Kingdom Classification - Animalia

Characteristics

• Multicellular: Organisms in this kingdom are composed of many cells.
• Eukaryotic: They possess a true nucleus and other membrane-bound organelles.
• Heterotrophic: They obtain nutrients by ingesting other organisms or organic matter.
• No Cell Wall: Animal cells do not have a cell wall.
• Motility: Most animals are capable of locomotion.
• Reproduction: Primarily reproduce sexually.

(a) Vertebrates

Vertebrates are animals that possess a backbone or spinal column.

• Key Characteristics:

  • Presence of a vertebral column (backbone).
  • Well-developed internal skeleton.
  • Complex nervous system with a brain enclosed in a cranium.
  • Bilateral symmetry.
  • Closed circulatory system.

• Examples: Fish, Amphibians, Reptiles, Birds, Mammals.

(b) Invertebrates

Invertebrates are animals that do not possess a backbone or spinal column. They constitute the vast majority of animal species.

9 Major Phyla

1. Porifera (Sponges):
   • Characteristics: Simplest multicellular animals, sessile, porous body, filter feeders.
   • Example: Sponges (e.g., Sycon).
2. Cnidaria (Coelenterata):
   • Characteristics: Radial symmetry, stinging cells (cnidocytes), sac-like body with a single opening (mouth/anus).
   • Example: Jellyfish, Hydra, Sea Anemones, Corals.
3. Platyhelminthes (Flatworms):
   • Characteristics: Dorsoventrally flattened body, bilateral symmetry, acoelomate (no body cavity), parasitic or free-living.
   • Example: Tapeworms, Planaria, Liver Fluke.
4. Nematoda (Roundworms):
   • Characteristics: Cylindrical, unsegmented body, pseudocoelomate (false body cavity), many are parasitic.
   • Example: Ascaris, Filarial worms.
5. Annelida (Segmented Worms):
   • Characteristics: Segmented body, true coelom, well-developed organ systems.
   • Example: Earthworms, Leeches.
6. Arthropoda:
   • Characteristics: Jointed legs, chitinous exoskeleton, segmented body, most diverse phylum.
   • Example: Insects (e.g., Cockroach, Butterfly), Spiders, Crabs.
7. Mollusca:
   • Characteristics: Soft body, usually protected by a shell, muscular foot, mantle.
   • Example: Snails, Clams, Octopuses.
8. Echinodermata:
   • Characteristics: Spiny skin, radial symmetry (in adults), water vascular system.
   • Example: Starfish, Sea Urchins.