ANIMAL KINGDOM
Capsule Notes for NEET & CBSE Class 11 Biology
📥 Download Complete NotesBasis of Classification
1. Levels of Organisation
- Cellular level: Cells arranged as loose aggregates (e.g., Sponges)
- Tissue level: Cells performing same function arranged into tissues (e.g., Coelenterates)
- Organ level: Exhibited by Platyhelminthes and higher phyla
- Organ system level: Organs associate to form functional systems (e.g., Annelids, Arthropods, Molluscs, Echinoderms, Chordates)
2. Symmetry
- Radial symmetry: Any plane through central axis divides organism into identical halves (e.g., Coelenterates, Ctenophores, Echinoderms)
- Bilateral symmetry: Body divisible into identical left and right halves in only one plane (e.g., Annelids, Arthropods)
3. Germ Layers
- Diploblastic: Two embryonic layers (ectoderm and endoderm) with mesoglea in between (e.g., Coelenterates)
- Triploblastic: Three layers including mesoderm (Platyhelminthes to Chordates)
4. Body Cavity (Coelom)
- Acoelomates: Body cavity absent (e.g., Platyhelminthes)
- Pseudocoelomates: Body cavity not lined by mesoderm (e.g., Aschelminthes)
- Coelomates: Body cavity lined by mesoderm (e.g., Annelids, Molluscs, Arthropods, Echinoderms, Chordates)
5. Other Features
- Digestive system: Complete (mouth and anus) vs Incomplete (single opening)
- Metamerism: Body divided into segments with serial repetition of organs (e.g., Earthworm)
Phyla of Non-Chordates
Phylum Porifera (Sponges)
Characteristics: Cellular level of organisation, water transport system with ostia and osculum, choanocytes line spongocoel, skeleton of spicules/spongin, hermaphrodites.
Examples: Sycon, Spongilla (Fresh water sponge), Euspongia (Bath sponge)
Phylum Coelenterata (Cnidaria)
Characteristics: Tissue level organisation, cnidoblasts with nematocysts, gastro-vascular cavity, polyp and medusa forms, alternation of generations.
Examples: Physalia (Portuguese man-of-war), Adamsia (Sea anemone), Pennatula (Sea-pen), Gorgonia (Sea-fan), Meandrina (Brain coral), Hydra, Obelia, Aurelia
Phylum Ctenophora
Characteristics: Eight rows of ciliated comb plates, bioluminescence, sexual reproduction only.
Examples: Pleurobrachia, Ctenoplana
Phylum Platyhelminthes (Flatworms)
Characteristics: Dorso-ventrally flattened, acoelomate, hooks and suckers in parasitic forms, flame cells for excretion, high regeneration capacity.
Examples: Taenia (Tapeworm), Fasciola (Liver fluke), Planaria
Phylum Aschelminthes (Roundworms)
Characteristics: Circular cross-section, pseudocoelomate, complete alimentary canal, dioecious.
Examples: Ascaris (Roundworm), Wuchereria (Filaria worm), Ancylostoma (Hookworm)
Phylum Annelida
Characteristics: Metameric segmentation, longitudinal and circular muscles, parapodia in aquatic forms, nephridia for excretion.
Examples: Nereis (Aquatic), Pheretima (Earthworm), Hirudinaria (Leech)
Phylum Arthropoda
Characteristics: Largest phylum, chitinous exoskeleton, jointed appendages, various respiratory organs, malpighian tubules for excretion.
Examples: Apis (Honey bee), Bombyx (Silkworm), Laccifer (Lac insect), Anopheles/Culex/Aedes (Vectors), Locusta (Locust), Limulus (Living fossil)
Phylum Mollusca
Characteristics: Second largest phylum, calcareous shell, unsegmented body with head, muscular foot, visceral hump, mantle cavity with gills, radula for feeding.
Examples: Pila (Apple snail), Pinctada (Pearl oyster), Sepia (Cuttlefish), Loligo (Squid), Octopus, Aplysia (Sea-hare), Dentalium (Tusk shell), Chaetopleura (Chiton)
Phylum Echinodermata
Characteristics: Calcareous endoskeleton, radial symmetry in adults (bilateral in larvae), water vascular system, no excretory system.
Examples: Asterias (Star fish), Echinus (Sea urchin), Antedon (Sea lily), Cucumaria (Sea cucumber), Ophiura (Brittle star)
Phylum Hemichordata
Characteristics: Stomochord in collar region, cylindrical body with proboscis, collar and trunk, proboscis gland for excretion.
Examples: Balanoglossus, Saccoglossus
Phylum Chordata
Subphyla of Chordata
- Urochordata: Notochord only in larval tail (e.g., Ascidia, Salpa, Doliolum)
- Cephalochordata: Notochord extends head to tail, persistent throughout life (e.g., Branchiostoma)
- Vertebrata: Notochord replaced by vertebral column in adults
Classes of Vertebrata
Class Cyclostomata (Jawless Fishes)
Ectoparasites, elongated body, 6-15 pairs of gill slits, circular sucking mouth, no scales or paired fins, marine but migrate to fresh water for spawning.
Examples: Petromyzon (Lamprey), Myxine (Hagfish)
Class Chondrichthyes (Cartilaginous Fishes)
Cartilaginous endoskeleton, ventral mouth, placoid scales, no air bladder, electric organs/poison stings in some, pelvic claspers in males.
Examples: Scoliodon (Dog fish), Pristis (Saw fish), Carcharodon (Great white shark), Trygon (Sting ray), Torpedo (Electric organ)
Class Osteichthyes (Bony Fishes)
Bony endoskeleton, terminal mouth, 4 pairs of gills with operculum, cycloid/ctenoid scales, air bladder present.
Examples: Marine - Exocoetus (Flying fish), Hippocampus (Sea horse); Freshwater - Labeo (Rohu), Catla, Clarias (Magur); Aquarium - Betta (Fighting fish), Pterophyllum (Angel fish)
Class Amphibia
Aquatic and terrestrial habitats, moist skin without scales, tympanum for hearing, cloaca, three-chambered heart.
Examples: Bufo (Toad), Rana (Frog), Hyla (Tree frog), Salamandra (Salamander), Ichthyophis (Limbless amphibia)
Class Reptilia
Creeping/crawling locomotion, dry cornified skin with scales/scutes, no external ear openings, three-chambered heart (four in crocodiles).
Examples: Chelone (Turtle), Testudo (Tortoise), Chameleon, Crocodilus (Crocodile), Naja (Cobra), Bangarus (Krait), Vipera (Viper)
Class Aves (Birds)
Feathers, beak, forelimbs modified into wings, scales on hind limbs, pneumatic bones, crop and gizzard, warm-blooded, four-chambered heart, air sacs.
Examples: Corvus (Crow), Columba (Pigeon), Psittacula (Parrot), Struthio (Ostrich), Pavo (Peacock), Aptenodytes (Penguin), Neophron (Vulture)
Class Mammalia
Mammary glands, hair on skin, external pinnae, heterodont dentition, mostly viviparous.
Examples: Oviparous - Ornithorhynchus (Platypus); Viviparous - Macropus (Kangaroo), Pteropus (Flying fox), Camelus (Camel), Macaca (Monkey), Rattus (Rat), Canis (Dog), Felis (Cat), Elephas (Elephant), Equus (Horse), Delphinus (Dolphin), Balaenoptera (Blue whale), Panthera tigris (Tiger), Panthera leo (Lion)