Mammalia

                                                                            [L. mamma = Breast]

General Characters :

1. Members are cosmopolitan.

2. Body is divided into head, neck, trunk and tail with movable eyelids

3. Mammary glands are found in females for baby feeding.

4. The body is covered by a coat of hairs (made of keratin). Cutaneous glands such as sweat glands and oil glands.

5. They have two pairs of pentadactyl limbs.

6. Fleshy external ear (pinnae) present.

7. Respiration is by one pair of lungs.

8. A horizontal diaphragm present in between thorax and abdomen.

9. Heart is four chambered. Non-nucleated red blood corpuscles are present in blood.

10. They excrete urea i.e. ureotelic.

11. Mammals are warm-blooded animals.

12. Sexes are separate, internal fertilization present, mostly viviparous but a few are oviparous and lay eggs (e.g. Platypus & Echidna), and some like Kangaroos give birth to very poorly developed young ones.

e.g. Ornithorhyncus _ Duck billed platypus  Tachyglossues _ Echidna or spiny anteater

Macropus _ Kangaroo                                 Pteropus _ Flying fox or Bat

Funambulus _ Squirrel                               Ratusratus _ Rat

Balaenoptera - Blue whale                          Canis _ Dog

Felis _ Cat                                                Pantheraleopersica _ Lion

Pantheratigris _ Tiger                              Gorilla _ Largest ape

Organguttan _ Man of forest                      Homo sapiens _ Man

                                                                   Special points

• Hemichordata _ Connecting link between non-chordata and chordata.
• Archaeopteryx _ Connecting link between reptiles and aves.
• Ornithorhynchus&Tachyglossus - Connecting link between reptiles and mammals.
• Neopilina _ Connecting link between annelida and mollusca.
• Peripatus _ Connecting link between Annelida and Arthropoda.
• Phlebotomy _ To suck impure blood by leech.
• Leech have an anticlotting agent ' hirudin'.
• Mammology _ Study of mammals.
• Ornithology _ Study of birds.
• Dr. Salim Ali _ Birdman of India.
• Pterylosis _ Arrangement of wings on the body of birds.
• Nidology _ Study of birds nests.
• Ophiology or Serpantology _ Study of snakes.
• Herpetology _ The branch of biology which deals with the study of reptiles.
• Icthyology - Study of true fishes.
• Oology - Study of eggs of birds.
• The largest bird is ostrich.
• The fastest flying bird is swift, with flying speed is 171 kilometres per hour.
• Saurology - The branch of biology which deals with the study of lizards.
• Malacology - Study of molluscs.
• Conchology - Study of shells of molluscs.
• Mammals : Largest - Blue whale
• Longest - Giraffe
• Smallest - Shrew
• Longest Lived - Human being.
• T.H. Huxley said "bird are glorified reptiles".