Non-chordate phyla
| Phylum | Diagnostic feature | Example |
|---|---|---|
| Porifera | Pores, spicules | Sponge |
| Cnidaria | Nematocysts (stinging cells) | Hydra, jellyfish |
| Platyhelminthes | Flat, acoelomate | Planaria, tapeworm |
| Nematoda | Round, pseudocoelomate | Ascaris |
| Annelida | Segmented, nephridia | Earthworm |
| Arthropoda | Jointed legs, exoskeleton, largest phylum | Cockroach, prawn |
| Mollusca | Soft body, mantle, shell | Snail, octopus |
| Echinodermata | Water vascular system, spiny skin | Starfish |
Chordate hallmarks
Phylum Chordata shows, at some stage: a notochord, a dorsal hollow nerve cord, pharyngeal gill slits, and a post-anal tail.
Symmetry & body cavity
- Radial symmetry: Cnidaria, Echinodermata (adult).
- Bilateral symmetry: most others.
- Coelom: true body cavity — Annelida onward.
Focus on the one feature that uniquely identifies each phylum — that's how MECEE frames these questions.