Animal Kingdom — NEET Zoology MCQs with answers

Animal Kingdom is a Class 11 Zoology chapter in the NEET (UG) syllabus. NEET720 has 2,021 reviewed practice questions on it, each with a quick answer and a step-by-step explanation. The 8 questions below are free and fixed, so you can bookmark this page; the full chapter, plus mistake tracking and spaced revision, is in the app.

Topics covered

Protochordata and Cyclostomata · Basis of Classification · Porifera, Cnidaria and Ctenophora · Platyhelminthes, Aschelminthes and Annelida · Arthropoda, Mollusca, Echinodermata and Hemichordata · Protochordates and Cyclostomata · Pisces · Amphibia and Reptilia · Aves and Mammalia · Phylum Coelenterata · Phylum Cnidaria (Coelenterata) · Subphylum Vertebrata: Pisces · Subphylum Vertebrata: Amphibia · Subphylum Vertebrata: Reptilia · Subphylum Vertebrata: Aves · Subphylum Vertebrata: Mammalia · Subphylum Vertebrata: Chordata general characters · Subphylum Vertebrata: Protochordata · Subphylum Vertebrata: Amphibia versus Pisces circulation · Levels of organisation · Symmetry · Cyclostomata · Osteichthyes · Structural comparison · Phylum Coelenterata vs Ctenophora · Subphylum classification of Chordata · Chordata general characteristics · Class Pisces (Osteichthyes) · Body plan and organisation levels · Phylum Cnidaria · Phylum Platyhelminthes · Class Pisces · General classification · Classification Basis · Animal Kingdom Classification · Phylum identification from observations · Class identification from observations · Interpreting observations · Chordate subgroup identification · Interpreting anomalies

8 free Animal Kingdom practice questions with answers

Choose an answer in your head before opening it. Each explanation says why the correct option is right and, where relevant, why the tempting wrong option is wrong.

1. Question 1 · easy · Arthropoda, Mollusca, Echinodermata and Hemichordata

   Phylum Arthropoda is the largest phylum of the Animal Kingdom. What fraction of all named animal species does it approximately represent?

   • A.About one-third
   • B.About one-half
   • C.More than two-thirds
   • D.Less than one-tenth
   Show answer and explanation

   Answer: C. More than two-thirds

   NCERT states arthropods comprise more than two-thirds of all named species on Earth, making Arthropoda the most successful animal phylum.

   Arthropoda includes insects, crustaceans, arachnids, and myriapods, and together these groups account for more than two-thirds (about 70%) of all named animal species, primarily due to the enormous diversity of Insecta. This makes Arthropoda by far the largest and most successful phylum in the Animal Kingdom, both in species number and ecological range. Options A, B, and D underestimate this dominance.

   Common mistake: Students often underestimate arthropod diversity relative to vertebrates.

   Key point: Arthropoda = largest phylum, more than two-thirds of all named animal species.

2. Question 2 · medium · Arthropoda, Mollusca, Echinodermata and Hemichordata

   The name 'Arthropoda' directly refers to which defining structural feature of this phylum?

   • A.Segmented body divided into head, thorax, and abdomen
   • B.Chitinous exoskeleton covering the body
   • C.Jointed appendages (legs, antennae, mouthparts)
   • D.Open circulatory system with haemolymph
   Show answer and explanation

   Answer: C. Jointed appendages (legs, antennae, mouthparts)

   'Arthropoda' literally means 'jointed legs' (Greek: arthron = joint, podos = foot), referring to the jointed appendages found throughout the phylum.

   The term Arthropoda is derived from Greek 'arthron' (joint) and 'podos' (foot/leg), so the name itself specifically denotes jointed appendages — legs, antennae, and mouthparts that move at articulated joints. While exoskeleton, body segmentation, and open circulation are all true arthropod characters, they are not what the phylum's name refers to. Jointed appendages are considered the single most defining feature that gives the phylum its name.

   Common mistake: Confusing the name's meaning with other true but non-namesake characters like exoskeleton.

   Key point: Arthropoda = 'jointed legs/feet' — jointed appendages are the namesake character.

3. Question 3 · medium · Arthropoda, Mollusca, Echinodermata and Hemichordata

   Which of the following correctly pairs an arthropod respiratory organ with the habitat in which it is typically found?

   • A.Gills — terrestrial insects
   • B.Tracheal tubes — aquatic crustaceans
   • C.Book lungs — terrestrial arachnids
   • D.Book gills — terrestrial insects
   Show answer and explanation

   Answer: C. Book lungs — terrestrial arachnids

   Respiratory organs in arthropods vary by habitat: aquatic forms use gills, terrestrial forms use tracheal tubes (insects) or book lungs (arachnids like spiders and scorpions).

   Arthropod respiratory structures are adapted to habitat: aquatic crustaceans (prawns, crabs) respire through gills; terrestrial insects respire through a network of tracheal tubes opening via spiracles; terrestrial arachnids (spiders, scorpions) respire through book lungs, which are stacked leaf-like lamellae enclosed in a chamber. Book gills are a distinct structure found in aquatic chelicerates such as horseshoe crabs (Limulus), not insects. This question tests correct matching of respiratory structure to habitat and taxon, a frequently tested NEET point.

   Common mistake: Confusing book lungs (arachnids) with book gills (aquatic chelicerates like Limulus).

   Key point: Aquatic arthropods → gills; terrestrial insects → tracheae; terrestrial arachnids → book lungs.

4. Question 4 · easy · Arthropoda, Mollusca, Echinodermata and Hemichordata

   Which of the following is the diagnostic feature used to distinguish class Crustacea from other arthropod classes?

   • A.Presence of two pairs of antennae
   • B.Presence of one pair of antennae
   • C.Complete absence of antennae
   • D.Presence of three pairs of antennae
   Show answer and explanation

   Answer: A. Presence of two pairs of antennae

   Class Crustacea is distinguished by two pairs of antennae, unlike Insecta (one pair) and Arachnida (none).

   Crustaceans, which are mostly aquatic arthropods such as prawns, crabs, lobsters, Daphnia, and barnacles like Lepas, are characterized by having two pairs of antennae. This distinguishes them from Insecta, which has only one pair of antennae, and Arachnida, which lacks antennae altogether. This antennae-count comparison across classes is one of the most frequently tested classification points in NEET Animal Kingdom.

   Common mistake: Mixing up antennae counts between Crustacea and Insecta.

   Key point: Crustacea = two pairs of antennae (Insecta = one pair; Arachnida = none).

5. Question 5 · easy · Arthropoda, Mollusca, Echinodermata and Hemichordata

   Which combination of features correctly characterizes class Insecta?

   • A.Two pairs of antennae, four pairs of legs
   • B.One pair of antennae, three pairs of legs
   • C.No antennae, three pairs of legs
   • D.One pair of antennae, four pairs of legs
   Show answer and explanation

   Answer: B. One pair of antennae, three pairs of legs

   Insecta, the largest group of arthropods, is characterized by one pair of antennae and three pairs of legs, and members are generally winged.

   Class Insecta is the largest group within Arthropoda and includes examples like Periplaneta (cockroach), Bombyx (silkworm), Apis (honey bee), Anopheles (mosquito), and butterflies. Insects possess one pair of antennae and three pairs of jointed legs, with the body divided into head, thorax, and abdomen; most are winged. This is distinct from Crustacea (two pairs of antennae) and Arachnida (no antennae, four pairs of legs).

   Common mistake: Confusing insect leg/antennae counts with those of Arachnida or Crustacea.

   Key point: Insecta: one pair antennae, three pairs legs, generally winged.

6. Question 6 · medium · Arthropoda, Mollusca, Echinodermata and Hemichordata

   Which set of features correctly describes class Arachnida?

   • A.Mostly aquatic; two pairs of antennae; five pairs of legs
   • B.Mostly terrestrial; two pairs of antennae; four pairs of legs
   • C.Mostly terrestrial; one pair of antennae; three pairs of legs
   • D.Mostly terrestrial; no antennae; four pairs of legs
   Show answer and explanation

   Answer: D. Mostly terrestrial; no antennae; four pairs of legs

   Arachnida (spiders, scorpions, mites, ticks) are mostly terrestrial, lack antennae, respire via book lungs, and have four pairs of legs.

   Class Arachnida includes spiders, scorpions, mites, and ticks. They are mostly terrestrial animals that respire through book lungs, completely lack antennae, and possess four pairs of walking legs (unlike insects with three pairs). This distinguishes them clearly from Insecta (one pair antennae, three pairs legs) and Crustacea (two pairs antennae, mostly aquatic). Precise recall of these class-defining numbers is a classic NEET classification question.

   Common mistake: Assuming arachnids have antennae like insects or crustaceans.

   Key point: Arachnida: no antennae, four pairs of legs, book lungs, mostly terrestrial.

7. Question 7 · medium · Arthropoda, Mollusca, Echinodermata and Hemichordata

   The circulatory system of arthropods is best described as which of the following?

   • A.Closed, with blood confined to vessels throughout
   • B.Open, with haemolymph bathing tissues directly in a haemocoel
   • C.Absent, as arthropods rely solely on diffusion
   • D.Closed, but restricted only to the respiratory organs
   Show answer and explanation

   Answer: B. Open, with haemolymph bathing tissues directly in a haemocoel

   Arthropods have an open circulatory system in which haemolymph (blood) is pumped by a dorsal heart into a body cavity called the haemocoel, directly bathing tissues.

   In arthropods, the circulatory system is of the open type: the heart pumps haemolymph into large sinuses that together form the haemocoel, where the fluid directly bathes internal organs and tissues before returning to the heart through openings called ostia. This is unlike the closed circulatory system of annelids or vertebrates, where blood remains confined within vessels. Because respiration is often handled independently by tracheae (in insects) or gills/book lungs, the open circulatory system in arthropods is adequate despite not being as efficient in oxygen transport as a closed system.

   Common mistake: Assuming all complex organ-system-level animals must have closed circulation.

   Key point: Arthropod circulation = open type, haemolymph in haemocoel, not confined to vessels.

8. Question 8 · medium · Arthropoda, Mollusca, Echinodermata and Hemichordata

   Statocysts, when present in arthropods, primarily function to detect which of the following?

   • A.Light intensity and colour
   • B.Chemical stimuli such as taste and smell
   • C.Body orientation and balance relative to gravity
   • D.Vibrations transmitted through air
   Show answer and explanation

   Answer: C. Body orientation and balance relative to gravity

   Statocysts are balance organs that help arthropods (e.g., crustaceans) sense their orientation and maintain equilibrium relative to gravity.

   Statocysts are small fluid-filled sensory structures containing a granule (statolith) that shifts with gravity, found in some crustaceans. As the animal changes orientation, the statolith presses on sensory hairs lining the statocyst, allowing the animal to detect its position relative to gravity and maintain balance. This is distinct from compound eyes (which detect light), antennae (which detect chemical and tactile stimuli), and other specialized sensory structures. NCERT lists statocysts as one of the sensory organs found in arthropods alongside antennae and eyes.

   Common mistake: Confusing statocysts with visual or auditory sensory structures.

   Key point: Statocysts = balance/gravity-orientation organs in arthropods.

Questions about Animal Kingdom for NEET

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