📚 Basis of Classification
🔹 Level of organization – Cellular, Tissue, Organ, Organ system
🔹 Symmetry – Asymmetrical (e.g. Sponges), Radial (e.g. Cnidaria), Bilateral (e.g. Platyhelminthes to Chordates)
🔹 Germ layers – Diploblastic (2 layers), Triploblastic (3 layers)
🔹 Body cavity (Coelom) – Acoelomate, Pseudocoelomate, Coelomate
🔹 Segmentation – Present in Annelids, Arthropods, etc.
🔹 Notochord – Present only in Chordates
1️⃣ Porifera (Sponges)
✅ Pore-bearing, asymmetrical
✅ Cellular level of organization
✅ Canal system, Choanocytes
✅ Skeleton: spicules/spongin
🔸 Example: Sycon, Spongilla, Euspongia
2️⃣ Cnidaria (Coelenterata)
✅ Radial symmetry, diploblastic
✅ Tissue level organization
✅ Cnidoblasts (stinging cells), Gastrovascular cavity
✅ Polyp & Medusa forms
🔸 Example: Hydra, Jellyfish, Sea Anemone
3️⃣ Ctenophora (Comb jellies)
✅ Radial symmetry, diploblastic
✅ 8 comb plates for locomotion
✅ Bioluminescence
🔸 Example: Pleurobrachia, Ctenoplana
4️⃣ Platyhelminthes (Flatworms)
✅ Bilateral symmetry, triploblastic, acoelomate
✅ Dorsoventrally flattened body
✅ Mostly parasitic
🔸 Example: Planaria, Taenia (Tapeworm), Fasciola (Liver fluke)
5️⃣ Aschelminthes (Roundworms)
✅ Pseudocoelomate, bilateral symmetry
✅ Complete digestive tract
✅ Unisexual
🔸 Example: Ascaris, Wuchereria
6️⃣ Annelida (Segmented worms)
✅ Metameric segmentation
✅ Coelomate, closed circulatory system
✅ Nephridia for excretion
🔸 Example: Earthworm, Leech, Nereis
7️⃣ Arthropoda – Largest phylum
✅ Jointed appendages, segmented body
✅ Open circulatory system
✅ Exoskeleton of chitin
🔸 Example: Cockroach, Prawn, Butterfly, Spider
8️⃣ Mollusca
✅ Second largest phylum
✅ Soft body with calcium carbonate shell
✅ Unsegmented body – head, foot, visceral mass
🔸 Example: Pila, Octopus, Unio
9️⃣ Echinodermata
✅ Spiny-skinned, marine, radial symmetry (adult)
✅ Water vascular system for movement
✅ Endoskeleton of calcium carbonate
🔸 Example: Starfish, Sea urchin, Sea cucumber
🔟 Chordata – Presence of notochord (at some stage)
✅ Dorsal hollow nerve cord
✅ Pharyngeal gill slits
✅ Post-anal tail
✅ Closed circulatory system
Subphyla:
- Urochordata – Herdmania
- Cephalochordata – Amphioxus
- Vertebrata – True vertebral column & skull
Vertebrates (Major Classes):
- Pisces – Fishes
- Amphibia – Frogs, Toads
- Reptilia – Snakes, Lizards
- Aves – Birds (Feathers, beak, flight)
- Mammalia – Hair, Mammary glands, Viviparous (mostly)
🌟 Important Points
📌 Metamerism – Seen in Annelids, Arthropods, Chordates
📌 Pseudocoelom – Only in Aschelminthes
📌 Notochord – Exclusive to Chordates
📌 Open circulatory system – Arthropoda, Mollusca
📌 Water vascular system – Echinodermata