Kingdom: Animalia - SS1 Biology Lesson Note

Animals, belonging to the kingdom Animalia, are classified into several major divisions or phyla based on their evolutionary relationships and distinct characteristics. Here are some of the main divisions of animals:

1. Porifera (Sponges): Sponges are simple, multicellular animals characterized by their porous body structure. They lack tissues and organs and are filter feeders, obtaining nutrients from water circulating through their bodies.

2. Cnidaria (Jellyfish, Corals, and Sea Anemones): Cnidarians are aquatic animals that exhibit radial symmetry and possess specialized stinging cells called cnidocytes. They include jellyfish, corals, sea anemones, and hydroids.

3. Platyhelminthes (Flatworms): Flatworms are soft-bodied, unsegmented animals with a flattened body shape. They can be free-living or parasitic, and examples include planarians and tapeworms.

4. Nematoda (Roundworms): Roundworms are cylindrical, unsegmented animals found in diverse habitats. They have a complete digestive system and can be free-living or parasitic. Examples include soil-dwelling nematodes and parasitic worms causing diseases in humans and animals.

5. Annelida (Segmented Worms): Annelids are segmented worms characterized by their body segmentation. They include earthworms, leeches, and marine polychaetes.

6. Arthropoda (Insects, Crustaceans, Arachnids, and Others): Arthropods are the largest animal phylum and have jointed appendages, segmented bodies, and exoskeletons. They include insects, spiders, crustaceans (such as crabs and shrimp), and millipedes.

7. Mollusca (Mollusks): Mollusks are soft-bodied animals often protected by a hard shell. They include snails, clams, squids, and octopuses.

8. Echinodermata (Sea Stars, Sea Urchins, and Sea Cucumbers): Echinoderms are marine animals characterized by radial symmetry and a spiny exoskeleton. They include sea stars, sea urchins, and sea cucumbers.

9. Chordata (Chordates): Chordates are a diverse group of animals characterized by the presence of a notochord (a flexible, rod-like structure) at some point in their development. Chordates include fish, amphibians, reptiles, birds, and mammals, including humans.

The first eight are invertebrates (without backbone) while Chordata are vertebrates (with backbone).

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