Part 2 — Porifera to Nematoda: Structure, Life Cycle & Ecology (Q.26–50)

Part 2 — Porifera to Nematoda: Structure, Life Cycle & Ecology (Q.26–50)

Q26. The ascon, sycon, and leucon types describe:

A) Body forms of cnidarians
B) Canal systems in sponges
C) Nervous systems of flatworms
D) Feeding types of molluscs
Answer: B
Explanation:
A) Cnidarians have polyp/medusa.
B) Correct — three types of sponge canal systems (increasing complexity).
C/D) Not related.

Q27. Gemmules are reproductive/resistant structures produced by:

A) Cnidarians
B) Some fresh-water and marine sponges (Porifera) and some sponges in cold climates
C) Flatworms
D) Nematodes
Answer: B
Explanation:
A) Cnidarians don’t form gemmules.
B) Correct — gemmules are internal buds/overwintering structures of some sponges.
C/D) Incorrect.

Q28. Which class of Cnidaria typically has dominant medusa stage?

A) Hydrozoa
B) Scyphozoa
C) Anthozoa
D) Porifera
Answer: B
Explanation:
A) Hydrozoa often have both stages but polyp dominant in some.
B) Correct — scyphozoans (true jellyfish) have large medusa stage.
C) Anthozoa are only polyps (sea anemones, corals).
D) Porifera is separate phylum.

Q29. Planarian excretion is by:

A) Flame cells and protonephridia
B) Nephridia of annelids
C) Metanephridia
D) Malpighian tubules
Answer: A
Explanation:
A) Correct — flatworms like planaria use protonephridial flame cells.
B/C) Annelid excretory structures.
D) Insects and some arthropods.

Q30. Tapeworms (Cestoda) lack:

A) Digestive system (gut)
B) Reproductive organs
C) Scolex (attachment organ)
D) Segmentation (they are not segmented)
Answer: A
Explanation:
A) Correct — cestodes absorb nutrients across body wall, lack digestive tract.
B) False — they are highly reproductive.
C) Scolex present for attachment.
D) They are segmented into proglottids.

Q31. Nematode cuticle is:

A) Chitinous and molted during growth
B) Composed of living epidermis only
C) Not molted; permanent
D) Made of cellulose
Answer: A
Explanation:
A) Correct — nematodes have a collagenous cuticle that molts (ecdysis).
B) Cuticle is non-cellular.
C) Cuticle is periodically shed.
D) Cellulose not in nematode cuticle.

Q32. Ascaris lumbricoides is a:

A) Free-living nematode
B) Parasite causing ascariasis in humans
C) Flatworm parasite
D) Protozoan parasite
Answer: B
Explanation:
A) Ascaris is parasitic.
B) Correct — intestinal roundworm causing ascariasis.
C) Not a flatworm.
D) Not a protozoan.

Q33. Which phylum includes organisms with radial canals and cnidocytes?

A) Porifera
B) Cnidaria
C) Platyhelminthes
D) Arthropoda
Answer: B
Explanation:
A) Porifera lack cnidocytes.
B) Correct — cnidarians possess cnidocytes/nematocysts and radial canals in some medusae.
C/D) No cnidocytes.

Q34. In nematodes, body cavity is termed:

A) True coelom
B) Pseudocoelom
C) Acoelomate
D) Hemocoel
Answer: B
Explanation:
A) False — not true coelom.
B) Correct — pseudocoelom located between mesoderm and endoderm.
C) Acoelomate lacks cavity.
D) Hemocoel is open body cavity of arthropods.

Q35. Schistosoma (blood flukes) belong to which phylum/class?

A) Platyhelminthes, Trematoda
B) Nematoda, Secernentea
C) Cestoda
D) Annelida
Answer: A
Explanation:
A) Correct — Schistosoma are trematode flukes (flatworms).
B/C/D) Incorrect.

Q36. Which structure is characteristic of Cnidaria for capturing prey?

A) Choanocyte
B) Nematocyst (stinging capsule)
C) Radula
D) Parapodia
Answer: B
Explanation:
A) Choanocyte — sponges.
B) Correct — nematocysts in cnidocytes sting prey.
C) Radula — molluscan organ.
D) Parapodia — annelids.

Q37. The life cycle of many trematodes involves:

A) One host only
B) Multiple hosts including molluscan intermediate host
C) Only plants as hosts
D) No intermediate hosts
Answer: B
Explanation:
A) Many require intermediate hosts.
B) Correct — e.g., liver fluke uses snail intermediate.
C/D) Incorrect.

Q38. Nematodes differ from annelids mainly because nematodes:

A) Are segmented
B) Have jointed appendages
C) Lack segmentation and have a pseudocoelom
D) Have closed circulatory system
Answer: C
Explanation:
A) Annelids are segmented.
B) Arthropods have jointed appendages.
C) Correct — nematodes are unsegmented and pseudocoelomate.
D) Closed circulation is in annelids; nematodes lack it.

Q39. Which of these is a free-living flatworm used in regeneration studies?

A) Taenia solium
B) Planaria (Dugesia)
C) Fasciola hepatica
D) Wuchereria bancrofti
Answer: B
Explanation:
A/C are parasitic flukes/cestodes.
B) Correct — planaria exhibit remarkable regeneration.
D) Wuchereria is a nematode.

Q40. The excretory/osmoregulatory system in freshwater planaria is adapted by:

A) Metanephridia only
B) Flame cells and protonephridia to expel excess water
C) Kidneys as in vertebrates
D) Malpighian tubules
Answer: B
Explanation:
A) Metanephridia are in annelids.
B) Correct — flame cells flagella drive fluid out to regulate osmotic balance.
C/D) Vertebrate kidneys and insect tubules are absent.

Q41. Nematode larvae migrate through human tissues in which disease?

A) Malaria
B) Ascariasis and filariasis (depending on species)
C) Amoebiasis
D) Tuberculosis
Answer: B
Explanation:
A) Malaria is protozoan.
B) Correct — e.g., Ascaris larvae migrate; Wuchereria in lymphatics.
C/D) Bacterial/protozoan, not nematode.

Q42. The main developmental difference between planula (cnidarian) and miracidium (trematode) is:

A) Both are adult forms
B) Planula is a free-swimming larva produced by cnidarian, miracidium is parasitic larval stage of fluke adapted to find snail host
C) Both are spore stages of fungi
D) Both are pupal stages of insects
Answer: B
Explanation:
A/C/D) Not true.
B) Correct — planula and miracidium are larval stages with different ecological roles.

Q43. Which of the following is NOT a characteristic of nematodes?

A) Bilateral symmetry
B) Triploblastic organization
C) Segmented body with parapodia
D) Pseudocoelomic cavity
Answer: C
Explanation:
A/B/D) True of nematodes.
C) False — nematodes lack segmentation and parapodia (found in annelids).

Q44. The simplest nervous system is found in:

A) Annelids with ventral nerve cord and ganglia
B) Sponges which lack true nervous tissue
C) Arthropods with complex brains
D) Vertebrates with centralized brains
Answer: B
Explanation:
A/C/D) More complex systems.
B) Correct — sponges lack neurons; signal conduction via syncitial cells in some.

Q45. Why are nematodes important in soil ecology?

A) They make soil sandy
B) They are decomposers and help nutrient cycling (some are bacterivores, fungivores, predators)
C) They produce oxygen
D) They fix atmospheric nitrogen
Answer: B
Explanation:
A/C/D) Incorrect.
B) Correct — nematodes influence microbial populations and nutrient turnover.

Q46. In tapeworms, the proglottids are:

A) Sensory organs
B) Reproductive segments each with male and female organs (hermaphroditic)
C) Feeding appendages
D) Larval forms
Answer: B
Explanation:
A/C/D) Incorrect.
B) Correct — proglottids contain reproductive systems and can be gravid.

Q47. Which is an adaptation of parasitic flatworms for parasitism?

A) Presence of digestive tract for independent feeding
B) Complex attachment organs (suckers/hooks), protective tegument, reproductive capacity
C) Wings for dispersal
D) Photosynthetic pigments
Answer: B
Explanation:
A) Many parasitic flatworms lack digestive tract.
B) Correct — adaptations to survive in host environment.
C/D) Not relevant.

Q48. The function of pseudocoelom in nematodes does NOT include:

A) Acting as hydrostatic skeleton
B) Distribution of nutrients and wastes
C) Forming true mesoderm-lined organs
D) Providing space for organs
Answer: C
Explanation:
A/B/D) True roles of pseudocoelom.
C) False — pseudocoelom not fully mesoderm-lined, so organs aren’t in true coelomic cavity.

Q49. Which of these is an example of a parasitic nematode causing elephantiasis?

A) Ascaris lumbricoides
B) Wuchereria bancrofti
C) Taenia solium
D) Schistosoma mansoni
Answer: B
Explanation:
A) Ascaris causes intestinal ascariasis.
B) Correct — Wuchereria causes lymphatic filariasis (elephantiasis).
C) Taenia is a cestode.
D) Schistosoma is a trematode.

Q50. In freshwater sponges, osmoregulatory balance is maintained by:

A) Contractile vacuoles are not typical; water is expelled via oscula and aquiferous system; structural adaptations and amoebocytes help manage excess water
B) Lungs
C) Kidneys
D) Malpighian tubules
Answer: A
Explanation:
B–D) Not applicable.
A) Correct — sponges manage water flow via choanocytes, oscula and special cells. (more…)