CBSE Class 11 Biology Animal Kingdom Notes Set 03

1. Phylum – Chordata
- Fundamentally characterised by the presence of à
- a notochord,
- a dorsal hollow nerve cord and
- paired pharyngeal gill slits
- Bilaterally symmetrical,
- Triploblastic,
- Coelomate
- Organ-system level of organisation.
- Possess a post anal tail
- Closed circulatory system.

2. Phylum Chordata is divided into three subphyla:
- Urochordata or Tunicata,
- Cephalochordata
- Vertebrata.

3. Subphyla Urochordata + Cephalochordata à Protochordates
- Exclusively marine.

4. In Urochordata à Notochord is present only in larval tail
- Examples: Urochordata – Ascidia, Salpa, Doliolum;

5. In Cephalochordata à Notochord extends from head to tail region and is persistent throughout their life.
- Examples: Cephalochordata – Branchiostoma (Amphioxus or Lancelet).

6. The members of subphylum Vertebrata
- Possess notochord during the embryonic period.
- The notochord is replaced by a cartilaginous or bony vertebral column in the adult.
- “all vertebrates are chordates but all chordates are not vertebrates”
- Besides the basic chordate characters,
- vertebrates have a ventral muscular heart with two, three or four chambers,
- kidneys for excretion and osmoregulation and
- paired appendages which may be fins or limbs.

7. Class – Cyclostomata
- All are ectoparasites on some fishes.
- Elongated body bearing 6-15 pairs of gill slits for respiration.
- Cyclostomes have a sucking and circular mouth without jaws
- Their body is devoid of scales and paired fins.
- Cranium and vertebral column are cartilaginous.
- Circulation is of closed type.
- Cyclostomes are marine but migrate for spawning to fresh water.
- After spawning, within a few days, they die.
- Their larvae, after metamorphosis, return to the ocean.
- Examples: Petromyzon (Lamprey) and Myxine (Hagfish).

8. Class – Chondrichthyes
- Marine animals
- Streamlined body
- Cartilaginous endoskeleton
- Mouth is located ventrally.
- Notochord is persistent throughout life.
- Gill slits are separate and without operculum (gill cover).
- The skin is tough, containing minute placoid scales.
- Teeth are modified placoid scales which are backwardly directed.
- Their jaws are very powerful.
- These animals are predaceous.
- Due to the absence of air bladder, they have to swim constantly to avoid sinking.
- Heart is two-chambered (one auricle and one ventricle).
- Some of them have electric organs (e.g., Torpedo) and some possess poison sting (e.g., Trygon).
- They are cold-blooded (poikilothermous) animals, i.e., they lack the capacity to regulate their body temperature.
- Sexes are separate.
- In males pelvic fins bear claspers.
- They have internal fertilisation and many of them are viviparous.
- Examples:
- Scoliodon (Dog fish),
- Pristis (Saw fish),
- Carcharodon (Great white shark),
- Trygon (Sting ray).

9. Class – Osteichthyes
- both marine and fresh water fishes
- Bony endoskeleton.
- Streamlined Body.
- Mostly terminal mouth
- Four pairs of gills ; covered by an operculum on each side.
- Skin is covered with cycloid/ctenoid scales.
- Air bladder is present which regulates buoyancy.
- Heart is two chambered (one auricle and one ventricle).
- They are cold-blooded animals.
- Sexes are separate.
- Fertilisation is usually external.
- They are mostly oviparous and development is direct.
- Examples:
- Marine – Exocoetus (Flying fish), Hippocampus (Sea horse);
- Freshwater – Labeo (Rohu), Catla (Katla), Clarias (Magur);
- Aquarium – Betta (Fighting fish), Pterophyllum (Angel fish).

10. Class – Amphibia (Gr., Amphi : dual, bios, life)
- Live in aquatic as well as terrestrial habitats
- Most of them have two pairs of limbs.
- Body is divisible into head and trunk.
- Tail may be present in some.
- The amphibian skin is moist (without scales).
- The eyes have eyelids.
- A tympanum represents the ear.
- Alimentary canal, urinary and reproductive tracts open into a common chamber called cloaca which opens to the exterior.
- Respiration is by gills, lungs and through skin.
- The heart is three chambered (two auricles and one ventricle).
- These are cold-blooded animals.
- Sexes are separate.
- Fertilisation is external.
- They are oviparous and development is indirect.
- Examples:
- Bufo (Toad),
- Rana (Frog),
- Hyla (Tree frog),
- Salamandra (Salamander),
- Ichthyophis (Limbless amphibia)

11. Class – Reptilia
- Creeping or crawling mode of locomotion (Latin, reptum, to creep or crawl).
- Mostly terrestrial animals
- Body is covered by dry and cornified skin, epidermal scales or scutes
- Do not have external ear openings.
- Tympanum represents ear.
- Limbs, when present, are two pairs.
- Heart is usually three-chambered, but four-chambered in crocodiles.
- Reptiles are poikilotherms.
- Snakes and lizards shed their scales as skin cast.
- Sexes are separate.
- Fertilisation is internal.
- They are oviparous and development is direct.
- Examples:
- Chelone (Turtle),
- Testudo (Tortoise),
- Chameleon (Tree lizard),
- Calotes (Garden lizard),
- Crocodilus (Crocodile),
- Alligator (Alligator).
- Hemidactylus (Wall lizard),
- Poisonous snakes –
o Naja (Cobra), Bangarus (Krait), Vipera (Viper).

12. Class – Aves
- The characteristic features à Presence of feathers
- Most of them can fly except flightless birds (e.g., Ostrich).
- They possess beak
- The forelimbs are modified into wings. 
- The hind limbs generally have scales and are modified for walking, swimming or clasping the tree branches.
- Skin is dry without glands except the oil gland at the base of the tail.
- Endoskeleton is fully ossified (bony)
- Long bones are hollow with air cavities (pneumatic).
- The digestive tract of birds has additional chambers, the crop and gizzard.
- Heart is completely four chambered.
- They are warm-blooded (homoiothermous) animals, i.e., they are able to maintain a constant body temperature.
- Respiration is by lungs.
- Air sacs connected to lungs supplement respiration.
- Sexes are separate.
- Fertilisation is internal.
- They are oviparous and development is direct.
- Examples :
- Corvus (Crow),
- Columba (Pigeon),
- Psittacula (Parrot),
- Struthio (Ostrich),
- Pavo (Peacock),
- Aptenodytes (Penguin),
- Neophron (Vulture).

13. Class – Mammalia
- Found in a variety of habitats – polar ice caps, deserts, mountains, forests, grasslands and dark caves.
- Adapted to fly or live in water.
- The most unique mammalian characteristic is the presence of milk producing glands (mammary glands) by which the young ones are nourished.
- They have two pairs of limbs, adapted for walking, running, climbing, burrowing, swimming or flying
- The skin of mammals is unique in possessing hair.
- External ears or pinnae are present.
- Different types of teeth are present in the jaw.
- Heart is four chambered.
- They are homoiothermous.
- Respiration is by lungs.
- Sexes are separate
- Fertilisation is internal.
- They are viviparous with few exceptions
- Development is direct.
- Examples:

Oviparouso
Ornithorhynchus (Platypus);

Viviparous –
o Macropus (Kangaroo),
o Pteropus (Flying fox),
o Camelus (Camel),
o Macaca (Monkey),
o Rattus (Rat),
o Canis (Dog),
o Felis (Cat),
o Elephas (Elephant),
o Equus (Horse),
o Delphinus (Common dolphin),
o Balaenoptera (Blue whale),
o Panthera tigris (Tiger),
o Panthera leo (Lion).