1. Porifera (Sponges):
- Sessile, filter-feeding organisms.
- Lack organized tissues and organs.
- Examples include sea sponges and glass sponges.
2. Cnidaria (Jellyfish and Sea Anemones):
- Radially symmetrical aquatic animals.
- Have a gastrovascular cavity and stinging cells called nematocysts.
- Examples include jellyfish, corals, and sea anemones.
3. Platyhelminthes (Flatworms):
- Dorsoventrally flattened, bilaterally symmetrical animals.
- Lack a body cavity.
- Examples include tapeworms, flukes, and planarians.
4. Nematoda (Roundworms):
- Unsegmented, cylindrical worms with a pseudocoelom (body cavity).
- Found in a wide range of habitats.
- Examples include parasitic worms like hookworms and pinworms, as well as free-living nematodes in soil and water.
5. Annelida (Segmented Worms):
- Bilaterally symmetrical, segmented worms with a true coelom.
- Examples include earthworms, leeches, and segmented polychaetes like Nereis.
6. Mollusca (Shellfish, Snails, and Octopi):
- Bilaterally symmetrical, soft-bodied animals with a radula (feeding structure) and a mantle (secretes a shell in some species).
- Examples include clams, snails, squids, and octopi.
7. Arthropoda (Insects, Spiders, and Crustaceans):
- The largest and most diverse animal phylum.
- Have jointed appendages and a segmented body.
- Examples include insects (ants, butterflies), spiders, crabs, and lobsters.
8. Echinodermata (Starfish, Sea Urchins, and Sea Cucumbers):
- Marine organisms with a unique water vascular system and radial symmetry.
- Examples include starfish, sea urchins, and sea cucumbers.
9. Chordata (Vertebrates and Tunicates):
- Animals with a notochord, dorsal nerve cord, pharyngeal slits, and a post-anal tail (at some stage of their life cycle).
- Includes fish, amphibians, reptiles, birds, and mammals.
These major groups represent the main divisions of the animal kingdom, providing a broad framework for classifying and studying the immense diversity of animal life.