1.4 The Animal Kingdom

Basis of Classification

• Levels of Organisation: Cellular, Tissue, Organ, Organ System.
• Symmetry: Asymmetrical, Radial, Bilateral.
• Germ Layers: Diploblastic, Triploblastic.
• Coelom: Acoelomate, Pseudocoelomate, Coelomate.
• Segmentation: Metamerism.

Non-Chordata (Invertebrates)

• Phylum Porifera: Cellular level, canal system (e.g., Sponges).
• Phylum Cnidaria: Tissue level, cnidoblasts, polyp/medusa forms (e.g., Jellyfish, Corals).
• Phylum Ctenophora: Tissue level, comb plates, bioluminescence (e.g., Comb Jellies).
• Phylum Platyhelminthes: Organ level, acoelomate, flame cells (e.g., Flatworms).
• Phylum Nematoda: Organ system level, pseudocoelomate (e.g., Roundworms).

Non-Chordata (Continued)

• Phylum Annelida: Metameric segmentation, closed circulatory system (e.g., Earthworms).
• Phylum Arthropoda: Chitinous exoskeleton, jointed appendages, open circulatory system (e.g., Insects, Spiders).
• Phylum Mollusca: Soft body with a calcareous shell, muscular foot, radula (e.g., Snails, Octopus).
• Phylum Echinodermata: Spiny skin, water vascular system, radial symmetry in adults (e.g., Starfish).
• Phylum Hemichordata: Worm-like, stomochord (e.g., Acorn worms).

Chordata

• Key Features: Notochord, dorsal hollow nerve cord, pharyngeal gill slits, post-anal tail.

• Subphylum Urochordata: Notochord in larval tail (e.g., Sea squirts).

• Subphylum Cephalochordata: Notochord from head to tail (e.g., Lancelets).

• Subphylum Vertebrata: Notochord replaced by vertebral column.

Vertebrata: Fishes and Amphibians

• Class Cyclostomata: Jawless, sucking circular mouth (e.g., Lampreys).
• Class Chondrichthyes: Cartilaginous skeleton, placoid scales (e.g., Sharks, Rays).
• Class Osteichthyes: Bony skeleton, air bladder (e.g., Tuna, Salmon).
• Class Amphibia: Live on land and in water, moist skin (e.g., Frogs, Salamanders).

Vertebrata: Reptiles, Birds, and Mammals

• Class Reptilia: Dry scaly skin, lay eggs on land (e.g., Lizards, Snakes, Crocodiles).
• Class Aves: Feathers, forelimbs modified into wings, pneumatic bones (e.g., Birds).
• Class Mammalia: Mammary glands, hair, external ears (e.g., Humans, Whales, Bats).