Q.86 Which one of the following is an example of eumetazoans?
(A) Dictyostelium
(B) Hydra
(C) Sponges
(D) Volvox
Hydra is the only eumetazoan among the options, as it belongs to Cnidaria with true tissues, nerve nets, and gastrulation. The correct answer is (B) Hydra.
Eumetazoa Definition
Eumetazoans (= “true animals”) have organized tissues from germ layers, neurons/muscles, and gastrula-stage embryos—excluding sponges (Parazoa). All post-Cambrian phyla except Porifera.
Option Analysis
| Option | Organism | Kingdom/Phylum | Eumetazoan? | Reason |
|---|---|---|---|---|
| (A) Dictyostelium | Cellular slime mold | Protista (Amoebozoa) | NO | Acellular → multicellular via aggregation; no true tissues |
| (B) Hydra | Cnidarian polyp | Animalia (Cnidaria) | YES | Diploblastic: Ectoderm + endoderm + mesoglea; nerve net, cnidocytes |
| (C) Sponges | Porifera | Animalia (Porifera) | NO | Parazoan: Choanocytes, pinacocytes; no true tissues/germ layers |
| (D) Volvox | Colonial green alga | Protista (Chlorophyta) | NO | Colonial flagellates; no tissues/neurons |
Key Distinctions
Eumetazoa: Tissues → Organs → Body plan
↓ Cnidaria (Hydra), Bilateria (humans)
Parazoa: Cells → Functional syncytium (sponges)
Choanoflagellates → Protists (Dictyostelium, Volvox)Eumetazoans examples questions test true tissue organization—crucial for CSIR NET Life Sciences, GATE Biotechnology, and zoology grad students. Hydra (Cnidaria) represents eumetazoans with ectoderm-endoderm germ layers; sponges (Porifera) are parazoa without tissues.
Eumetazoa vs Parazoa vs Protista
Core Test: Does it have histological tissues (epithelial/mesenchymal layers)?
| Group | Tissue Type | Examples | CSIR NET Keywords |
|---|---|---|---|
| Eumetazoa | True tissues | Hydra, jellyfish, corals, bilaterians | Cnidaria, diploblastic |
| Parazoa | Cellular aggregates | Sponges (Porifera) | Choanocytes, osculum |
| Protista | None (colonial/acellular) | Dictyostelium (slime mold), Volvox (alga) | Amoebozoa, Chlorophyta |
Hydra Anatomy (Diploblastic Eumetazoan)
Ectoderm: Epidermis + cnidocytes + nerve net
Mesoglea: Acellular matrix
Endoderm: Gastrodermis + digestive cells
Gastrulation → 2 germ layers → true tissues.
Exam Traps Exposed
-
Sponges: “Multicellular animals” but asymmetrical, no tissues.
-
Dictyostelium: “Social amoeba”—temporary fruiting body, not permanent tissues.
-
Volvox: “Colonial alga”—flagellated cells in sphere, photosynthetic protist.
Phylogenetic Context
Choanoflagellates
↓
Porifera (sponges) ──┐
Eumetazoa (Hydra+) ── Ctenophora?
↓
Bilateria
Mnemonic: “EUMEtazoans = Every animal Under Man” (excl. sponges).
Related Searches: diploblastic triploblastic, parazoa eumetazoa difference, Hydra tissue organization, CSIR NET animal kingdom MCQs.
This eumetazoans examples guide equips biotechnology/zoology students for molecular biology entrance exams and evolutionary biology research. Master true tissues classification—ace your exam!
