40 free MCQs on Animal Kingdom with worked answers and explanations. Phylum-level classification of the animal kingdom from Porifera to Chordata, based on body symmetry, coelom, and segmentation. One of the most example-heavy chapters for NEET.
Below are 40 practice questions on Animal Kingdom, sorted Easy → Hard. Tap “Show answer & explanation” under any question to check yourself. Want the full theory first? Read the Animal Kingdom notes.
Moving across the animal phyla, body organisation becomes progressively more complex: from no symmetry and cellular organisation (Porifera) through radial/diploblastic (Cnidaria), bilateral/acoelomate (Platyhelminthes), pseudocoelomate (Nematoda), to a true coelom with full organ systems (Annelida and beyond).
Easy — 15 questions
Q1.
Which phylum is known as the sponges?
A Cnidaria
B Porifera
C Ctenophora
D Platyhelminthes
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Answer: B. Porifera
Why: Phylum Porifera includes sponges, which have numerous pores (ostia) and a cellular level of organization.
Q2.
Hydra belongs to which phylum?
A Porifera
B Cnidaria
C Ctenophora
D Annelida
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Answer: B. Cnidaria
Why: Hydra is a freshwater cnidarian (Coelenterata) that shows radial symmetry and a polyp body form.
Q3.
Tapeworm (Taenia) belongs to which phylum?
A Nematoda
B Platyhelminthes
C Annelida
D Arthropoda
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Answer: B. Platyhelminthes
Why: Taenia (tapeworm) is a flatworm belonging to phylum Platyhelminthes; it is an endoparasite found in the intestine.
Q4.
Ascaris (roundworm) is a member of phylum
A Platyhelminthes
B Nematoda
C Annelida
D Mollusca
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Answer: B. Nematoda
Why: Ascaris is a parasitic roundworm of phylum Nematoda, characterized by a pseudocoelom and a circular cross section.
Q5.
Earthworm (Pheretima) belongs to which phylum?
A Nematoda
B Annelida
C Arthropoda
D Mollusca
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Answer: B. Annelida
Why: Earthworm belongs to phylum Annelida, characterized by true segmentation (metamerism) and a true coelom.
Q6.
Which is the largest phylum in the animal kingdom?
A Mollusca
B Annelida
C Arthropoda
D Chordata
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Answer: C. Arthropoda
Why: Arthropoda is the largest phylum, comprising more than two-thirds of all named animal species, including insects, crustaceans, and arachnids.
Q7.
Octopus and Pila belong to which phylum?
A Echinodermata
B Mollusca
C Arthropoda
D Hemichordata
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Answer: B. Mollusca
Why: Octopus and Pila are both members of phylum Mollusca, characterized by a soft body with a head, visceral hump, and muscular foot.
Q8.
Starfish (Asterias) belongs to which phylum?
A Mollusca
B Echinodermata
C Hemichordata
D Chordata
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Answer: B. Echinodermata
Why: Starfish belongs to phylum Echinodermata, marine animals with a calcareous endoskeleton and a unique water vascular system.
Q9.
Which structure is characteristic of all members of phylum Chordata?
A Radula
B Notochord
C Water vascular system
D Cnidoblasts
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Answer: B. Notochord
Why: The presence of a notochord at some stage of life is a defining feature of phylum Chordata, along with a dorsal hollow nerve cord and paired gill slits.
Q10.
Frogs and toads belong to which vertebrate class?
A Reptilia
B Amphibia
C Pisces
D Mammalia
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Answer: B. Amphibia
Why: Frogs (Rana) and toads (Bufo) belong to class Amphibia, which can live in both freshwater and on land.
Q11.
Which class of vertebrates is characterized by the presence of feathers?
A Reptilia
B Aves
C Mammalia
D Amphibia
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Answer: B. Aves
Why: Class Aves (birds) is uniquely characterized by the presence of feathers and forelimbs modified into wings.
Q12.
Which of the following is an egg-laying mammal?
A Kangaroo, a marsupial that gives birth to underdeveloped young
B Platypus (Ornithorhynchus)
C Camel, a placental mammal adapted to arid desert environments
D Monkey, a placental primate with prolonged gestation
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Answer: B. Platypus (Ornithorhynchus)
Why: Ornithorhynchus (platypus) and Tachyglossus (echidna) are egg-laying mammals (monotremes), an exception to the rule that mammals are viviparous.
Q13.
Which phylum includes comb jellies such as Pleurobrachia?
A Cnidaria
B Ctenophora
C Porifera
D Echinodermata
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Answer: B. Ctenophora
Why: Pleurobrachia is a comb jelly belonging to phylum Ctenophora, exclusively marine animals that move using comb plates and show bioluminescence.
Q14.
Cockroach (Periplaneta) belongs to which phylum and class?
A Mollusca, Gastropoda
B Arthropoda, Insecta
C Annelida, Polychaeta
D Chordata, Reptilia
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Answer: B. Arthropoda, Insecta
Why: Cockroach belongs to phylum Arthropoda, class Insecta, characterized by jointed appendages and a chitinous exoskeleton.
Q15.
What is the main excretory organ found in earthworms?
A Flame cells
B Nephridia
C Malpighian tubules
D Green glands
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Answer: B. Nephridia
Why: Earthworms (Annelida) have nephridia as excretory organs. Flame cells are found in flatworms, and Malpighian tubules in insects.
Medium — 14 questions
Q16.
Which feature distinguishes pseudocoelomates from true coelomates?
A Pseudocoelomates have no body cavity
B Pseudocoelomates have a body cavity that is not lined by mesoderm
C Pseudocoelomates have a body cavity lined largely by mesoderm
D There is no difference, the terms are interchangeable
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Answer: B. Pseudocoelomates have a body cavity that is not lined by mesoderm
Why: In pseudocoelomates such as Nematoda, the body cavity is not lined by mesoderm on both sides; in true coelomates, the body cavity is completely lined by mesoderm.
Q17.
Animals showing diploblastic organization, like Hydra, have body walls made of how many germ layers?
A One layer with no distinction
B Two layers: ectoderm and endoderm
C Three layers: ectoderm, mesoderm, and endoderm
D Four distinct layers
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Answer: B. Two layers: ectoderm and endoderm
Why: Diploblastic animals (Cnidaria, Ctenophora) have two embryonic germ layers, ectoderm and endoderm, with an undifferentiated mesoglea in between.
Q18.
Which of the following correctly matches the phylum with its type of symmetry?
A Porifera, exhibiting bilateral body symmetry overall
B Echinodermata adults, radial symmetry
C Annelida, exhibiting radial body symmetry overall
D Platyhelminthes, lacking any defined body symmetry
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Answer: B. Echinodermata adults, radial symmetry
Why: Echinodermata show radial symmetry as adults but bilateral symmetry as larvae. Porifera is generally asymmetrical, and Annelida and Platyhelminthes show bilateral symmetry.
Q19.
What is the function of cnidoblasts (cnidocytes) found in Cnidaria?
A Digestion of food in the gastrovascular cavity
B Excretion of nitrogenous wastes
C Defense and capturing of prey via stinging cells
D Locomotion by water expulsion
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Answer: C. Defense and capturing of prey via stinging cells
Why: Cnidoblasts (cnidocytes) are specialized stinging cells present on the tentacles of cnidarians, used for anchorage, defense, and capturing prey.
Q20.
Which type of circulatory system is found in Arthropoda?
A Closed circulatory system
B Open circulatory system
C No circulatory system
D Double circulation only
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Answer: B. Open circulatory system
Why: Arthropods have an open circulatory system in which blood (hemolymph) flows freely in body spaces (hemocoel) rather than being confined to vessels.
Q21.
The water vascular system, used for locomotion and respiration, is a unique feature of which phylum?
A Mollusca
B Echinodermata
C Hemichordata
D Annelida
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Answer: B. Echinodermata
Why: The water vascular system, ending in tube feet, is a unique feature of Echinodermata, used for locomotion, capturing food, and respiration.
Q22.
Which structure in molluscs is used as a rasping organ for feeding?
A Radula
B Mantle
C Spicule
D Madreporite
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Answer: A. Radula
Why: The radula is a file-like rasping organ found in the mouth of most molluscs, used to scrape food. The mantle covers the visceral hump.
Q23.
Which subphylum or group of Chordata retains the notochord throughout life, extending from head to tail?
A Urochordata
B Cephalochordata
C Vertebrata only
D Hemichordata
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Answer: B. Cephalochordata
Why: In Cephalochordata (e.g., Branchiostoma), the notochord extends from head to tail and persists throughout life. In Urochordata, it is present only in the larval tail.
Q24.
Which of the following animals lacks separate sexes (is hermaphroditic)?
A Ascaris, a parasitic roundworm species
B Earthworm (Pheretima)
C Periplaneta, the common cockroach
D Asterias, a marine starfish species
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Answer: B. Earthworm (Pheretima)
Why: Earthworms are hermaphrodites, possessing both male and female reproductive organs in the same individual, though cross-fertilization is the norm.
Q25.
Which class of fishes lacks an operculum (gill cover) over the gill slits?
A Osteichthyes
B Chondrichthyes
C Amphibia
D Cyclostomata
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Answer: B. Chondrichthyes
Why: Chondrichthyes (cartilaginous fishes such as sharks and rays) have separate gill slits without an operculum, unlike Osteichthyes (bony fishes), which have gills covered by an operculum.
Q26.
Which class of vertebrates typically has a three-chambered heart, with crocodiles being a notable exception?
A Amphibia
B Reptilia
C Aves
D Mammalia
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Answer: B. Reptilia
Why: Most reptiles have a three-chambered heart, but crocodiles are an exception, possessing a four-chambered heart.
Q27.
Which phylum was previously considered a subphylum of Chordata but is now treated as a separate phylum?
A Cephalochordata
B Urochordata
C Hemichordata
D Echinodermata
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Answer: C. Hemichordata
Why: Hemichordata was earlier considered a subphylum of Chordata, but is now classified as a separate phylum since the presence of a true notochord in these animals is doubtful.
Q28.
Which of these features is shared by both Annelida and Arthropoda?
A Open circulatory system in both
B Metameric segmentation of the body
C Absence of a coelom
D Exoskeleton made of chitin in both
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Answer: B. Metameric segmentation of the body
Why: Both Annelida and Arthropoda show metameric segmentation (repetition of body segments), though Annelida has a closed circulatory system while Arthropoda has an open one, and only Arthropoda has a chitinous exoskeleton.
Q29.
Mammary glands, hair on skin, and a four-chambered heart are characteristic features of which class?
A Aves
B Reptilia
C Mammalia
D Amphibia
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Answer: C. Mammalia
Why: Mammalia is characterized by mammary glands for nourishing young, hair on the skin, sweat and oil glands, and a four-chambered heart.
Hard — 11 questions
Q30.
An animal has a triploblastic body, bilateral symmetry, a pseudocoelom, and a complete digestive system but lacks circulatory and respiratory systems. Which phylum does it most likely belong to?
A Platyhelminthes
B Nematoda
C Annelida
D Mollusca
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Answer: B. Nematoda
Why: Nematodes are triploblastic, bilaterally symmetrical, pseudocoelomate animals with a complete alimentary canal but no circulatory or respiratory system, exemplified by Ascaris and Wuchereria.
Q31.
Which set correctly distinguishes Cephalochordata from Urochordata?
A Cephalochordata retains the notochord only in the larval tail before resorption at metamorphosis; Urochordata retains it for life
B Cephalochordata retains the notochord from head to tail throughout life; Urochordata retains it only in the larval tail
C Both groups retain a fully ossified vertebral column replacing the notochord in adults
D Neither group develops a notochord at any embryonic or adult stage
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Answer: B. Cephalochordata retains the notochord from head to tail throughout life; Urochordata retains it only in the larval tail
Why: In Cephalochordata (Amphioxus/Branchiostoma), the notochord persists from head to tail throughout life. In Urochordata (Ascidia), the notochord is present only in the larval tail and is lost in the adult.
Q32.
Which combination of features would correctly identify an organism as belonging to class Chondrichthyes rather than Osteichthyes?
A Bony endoskeleton, gills covered by operculum, terminal mouth according to most researchers
B Cartilaginous endoskeleton, ventrally placed mouth, gill slits without operculum
C Cartilaginous endoskeleton, four-chambered heart, feathers in the majority of cases studied
D Bony endoskeleton, placoid scales, dorsal mouth as widely reported in standard practice
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Answer: B. Cartilaginous endoskeleton, ventrally placed mouth, gill slits without operculum
Why: Chondrichthyes (e.g., Scoliodon, sharks) have a cartilaginous endoskeleton, ventrally placed mouth, and separate gill slits without an operculum, plus placoid scales. Osteichthyes have a bony skeleton and an operculum covering the gills.
Q33.
Why is Balanoglossus no longer classified within phylum Chordata despite historically being grouped with it?
A It lacks bilateral symmetry, instead showing radial symmetry typical of cnidarians under most conditions encountered
B The presence of a true notochord in Balanoglossus is doubtful, so Hemichordata is now a separate phylum
C It possesses a closed circulatory system, unlike the open system found in true chordates as commonly observed in practice
D It develops without a coelomic body cavity during embryogenesis in many documented cases according to conventional understanding
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Answer: B. The presence of a true notochord in Balanoglossus is doubtful, so Hemichordata is now a separate phylum
Why: Balanoglossus (Hemichordata) was earlier placed under Chordata, but since the structure resembling a notochord is not considered a true notochord, Hemichordata is now classified as a distinct phylum separate from Chordata.
Q34.
A marine animal shows radial symmetry as an adult, bilateral symmetry as a larva, an endoskeleton of calcareous ossicles, and no distinct excretory system. To which phylum does it belong?
A Cnidaria
B Mollusca
C Echinodermata
D Hemichordata
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Answer: C. Echinodermata
Why: These are classic identifying features of Echinodermata (e.g., Asterias, starfish): radial symmetry in adults but bilateral in larvae, calcareous endoskeleton, water vascular system, and no specialized excretory organs.
Q35.
Which of the following is true regarding metagenesis as observed in Obelia?
A It refers to alternation between asexual polyp and sexual medusa forms within the life cycle
B It refers to the formation of a water vascular system used for locomotion in echinoderms
C It is a type of asexual budding and fragmentation seen exclusively in sponges
D It describes the alternation between haploid gametophyte and diploid sporophyte plant generations
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Answer: A. It refers to alternation between asexual polyp and sexual medusa forms within the life cycle
Why: Metagenesis in cnidarians like Obelia refers to the alternation between the asexual, sessile polyp form and the sexual, free-swimming medusa form within a single life cycle.
Q36.
Which statement correctly differentiates the levels of organization across early phyla?
A Porifera shows organ-system level with coordinated organ function, Cnidaria shows mainly cellular level
B Porifera shows cellular level, Cnidaria shows tissue level, Platyhelminthes shows organ level
C All three phyla independently evolved a largely coordinated organ-system level of organization
D Cnidaria shows organ-system level of organization that exceeds that of Platyhelminthes
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Answer: B. Porifera shows cellular level, Cnidaria shows tissue level, Platyhelminthes shows organ level
Why: Levels of organization increase in complexity: Porifera has cellular level organization, Cnidaria has tissue level, and Platyhelminthes (and other higher phyla) have organ level, progressing to organ-system level in Annelida onward.
Q37.
Which feature is unique to phylum Hemichordata that helps separate it structurally from true Chordata?
A Presence of a dorsal hollow nerve cord identical to vertebrates in routine practice
B A body divided into proboscis, collar, and trunk, with a doubtful notochord
C Possession of a vertebral column overall in most cases under typical conditions
D Presence of paired appendages like fins according to standard textbooks
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Answer: B. A body divided into proboscis, collar, and trunk, with a doubtful notochord
Why: Hemichordates like Balanoglossus have a body divided into proboscis, collar, and trunk regions, and although they show some chordate-like features, the presence of a true notochord is doubtful, distinguishing them from true Chordata.
Q38.
Which of the following correctly lists an order of increasing structural complexity in body cavity organization?
A Coelomate, pseudocoelomate, acoelomate
B Acoelomate, pseudocoelomate, coelomate
C Pseudocoelomate, coelomate, acoelomate
D Coelomate, acoelomate, pseudocoelomate
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Answer: B. Acoelomate, pseudocoelomate, coelomate
Why: Acoelomates (e.g., Platyhelminthes) have no body cavity, pseudocoelomates (e.g., Nematoda) have a body cavity not fully lined by mesoderm, and coelomates (e.g., Annelida, Arthropoda, Chordata) have a true coelom completely lined by mesoderm.
Q39.
Which feature distinguishes the class Cyclostomata from Chondrichthyes?
A Cyclostomata have jaws, Chondrichthyes are jawless in general practice as commonly described
B Cyclostomata are jawless and ectoparasitic, Chondrichthyes have jaws and are mostly predaceous
C Cyclostomata have a bony endoskeleton, Chondrichthyes have a cartilaginous one in most textbook accounts
D Cyclostomata live mainly in deserts, Chondrichthyes live mainly in rivers during normal conditions
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Answer: B. Cyclostomata are jawless and ectoparasitic, Chondrichthyes have jaws and are mostly predaceous
Why: Cyclostomata (e.g., Petromyzon, Myxine) are jawless vertebrates, often ectoparasitic on other fishes, with a cartilaginous cranium and vertebral column. Chondrichthyes (sharks, rays) have jaws and are mostly predaceous marine fishes.
Q40.
Why are sea cucumbers (Holothuria) and sea urchins (Echinus) both grouped in phylum Echinodermata despite differing body shapes?
A Both share an open circulatory system and jointed legs adapted for benthic crawling as generally observed
B Both have an endoskeleton of calcareous ossicles and a water vascular system with tube feet
C Both reproduce mainly by asexual budding without any sexual phase in typical laboratory settings
D Both lack any skeletal structure and rely on a soft protective mantle under usual circumstances
Show answer & explanation
Answer: B. Both have an endoskeleton of calcareous ossicles and a water vascular system with tube feet
Why: Despite differing external shapes, all echinoderms, including Holothuria (sea cucumber) and Echinus (sea urchin), share a calcareous endoskeleton made of ossicles and a unique water vascular system with tube feet used in locomotion and feeding.