Animal Kingdom – Basis of Classification of Animals: NEET MCQs with Answers

15 free questions on Animal Kingdom – Basis of Classification of Animals for NEET (UG), starting with previous-year NEET and AIPMT questions. Try each one, then tap Show answer for the answer and a short explanation.

Syllabus covered: Basis of Classification of Animals: Salient features and classification of animals

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Question 1

Previous-year question
Which pair is incorrectly matched? [Re-NEET 2024]
  1. Annelids and arthropods – Bilateral symmetry
  2. Sponges – Acoelomates
  3. Coelenterates and Ctenophores – Radial symmetry
  4. Platyhelminthes – Diploblastic organisation
Show answer
Answer: (D) Platyhelminthes – Diploblastic organisation
Explanation: Platyhelminthes are triploblastic, not diploblastic, so this pair is incorrect. Annelids and arthropods are bilaterally symmetrical, sponges lack a coelom, and coelenterates and ctenophores are radially symmetrical.

Question 2

Previous-year question
Assertion: In hemichordates, the body cavity is lined by mesoderm. [NEET (Sawaimadhopur) 2024]
Reason: In aschelminthes, the body cavity is not lined by mesoderm.
  1. Both A and R are true but R is NOT the correct explanation of A.
  2. A is true but R is false.
  3. A is false but R is true.
  4. Both A and R are true and R is the correct explanation of A.
Show answer
Answer: (A) Both A and R are true but R is NOT the correct explanation of A.
Explanation: Hemichordates are coelomates, so their body cavity is lined by mesoderm (A true). Aschelminthes are pseudocoelomates whose body cavity is not lined by mesoderm (R true). R describes a different group and does not explain A.

Question 3

Previous-year question
A coelom derived from the blastocoel is known as [AIPMT 1994]
  1. enterocoelom
  2. schizocoelom
  3. pseudocoelom
  4. haemocoelom
Show answer
Answer: (C) pseudocoelom
Explanation: A body cavity derived from the persistent embryonic blastocoel is a pseudocoelom, because it is not entirely lined by peritoneum (the thin cellular membrane derived from mesoderm). Such a cavity is found in Nemathelminthes (Aschelminthes). Schizocoelom arises by splitting of the mesoderm and enterocoelom by outpocketing of the archenteron.

Question 4

Previous-year question
Radial symmetry is often exhibited by animals having [AIPMT 1994]
  1. one opening of the alimentary canal
  2. aquatic mode of living
  3. benthos/sedentary habit
  4. ciliary mode of feeding
Show answer
Answer: (C) benthos/sedentary habit
Explanation: Radial symmetry is typically shown by animals that are sessile, bottom-dwelling (benthic) or only weakly swimming, i.e. those following a sedentary lifestyle. A radially arranged body allows such animals to interact with the environment equally from every direction.

Question 5

Previous-year question
Organisms attached to the substratum generally possess [AIPMT 1995]
  1. radial symmetry
  2. one single opening of the digestive canal
  3. asymmetrical body
  4. cilia on the surface to create a water current
Show answer
Answer: (A) radial symmetry
Explanation: Sessile organisms attached to a substratum generally possess radial symmetry, because food and danger may approach from any direction and a radially arranged body can respond equally in all directions. Corals, sea anemones and many sponges illustrate this.

Question 6

Previous-year question
Besides Annelida and Arthropoda, metamerism is also exhibited by [AIPMT 1995]
  1. Cestoda
  2. Chordata
  3. Mollusca
  4. Acanthocephala
Show answer
Answer: (B) Chordata
Explanation: Chordates also exhibit metameric segmentation, seen in the serial repetition of homologous structures such as myotomes, vertebrae and spinal nerves along the length of the animal. The proglottids of Cestoda represent pseudo-segmentation, not true metamerism.

Question 7

Previous-year question
Radial symmetry is usually associated with [AIPMT 1996]
  1. aquatic mode of life
  2. lower grade of organisation
  3. creeping mode of locomotion
  4. sedentary mode of life
Show answer
Answer: (D) sedentary mode of life
Explanation: Radial symmetry is typically associated with sessile or sedentary animals such as sponges, cnidarians and adult echinoderms, which meet their environment equally from all sides.
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Question 8

Previous-year question
The true coelom is the space lying between the alimentary canal and the body wall, enclosed by layers of [AIPMT 1996]
  1. ectoderm on both sides
  2. endoderm on one side and ectoderm on the other
  3. mesoderm on one side and ectoderm on the other
  4. mesoderm on both sides
Show answer
Answer: (D) mesoderm on both sides
Explanation: Coeloms are secondary body cavities bounded on all sides by mesodermal peritoneum, so the cavity is lined by mesoderm on both sides. The true coelom arises within the mesoderm itself, either by splitting (schizocoely) or by outpocketing of the archenteron (enterocoely).

Question 9

Previous-year question
Which of the following animals has scattered cells with the cell-tissue grade of organisation? [AIPMT 2000]
  1. Sponge
  2. Hydra
  3. Liver fluke
  4. Ascaris
Show answer
Answer: (B) Hydra
Explanation: Hydra shows the tissue level of organisation — its body is multicellular and the cells are arranged in two distinct layers of specialised cells. Sponges have only the cellular level of organisation, while the liver fluke and Ascaris have advanced to the organ-system level.

Question 10

Previous-year question
Metameric segmentation is the characteristic of [AIPMT 2006]
  1. Mollusca and Chordata
  2. Platyhelminthes and Arthropoda
  3. Echinodermata and Annelida
  4. Annelida and Arthropoda
Show answer
Answer: (D) Annelida and Arthropoda
Explanation: Metamerism is the linear repetition of parts along the body axis, each repeated segment being called a metamere or somite. It is characteristically observed in the phyla Annelida and Arthropoda. (Chordates show a form of metameric segmentation too, but the classic invertebrate pairing is Annelida and Arthropoda.)

Question 11

Previous-year question
Which one of the following groups of animals is bilaterally symmetrical and triploblastic? [AIPMT 2009]
  1. Coelenterates (cnidarians)
  2. Aschelminthes (roundworms)
  3. Ctenophores
  4. Sponges
Show answer
Answer: (B) Aschelminthes (roundworms)
Explanation: Aschelminthes are bilaterally symmetrical and triploblastic, e.g. Ascaris. Coelenterates (Obelia) are radially symmetrical and diploblastic, ctenophores (Ctenoplana) are diploblastic with biradial symmetry, and sponges (Sycon) are asymmetrical or radially symmetrical and diploblastic.

Question 12

Previous-year question
Which one of the following statements about certain given animals is correct? [AIPMT 2010]
  1. Roundworms (Aschelminthes) are pseudocoelomates
  2. Molluscs are acoelomates
  3. Insects are pseudocoelomates
  4. Flatworms (Platyhelminthes) are coelomates
Show answer
Answer: (A) Roundworms (Aschelminthes) are pseudocoelomates
Explanation: Roundworms of the phylum Aschelminthes possess a pseudocoelom, a false coelom derived from the embryonic blastocoel and not lined by mesodermal peritoneum. Flatworms are acoelomate, while molluscs and insects (Arthropoda) are true coelomate animals.

Question 13

Previous-year question
Bilaterally symmetrical and acoelomate animals are exemplified by [NEET (Sep.) 2020]
  1. Platyhelminthes
  2. Aschelminthes
  3. Annelida
  4. Ctenophora
Show answer
Answer: (A) Platyhelminthes
Explanation: Platyhelminthes are bilaterally symmetrical, triploblastic and acoelomate animals with the organ level of body organisation. Aschelminthes are bilaterally symmetrical but pseudocoelomate; Annelida are bilaterally symmetrical and truly schizocoelomate; and Ctenophora are biradially symmetrical, diploblastic and acoelomate.

Question 14

Previous-year question
A closed circulatory system occurs in [1994]
  1. cuttlefish
  2. snail
  3. all of these
  4. cockroach
Show answer
Answer: (A) cuttlefish
Explanation: Most molluscs and all arthropods have an open circulation in which blood is pumped into a haemocoel and bathes the tissues directly. The cephalopods, however, are active swimmers whose high metabolic demand is met by a closed system in which the blood remains within vessels, so the cuttlefish is exceptional among molluscs in this respect.

Question 15

Previous-year question
Just as nephridia serve their function in the earthworm, so do [1997]
  1. flame cells in the liver fluke
  2. parotid glands in the toad
  3. myotomes in the fish
  4. statocysts in the prawn
Show answer
Answer: (A) flame cells in the liver fluke
Explanation: Nephridia are the excretory and osmoregulatory organs of the earthworm, and the flame cells or solenocytes of the liver fluke perform precisely the same function in the flatworms, filtering waste and driving it along the protonephridial ducts. The parotid gland is a poison gland, myotomes are muscle blocks, and statocysts are organs of balance.

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