groups-within-the-animal-kingdom MCQs for UPSC Prelims

25 practice questions on groups-within-the-animal-kingdom from the Patterns in Life: Diversity and Classification section of the UPSC Prelims syllabus. 25 come with a written explanation. Try the sample set below - the answer stays hidden until you ask for it.

7 Easy 13 Medium 5 Hard

Sample questions

Q1
hard
Three worms are described. (I) A flattened worm bearing hooks and suckers, attached inside a host's gut. (II) A cylindrical unsegmented worm living in soil, with a mouth at one end and an anus at the other. (III) A cylindrical worm of moist soil, divided into many segments, with muscles for movement and a nerve cord. Which groups do they belong to, in that order?
  1. A Annelida, Nematoda, Platyhelminthes
  2. B Platyhelminthes, Nematoda, Annelida
  3. C Platyhelminthes, Annelida, Nematoda
  4. D Nematoda, Platyhelminthes, Annelida
Show answer and explanation

Correct answer: B - Platyhelminthes, Nematoda, Annelida

Hooks and suckers on a flattened parasitic body mark a platyhelminth, an unsegmented cylindrical worm with two gut openings is a nematode, and a segmented cylindrical worm with muscles and a nerve cord is an annelid. Any order beginning with a roundworm or a segmented worm contradicts the flattened parasitic description, and swapping the last two ignores the presence of segments.
Q2
medium
Amphioxus is a small marine animal that possesses a notochord at some stage of its life but never develops a vertebral column. How is it classified?
  1. A As a vertebrate, since a notochord is simply another name for a backbone
  2. B As an echinoderm, since it lives in the sea and has internal support
  3. C As a protochordate, a primitive chordate showing a notochord without a backbone
  4. D As an invertebrate, since it has no backbone at any stage
Show answer and explanation

Correct answer: C - As a protochordate, a primitive chordate showing a notochord without a backbone

Chordata is divided into protochordata and vertebrata, and an animal with a notochord but no vertebral column is a protochordate. Possessing a notochord already makes it a chordate rather than an invertebrate. A notochord is a flexible rod and not a backbone, and echinoderms have a calcium carbonate skeleton with no notochord at all.
Q3
hard
Assertion (A): A starfish is not classified as a chordate. Reason (R): A starfish has a hard internal skeleton made of calcium carbonate.
  1. A Both A and R are true, and R is the correct explanation of A
  2. B Both A and R are true, but R is not the correct explanation of A
  3. C A is true, but R is false
  4. D A is false, but R is true
Show answer and explanation

Correct answer: B - Both A and R are true, but R is not the correct explanation of A

(A) is true, because starfish are echinoderms and lie outside Chordata. (R) is also true, since their internal skeleton is indeed made of calcium carbonate. But an internal skeleton is not why they are excluded from Chordata; the real reason is that they never develop a notochord, so the reason does not explain the assertion.
Q4
medium
Assertion (A): In a jellyfish, the same opening is used both to take in food and to remove waste. Reason (R): Cnidarians have an organ system level of body organisation.
  1. A Both A and R are true, and R is the correct explanation of A
  2. B Both A and R are true, but R is not the correct explanation of A
  3. C A is true, but R is false
  4. D A is false, but R is true
Show answer and explanation

Correct answer: C - A is true, but R is false

(A) is true, since cnidarians such as jellyfish, corals and Hydra have a single opening serving both purposes. (R) is false, because cnidarians reach only the tissue level of organisation; organ system organisation appears later, in groups such as the roundworms and the annelids. A false reason cannot explain a true assertion.
Q5
medium
On what basis is the animal kingdom first divided into two large groups?
  1. A Whether the animal is a producer or a consumer
  2. B The presence or absence of a notochord
  3. C Whether the animal lives on land or in water
  4. D The presence or absence of a segmented body
Show answer and explanation

Correct answer: B - The presence or absence of a notochord

The first major split in Animalia is between the chordates, which have a notochord, and the non-chordates or invertebrates, which do not. Segmentation appears in more than one invertebrate group and cannot make this split. Habitat is not used as the basis, and every animal is a consumer, so nutrition separates none of them.
Q6
easy
Vertebrates are animals that possess which structure?
  1. A A vertebral column that supports the body and protects the spinal cord
  2. B An external skeleton made of chitin
  3. C Tentacles used for capturing prey
  4. D Pores through which water flows into the body
Show answer and explanation

Correct answer: A - A vertebral column that supports the body and protects the spinal cord

A vertebral column, or backbone, is what makes an animal a vertebrate, and it supports the body while protecting the spinal cord. A chitin exoskeleton belongs to arthropods. Pores for water flow describe sponges, and tentacles for capturing prey describe cnidarians.
Q7
medium
How are fins and gills suited to the surroundings in which a fish lives?
  1. A Both fins and gills let the fish breathe air directly
  2. B Both fins and gills are used only for attracting a mate
  3. C Fins drive and steer the body through water, while gills take in oxygen dissolved in the water
  4. D Fins take in oxygen from the water, while gills push the body forward
Show answer and explanation

Correct answer: C - Fins drive and steer the body through water, while gills take in oxygen dissolved in the water

Fins allow a fish to move and steer in water, and gills let it take up the oxygen dissolved there, so the two features together suit life in water. Swapping their roles reverses the biology. Neither structure exists mainly for display, and gills cannot take oxygen from air in the way lungs do.
Q8
easy
Thick fur on a polar bear is a structural feature that helps the animal in which way?
  1. A It helps the animal breathe under water
  2. B It helps the animal survive extreme cold
  3. C It helps the animal fly
  4. D It helps the animal make its own food
Show answer and explanation

Correct answer: B - It helps the animal survive extreme cold

A thick coat of fur traps warmth and lets a polar bear withstand extreme cold, in the same way that fat storage helps a camel cope with its own harsh surroundings. Flight depends on feathers and light bones, breathing under water depends on gills, and no animal makes its own food.

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