Chapter 4 / 4.2 Classification of Animals

Animal Kingdom Classification Notes 🌍🐾

Key NEET Concepts 🎯

• Coelom types (acoelomate/pseudocoelomate/coelomate)
• Chordate features (notochord, dorsal nerve cord, gill slits)
• Vertebrate classes (differences in heart chambers, reproduction)

Basic Classification Features 🔑

Germ layers:
– Diploblastic = 2 layers (ectoderm + endoderm)
– Triploblastic = 3 layers (ectoderm + mesoderm + endoderm)

Coelom (body cavity): 🌡️
– Coelomate: True cavity lined by mesoderm (e.g., earthworms, humans)
– Pseudocoelomate: Cavity not fully lined by mesoderm (e.g., roundworms)
– Acoelomate: No cavity (e.g., flatworms)

Notochord: 🦴
– Rod-like structure in embryos
– Present → Chordates
– Absent → Non-chordates

Major Animal Phyla 🐚🦋

1. Porifera (Sponges)

• 🧽 Marine, asymmetrical bodies
• 🕳️ Water enters through ostia, exits through osculum
• 🚫 No tissues/organs (cellular organization)
• ✨ Examples: Sycon, Spongilla (freshwater)

2. Coelenterata/Cnidaria

• ☠️ Stinging cells called cnidoblasts
• 🌊 Aquatic, radial symmetry
• 🎭 Two forms: polyp (stationary) and medusa (swimming)
• ✨ Examples: Jellyfish, corals

3. Platyhelminthes (Flatworms)

• 📏 Flattened bodies, acoelomate
• 🪝 Parasites have hooks/suckers
• 🔥 Excrete via flame cells
• ✨ Examples: Tapeworm, liver fluke

4. Aschelminthes (Roundworms)

• ⚪ Circular cross-section, pseudocoelomate
• 🚻 Separate sexes (males smaller)
• ✨ Examples: Ascaris, hookworm

5. Annelida (Segmented worms)

• ➰ Metameric segmentation (body rings)
• 💧 Nephridia for excretion
• ❤️ Closed circulatory system
• ✨ Examples: Earthworm, leech

6. Arthropoda

• 🦐 Largest phylum (insects, crustaceans)
• 🦴 Chitinous exoskeleton
• 🦿 Jointed appendages
• ✨ Examples: Butterflies, spiders, crabs

7. Mollusca

• 🐚 Soft body, often with shell
• 👅 Feeds using radula (file-like tongue)
• ✨ Examples: Snails, octopus, oysters

8. Echinodermata

• ⭐ Spiny skin, radial symmetry
• 💦 Unique water vascular system
• ✨ Examples: Starfish, sea urchins

9. Hemichordata

• 🐛 Worm-like, marine
• 🔗 Rudimentary stomochord
• ✨ Example: Balanoglossus

Phylum Chordata 🐠🐒

Defining features:
1. Notochord
2. Dorsal hollow nerve cord
3. Paired pharyngeal gill slits
4. Post-anal tail

Vertebrate Classes:

Cyclostomata (Jawless fish):
– 🐍 Eel-like, no scales (e.g., lamprey)
– 🩸 Parasites on fish

Chondrichthyes (Cartilaginous fish):
– 🦈 Cartilage skeleton (e.g., shark)
– ⚡ Some have electric organs

Osteichthyes (Bony fish):
– 🐟 Bony skeleton, air bladder
– ✨ Examples: Tuna, seahorse

Amphibia:
– 🌊💨 Live in water & land (e.g., frogs)
– 👂 Tympanum as ear
– ❤️ 3-chambered heart

Reptilia:
– 🦎 Dry scaly skin (e.g., snakes)
– 🥚 Internal fertilization, lay eggs
– ❤️ Crocodiles have 4-chambered heart

Aves (Birds):
– 🪶 Feathers, beak
– ✈️ Hollow bones for flight
– 🔥 Warm-blooded

Mammalia:
– 🍼 Mammary glands
– 🧔 Hair/fur, external ears
– 👶 Mostly give live birth
– ✨ Examples: Bats, whales, humans

Quick Comparison Table 📊

💡 Remember: Chordates have all 4 key features at some life stage!