Animal Kingdom | Plus 1 Exam Capsule Notes (Web and PDF)



1. Levels of organization
  • Cellular level: Loose cell aggregates. E.g. Porifera.
  • Tissue level: Cells to tissues. E.g. Cnidaria & Ctenophora.
  • Organ level: Tissues to organs. E.g. Platyhelminthes to chordates.
  • Organ system level: Organs to organ systems. E.g. higher animals.
2. Body symmetry

    Arrangement of similar parts on either side of body.
  • Asymmetrical: No symmetry. E.g. Most Poriferans, Snails.
  • Radial symmetry: Body can be cut into 2 equal halves in any plane along central axis. E.g. some Poriferans, Cnidarians, Ctenophores & adult Echinoderms.
  • Bilateral symmetry: Body can be cut into right & left halves in only one plane. E.g. Flatworms to Chordata (except adult Echinodermata).
Radial Symmetry

Bilateral Symmetry

3. Embryonic layers
  • Diploblastic: Ectoderm & endoderm. E.g. Cnidaria & Ctenophora.
  • Triploblastic: Ectoderm, mesoderm & endoderm. E.g. Flatworms to Chordata.

4. Coelom

    Cavity b/w body wall & gut wall.
  • Acoelomate: No coelom. E.g. Porifera to Platyhelminthes.
  • Pseudocoelomate: False coelom. E.g. Aschelminthes.
  • Coelomate: True coelom. E.g. Annelida to Chordata.

5. Metamerism
  • Segmentation. 
  • E.g. Annelids (earthworm etc.), Arthropods.
6. Notochord
  • Mesodermally derived rod on the dorsal side of embryo. 
  • Only in Chordata.


1. Porifera (Sponges)
  • Water canal system (water → ostia → spongocoel → osculum).
  • Spongocoel & canals are lined with choanocytes (collar cells).
  • Body is supported by spicules and spongin fibres.
  • Examples: Sycon (Scypha), Spongilla (fresh water sponge), Euspongia (Bath sponge).
2. Cnidaria (Coelenterata)
  • Tentacles with cnidoblasts (stinging cells).
  • Gastro-vascular cavity (coelenteron) with mouth on hypostome. 
  • Polyp & Medusa forms. 
  • Some shows alternation of generation (metagenesis).
  • Examples: Hydra, Obelia, Aurelia, Physalia (Portuguese man of war), Adamsia (Sea-anemone).
3. Ctenophora (Comb jellies)
  • Locomotion is by ciliated comb plates.
  • Shows Bioluminescence (ability to emit light).
  • Examples: Ctenoplana, Pleurobrachia.
4. Platyhelminthes (Flatworms)
  • Unsegmented, dorso-ventrally flattened body.
  • Excretion by Flame cells.
  • Parasites have Hooks & suckers.
  • Examples: Taenia solium (Tape worm), Fasciola (Liver fluke), Planaria.
5. Aschelminthes (Roundworms)
  • Pseudocoelomate. 
  • Body is circular in cross section.
  • An excretory tube to remove waste through excretory pore.
  • Females are longer than males.
  • Examples: Ascaris (Roundworm), Ancylostoma (Hookworm), Wuchereria (Filarial worm).
6. Annelida (Segmented or Ringed worms)
  • Segmentation like rings.
  • Longitudinal & circular muscles help in locomotion.
  • Closed type circulatory system.
  • Locomotory organs: Setae (in earthworm) or parapodia (in Neries).
  • Excretion by Nephridia.
  • Examples: Pheretima (earthworm), Hirudinaria (Leech), Neries. 
7. Arthropoda (Joint-legged animals)
  • Jointed appendages.
  • Body has head, thorax & abdomen.
  • Chitinous cuticle (exoskeleton).
  • Excretion by Malpighian tubules.
  • Sensory organs are antennae, compound & simple eyes, statocysts (balance organs).
  • Economically important insects: Apis, Bombyx, Laccifer.
  • Vectors: Mosquitoes, Housefly.
  • Gregarious pest: Locusta.
  • Living fossil: Limulus (King crab)
8. Mollusca (Soft-bodied animals)
  • Body has head, visceral hump & muscular foot.
  • Head has sensory tentacles. 
  • Calcareous shell.
  • Feather-like gills for respiration & excretion.
  • Mantle & radula (rasping organ).
  • Examples: Pila (Apple Snail), Pinctada (Pearl Oyster), Sepia (Cuttlefish), Loligo (Squid), Octopus (Devil fish).
9. Echinodermata (Spiny-skinned animals)
  • Adults radial. Larvae bilateral.
  • Endoskeleton of calcareous ossicles (Spiny bodied).
  • Water vascular system for locomotion, food capture and respiration. Excretory system absent. 
  • Examples: Asterias (Starfish), Echinus (Sea Urchin), Echinocardium, Antedon (Sea Lily), Cucumaria (Sea Cucumber), Ophiura (Brittle Star).
10. Hemichordata
  • Body is formed of proboscis, collar & trunk.
  • Collar bears stomochord. 
  • Excretion by Proboscis gland.
  • Examples: Balanoglossus (Tongue worm), Saccoglossus.


Differences between Chordata & Non-Chordata 



1.  Notochord


2.  Central nervous system is dorsal.


3.  Pharyngeal gill slits


4.  A post-anal part (tail)


5.  Ventral heart

Dorsal heart

Phylum Chordata is classified into 3 subphyla: Urochordata, Cephalochordata & Vertebrata.

  • Notochord present only in larval tail.
  • E.g. Ascidia, Salpa, Doliolum.
  • Notochord from head to tail region and is persistent throughout life.
  • E.g. Branchiostoma (Amphioxus or Lancelet).
  • Notochord during embryonic period.
  • It is replaced by cartilaginous or bony vertebral column in the adult.
  • Paired appendages (fins or limbs).


  • All are ectoparasites on some fishes.
  • Elongated body without scales and paired fins.
  • Sucking and circular mouth without jaws.
  • Cartilaginous cranium and vertebral column.
  • Marine, but migrate for spawning to fresh water.
  • E.g. Petromyzon (Lamprey) and Myxine (Hagfish).


Class Chondricthyes (Cartilaginous fishes)
  • Cartilaginous endoskeleton.
  • Ventral mouth.
  • Gill slits without operculum.
  • Skin with placoid scales.
  • No air bladder. So, needs to swim to avoid sinking.
  • In males, pelvic fins bear claspers.
  • Internal fertilization. Many are viviparous.
  • Examples: Scoliodon (Dogfish), Pristis (Saw fish), Carcharodon (Great white shark), Trygon (Sting ray), Torpedo (Electric ray). 
Class Osteichthyes (Bony fishes)
  • Bony endoskeleton.
  • Terminal mouth.
  • 4 pairs of gills covered by operculum on each side.
  • Scales are Cycloid, ctenoid etc.
  • Air bladder for buoyancy.
  • External fertilisation. Mostly oviparous. 
  • Marine: Exocoetus (flying fish), Hippocampus (seahorse) 
  • Fresh water: Labeo (Rohu), Catla (Katla), Clarias (Magur).
  • Aquarium: Betta (Fighting fish), Pterophyllum (Angel fish).


Class Amphibia
  • Live in aquatic & terrestrial habitats. 
  • Need water for breeding. 
  • Moist skin without scales. 
  • Cloaca.
  • Examples: Bufo, Rana, Hyla, Salamandra, Ichthyophis (Limbless amphibia).
Class Reptilia
  • Dry & cornified skin.
  • Epidermal scales or scutes.
  • Crawling locomotion.
  • Examples: Chelone, Testudo, Chameleon, Calotes, Crocodilus, Alligator, Hemidactylus, Naja, Bangarus, Vipera.
Class Aves (Birds)
  • Feathers, beak & wings.
  • Dry skin without glands except oil gland at tail base.
  • Hind limbs have scales.
  • Pneumatic bones. 
  • Digestive tract has crop & gizzard.
  • Examples: Corvus, Columba, Psittacula, Struthio.
Class Mammalia
  • Mammary glands. 
  • Skin with hair. 
  • Teeth different types. 
  • Viviparous.
  • Examples: Ornithorhynchus, Macropus, Pteropus, Camelus, Macaca, Rattus, Canis, Felis, Elephas, Equus.

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