Animal Kingdom: Basis of Classification

📊 4.1 Basis of Classification

Animals look super different, but scientists group them using shared features like:

  • How cells are arranged
  • Body symmetry
  • Type of body cavity (coelom)
  • Digestive/circulatory/reproductive systems

🔬 4.1.1 Levels of Organisation

  • Cellular level (e.g., sponges):
    Cells work loosely together like a team 👯
  • Tissue level (e.g., coelenterates):
    Cells form tissues for specific jobs 🧪
  • Organ level (e.g., flatworms):
    Tissues make organs (e.g., stomach) 💚
  • Organ system level (e.g., humans):
    Organs team up for big tasks (e.g., digestive system) 🤝

⚖️ 4.1.2 Symmetry

  • Asymmetrical: No symmetry (e.g., sponges) 🌀
  • Radial symmetry: Cut like a pizza � into equal halves (e.g., jellyfish)
  • Bilateral symmetry: Only 1 cut 🤏 gives mirror halves (e.g., insects)

🍰 4.1.3 Germ Layers

  • Diploblastic: 2 layers
    (Ectoderm + Endoderm + jelly-like mesoglea) → e.g., jellyfish 🪸
  • Triploblastic: 3 layers
    (Ectoderm + Mesoderm + Endoderm) → e.g., worms to humans 👶

🕳️ 4.1.4 Coelom (Body Cavity)

  • Coelomates: True cavity lined by mesoderm
    (e.g., earthworms, humans) 👍
  • Pseudocoelomates: Fake cavity with scattered mesoderm
    (e.g., roundworms) ⚠️
  • Acoelomates: No cavity
    (e.g., flatworms) ❌

🔗 4.1.5 Segmentation

Body divided into repeating segments (e.g., earthworm’s rings 🪱).
Called metamerism.

🦴 4.1.6 Notochord

  • Chordates: Have a backbone-like rod (notochord) during development 🐣→🐟→🐒
  • Non-chordates: No notochord (e.g., starfish, snails) ⭐

🗂️ 4.2 Classification of Animals

Scientists group animals based on all these features!

💡 NEET Super-Important Concepts

  1. Symmetry types (radial vs. bilateral)
  2. Germ layers (diplo vs. triploblastic)
  3. Coelom types (coelomate/pseudo/acoelomate)
  4. Notochord (chordate vs. non-chordate)
  5. Organisation levels (cellular → organ system)

Keep practicing – you’re mastering animal diversity! 🐢🐅🐌