NEET 2026: Animal Kingdom - Chordates & Non-Chordates Short Notes | Phylum-wise Summary

Animal Kingdom: Non-Chordates

4.2.1 Phylum – Porifera (Sponges)

• Common Name: Sponges
• Habitat: Generally marine and mostly asymmetrical
• Organisation: Primitive multicellular animals with cellular level of organisation
• Key System: Water transport or canal system with ostia, spongocoel and osculum
• Structural Lining: Choanocytes or collar cells line the canals
• Digestion: Intracellular
• Support: Skeleton of spicules or spongin fibres
• Sexuality: Hermaphrodite
• Examples: Sycon, Spongilla (Fresh water sponge), Euspongia

4.2.2 Phylum – Coelenterata (Cnidaria)

• Habitat: Aquatic, mostly marine
• Organisation: Tissue level, diploblastic
• Distinguishing Feature: Cnidoblasts or cnidocytes with nematocysts
• Body Forms: Polyp (sessile) and Medusa (free-swimming)
• Metagenesis: Alternation of generations in Obelia
• Examples: Physalia (Portuguese man-of-war), Adamsia, Meandrina

4.2.3 Phylum – Ctenophora (Comb Jellies)

• Common Name: Sea walnuts or comb jellies
• Habitat: Exclusively marine
• Locomotion: Eight external rows of ciliated comb plates
• Unique Property: Bioluminescence well-marked
• Reproduction: Sexual, external fertilization
• Examples: Pleurobrachia, Ctenoplana

4.2.4 Phylum – Platyhelminthes (Flatworms)

• Body Shape: Dorso-ventrally flattened
• Habitat: Mostly endoparasites
• Organisation: Organ level, triploblastic, acoelomate
• Excretion: Flame cells for osmoregulation
• Special Feature: Planaria possesses high regeneration capacity
• Examples: Taenia, Fasciola

4.2.5 Phylum – Aschelminthes (Roundworms)

• Body Shape: Circular in cross-section
• Organisation: Organ-system level, pseudocoelomate
• Alimentary Canal: Complete
• Sexuality: Dioecious, females longer than males
• Examples: Ascaris (Roundworm), Wuchereria, Ancylostoma

4.2.6 Phylum – Annelida (Segmented Worms)

• Organisation: Organ-system level, coelomate
• Segmentation: Metamerically segmented
• Key Systems:
  • Circulation: Closed circulatory system
  • Excretion: Nephridia
• Examples: Nereis, Pheretima, Hirudinaria

4.2.7 Phylum – Arthropoda

• Size: Largest phylum of Animalia
• Exoskeleton: Chitinous exoskeleton
• Limbs: Jointed appendages
• Key Systems:
  • Respiration: Gills, book lungs or tracheal system
  • Circulation: Open type
  • Excretion: Malpighian tubules
• Examples: Apis, Bombyx, Limulus (King crab - Living fossil)

4.2.8 Phylum – Mollusca

• Size: Second largest animal phylum
• Body: Unsegmented with head, muscular foot and visceral hump
• Feeding: Radula - rasping organ
• Examples: Pila, Pinctada, Octopus

4.2.9 Phylum – Echinodermata

• Name Origin: Endoskeleton of calcareous ossicles
• Habitat: All marine
• Symmetry: Adults radially symmetrical, larvae bilaterally symmetrical
• Distinguishing Feature: Water vascular system
• Excretion: Excretory system absent
• Examples: Asterias, Echinus, Cucumaria

4.2.10 Phylum – Hemichordata

• General: Worm-like marine animals
• Body Division: Proboscis, collar and long trunk
• Rudimentary Structure: Stomochord
• Excretion: Proboscis gland
• Examples: Balanoglossus, Saccoglossus

Animal Kingdom: Phylum Chordata

4.2.11 Phylum – Chordata (General Features)

• Fundamental Characteristics: Notochord, dorsal hollow nerve cord, paired pharyngeal gill slits
• Other Features: Post anal tail, closed circulatory system

Subphyla of Chordata (Protochordates)

• Urochordata: Notochord only in larval tail
• Cephalochordata: Notochord extends from head to tail
  • Examples: Branchiostoma (Amphioxus)

Subphylum – Vertebrata

• Defining Feature: Notochord replaced by vertebral column in adult
• Key Dictum: All vertebrates are chordates but all chordates are not vertebrates

4.2.11.1 Class – Cyclostomata

• General: Ectoparasites on some fishes
• Mouth: Sucking and circular without jaws
• Reproduction: Marine but migrate to fresh water for spawning
• Examples: Petromyzon, Myxine

4.2.11.2 Class – Chondrichthyes (Cartilaginous Fishes)

• Endoskeleton: Cartilaginous
• Buoyancy: Absence of air bladder - swim constantly
• Special Organs: Electric organs, poison sting
• Examples: Scoliodon, Trygon

4.2.11.3 Class – Osteichthyes (Bony Fishes)

• Endoskeleton: Bony
• Buoyancy: Air bladder present regulates buoyancy
• Examples: Exocoetus, Labeo, Hippocampus

4.2.11.4 Class – Amphibia

• Habitat: Aquatic and terrestrial
• Respiration: Gills, lungs, and through skin
• Heart: Three-chambered
• Examples: Rana, Bufo, Ichthyophis

4.2.11.5 Class – Aves (Birds)

• Defining Feature: Feathers
• Endoskeleton: Hollow bones with air cavities (pneumatic)
• Temperature: Homoiothermous (warm-blooded)
• Respiration: Air sacs connected to lungs
• Examples: Columba, Struthio, Pavo

4.2.11.6 Class – Mammalia

• Unique Feature: Milk producing glands (mammary glands)
• Skin: Hair, external ears
• Teeth: Heterodont dentition
• Heart: Four-chambered
• Examples: Ornithorhynchus (Platypus - egg-laying), Macropus, Panthera tigris