MCQs on Invertebrates

Invertebrates are animals that do not have or develop a vertebral column (also known as a backbone or spine), which is developed from the notochord. Apart from the chordate subphylum Vertebrata, this comprises all animals. Arthropods (insects, arachnids, crustaceans, and myriapods), molluscs (chitons, snails, bivalves, squids, and octopuses), annelids (earthworms and leeches), and cnidarians are all examples of invertebrates (hydras, jellyfishes, sea anemones, and corals). Tunicata and Cephalochordata, for example, are more closely linked to vertebrates than other invertebrates. As a result, invertebrates are paraphyletic, and the term has no taxonomic significance.

Q1. Flagellated cells, that lines the spongocoel in Poriferans are referred to as

1. Ostia

2. Mesenchymal cells

3. Oscula

4. Choanocytes

Ans. Here the correct answer is option ‘4’ choanocytes. Choanocytes (also known as “collar cells”) are sponge cells with a central flagellum, or cilium, surrounded by a collar of microvilli joined by a thin membrane that line the inside of the asconoid.

Q2. Which among the following is not a characteristic of the phylum Arthropoda?

1. Parapodia

2. Metameric segmentation

3. Jointed appendages

4. Chitinous exoskeleton

Ans. The correct answer is option ‘1’ parapodia. Parapodia are the basic locomotion organs that are used in both creeping and swimming. They also help with respiration because they are extremely vascularized. These structures can be seen in members of phylum Annelida.

Q3. Which of the following is an example of bilaterally symmetrical and triploblastic animal

1. Cnidarians

2. Roundworms

3. Sponges

4. Ctenophores

Ans. The correct answer is option ‘3’ roundworms. 

Q4. Phylum Annelida is not characterized by which of the following

1. Segmentation

2. Closed circulatory system

3. Pseudocoelom

4. Ventral nerve cord

Ans. The correct answer is option ‘3’ pseudocoelom. The pseudocoelom is a fluid-filled body cavity that lies inside the nematode’s external body wall and bathes the internal organs, including the alimentary and reproductive systems. It’s a nematode-like fake body cavity. The second body cavity is another name for it.

Q5. Which among the following possess notochord in the embryonic stage?

1. Non-chordates

2. Vertebrates

3. Some of the chordates

4. All chordates

Ans. The correct answer is option ‘4’ all chordates. 

Q6. An important characteristic feature, which is present only in the phylum Coelenterata is

1. Flame cells

2. Nematocysts

3. Hermaphroditism

4. Polymorphism

Ans. Here, the correct answer is option ‘2’ nematocysts. The nematocyst is a small, elongated, or spherical capsule generated solely by Cnidaria (e.g., jellyfish, corals, sea anemones). Several of these capsules can be seen on the body’s surface. Each is made by a cnidoblast cell and contains a coiled, hollow, generally barbed thread that, when stimulated, swiftly rotates outward (i.e., is everted) from the capsule.

Q7. Cnidarians, which possess only polyp stage

1. Cubozoa

2. Scyphozoa

3. Hydrozoa

4. Anthozoa

Ans. The correct answer is option ‘4’ anthozoa. Sea anemones, stony corals, and soft corals all are members of the Anthozoa class of marine invertebrates. The polyp, which is made up of a cylindrical column capped by a disc with a central mouth encircled by tentacles, is the basic unit of the adult.

Q8. Which of the following structures helps in the excretion of flatworms.

1. Protonephridia

2. Green glands

3. Flame cells

4. Malpighian tubules

Ans. The correct answer is option ‘3’ flame cells. A flame cell is a specialised excretory cell found in the smallest freshwater invertebrates, such as flatworms, rotifers, and nemerteans; it is the simplest excretory system identified in any animal. The waste-removing function of flame cells is similar to that of a kidney. Protonephridia are clusters of flame cells.

Q9. The group of molluscs, that exhibit eyes similar to vertebrates

1. Bivalvia

2. Cephalopoda

3. Gastropoda

4. Pelecypoda

Ans. The correct answer is option ‘2’ cephalopoda. 

Explanation: Cephalopoda is a molluscan clade with eyes that mimic vertebrate eyes.

Q10. Tube feet are found in

1. Starfish

2. Cuttlefish

3. Crayfish

4. Jellyfish

Ans. The correct answer is option ‘1’ starfish. Tube feet (technically podia) are small active tubular projections on the oral face of an echinoderm, such as the arms of a starfish or the undersides of sea urchins, sand dollars, and sea cucumbers; they are more discrete on brittle stars, though they are present, and have only a feeding function in feather stars. They are a part of the vascular system of the water. 

Q11. Which among the following accurately defines “Mother-of-pearl”?

1. An oyster which yields the pearl

2. A special large sized pearl found in Japan

3. Female individual of certain species of shelled mollusc

4. A hard iridescent substance forming the inner layer of certain shell

Ans. The correct option is ‘4’ a hard iridescent substance forming the inner layer of a certain shell.

Q12. Periplaneta belongs to which phylum?

1. Arthropoda

2. Mollusca

3. Annelida

4. Echinodermata

Ans. The correct answer here is option ‘1’ Arthropoda. 

Explanation: It is classified as a member of the Phylum Arthropoda since it has an exoskeleton, segmented bodies, joined appendages, bilateral symmetry, and an open circulatory system.

Q13. Radial symmetry is found in which of the following

1. Coelenterata and Platyhelminthes

2. Arthropoda and Mollusca

3. Coelenterata and Echinodermata

4. Porifera and Coelenterata

Ans. The correct answer is option ‘3’ coelenterata and echinodermata. A symmetry in which the sides demonstrate correspondence or regularity of components around a central axis is known as radial symmetry. In contrast to bilateral symmetry, which is more prevalent than radial symmetry, radial symmetry is less common. The majority of animals have bilateral symmetry, which means they have a left and right side along the midline. Radial symmetry is found in a relatively small number of animals.

Q14. Which of the following helps in the development of canal system in sponges  

1. Porous walls

2. Folding of inner walls

3. Gastrovascular system

4. Reproduction

Ans. Here the answer is option ‘2’ folding of inner walls. The phylum Porifera is distinguished by the water circulatory system of sponges, often known as the canal system. Aquiferous system is another name for canal system. The sponge canal system aids in food uptake, respiratory gas exchange, and excretion. The fundamental constituents of the canal system are the numerous perforations on the body surface of the sponges allowing admission and outflow of water current.