🦁 Animal Kingdom

1. Basis of Classification

Animals are classified based on fundamental features like:

Levels of Organization: Cellular, Tissue, Organ, Organ-system.
Symmetry: Asymmetrical (Sponges), Radial (Coelenterates, Ctenophores, Adult Echinoderms), Bilateral (Annelids, Arthropods, etc.).
Diploblastic / Triploblastic: Presence of two (ectoderm, endoderm) or three germ layers (addition of mesoderm).
Coelom: Presence or absence of a body cavity lined by mesoderm. (Acoelomates, Pseudocoelomates, Coelomates).

Porifera (Sponges): Cellular level, water canal system, choanocytes.

Coelenterata (Cnidaria): Cnidoblasts (stinging cells), tissue level, polyp & medusa forms.

Ctenophora: Comb jellies, 8 ciliated comb plates, bioluminescence.

Platyhelminthes (Flatworms): Acoelomates, flame cells for excretion, parasites (Tapeworm).

Aschelminthes (Roundworms): Pseudocoelomates, muscular pharynx (Ascaris).

Annelida: Metameric segmentation, closed circulatory system (Earthworm).

Arthropoda: Largest phylum, jointed appendages, chitinous exoskeleton (Insects).

Mollusca: Second largest, soft body covered by calcareous shell, radula.

Echinodermata: Spiny skinned, water vascular system, tube feet (Starfish).

Hemichordata: Worm-like marine animals, stomochord (Balanoglossus).

Characterized by the presence of a Notochord, a dorsal hollow nerve cord, and paired pharyngeal gill slits.

Subphyla: Urochordata, Cephalochordata, and Vertebrata.

Agnatha (Cyclostomata): Jawless fishes (Lamprey).

Chondrichthyes: Cartilaginous fishes (Sharks).

Osteichthyes: Bony fishes (Rohu, Seahorse).

Amphibia: Dual life, moist skin, 3-chambered heart (Frog).

Reptilia: Creeping/crawling, dry cornified skin, mostly 3-chambered heart (Snake, Crocodile has 4).

Aves: Birds, feathers, forelimbs modified to wings, pneumatic bones, 4-chambered heart.

Mammalia: Mammary glands, hair, external ears (pinnae), viviparous.