Q.Which group of chordates possess sucking and circular mouth without jaws?
🔒You're viewing a preview — the full solution, concept, methods & PYQ mapping are locked.
🔒 Start your 14-day free trial to unlock the full solution →Concept understanding — Animal Classification
Imagine walking into a vast library with more than a million books and no shelves, no catalogue, and no order at all. Finding anything, or even understanding what the collection contains, would be hopeless. The animal kingdom presents the same challenge: biologists have already described more than a million animal species. On that scale, a systematic way of grouping animals is not a mere convenience but a necessity.
Animal classification is the orderly grouping of animals so we can make sense of their enormous variety. It lets us do three things: make sense of the sheer diversity, study a few representative types instead of every single species, and give each newly discovered animal a definite, systematic position alongside its relatives. Crucially, the grouping is not arbitrary. Although animals differ enormously in outward shape and form, they share certain deep, fundamental features, and classification is built on these shared features rather than on superficial appearances.
The fundamental characters used as the basis of classification are:
- The level of organisation of the cells (cellular, tissue, organ, or organ-system).
- The body symmetry — whether, and in how many planes, the body divides into matching halves (asymmetry, radial, or bilateral).
- The number of germ layers in the embryo (diploblastic or triploblastic).
- The nature of the coelom, or body cavity — absent, false, or a true mesoderm-lined cavity (acoelomate, pseudocoelomate, or coelomate).
- The presence of segmentation of the body.
- The presence or absence of a notochord (chordate or non-chordate).
The patterns of the digestive, circulatory, and reproductive systems are compared as well. …
Class Cyclostomata possesses a sucking, circular mouth without jaws.
- Cyclostomes are the most primitive living vertebrates, and their mouth is circular and adapted for sucking, entirely lacking jaws.
- This jawless condition places them in the division Agnatha, separate from all jawed vertebrates (Gnathostomata). …
Class Cyclostomata, the most primitive living vertebrates, is uniquely defined by a jawless, circular, sucking mouth, placing it in the division Agnatha.
Among chordates, the presence or absence of jaws marks a major evolutionary divide, splitting the vertebrates into the jawless Agnatha and the jawed Gnathostomata.
- Cyclostomes have an elongated body and a mouth that is circular and adapted for sucking, with no jaws at all — this jawless condition is exactly why they are placed in the division Agnatha.
- They live as ectoparasites, attaching to the outside of certain fishes using this sucking mouth.
- Respiration occurs through 6 to 15 pairs of gill slits, the skeleton (cranium and vertebral column) is entirely cartilaginous, and the circulatory system is closed. …
Method: Binary-split elimination (jawed vs jawless)
Rather than recalling Cyclostomata directly, use the single biggest split within the chordates — jawed versus jawless — as a first filter, and only then look inside the jawless branch for the specific mouth type described.
Step 1 — apply the first, biggest split. All chordates with a vertebral column divide into two groups: Gnathostomata (jaw-bearing) and Agnatha (jawless). A "sucking and circular mouth without jaws" is, by definition, a jawless-branch feature, so the entire Gnathostomata branch — which includes Pisces, Amphibia, Reptilia, Aves and Mammalia — can be set aside immediately without checking any of them individually.
Step 2 — look inside the remaining (Agnatha) branch. Among living vertebrates, Agnatha is represented by a single class: Cyclostomata. This class is described as the most primitive living vertebrates, with an elongated body and a mouth that is specifically circular and adapted for sucking, entirely lacking jaws — exactly matching the description in the question. …
- CBSE 2026Set ANNUAL1 markMCQQ.Match the following: List I -(a) Exocoetus,(b) Pterophyllum,(c) Betta,(d) Labeo; List II -(i) Rohu,(ii) Fighting fish,(iii) flying fish,(iv) Angel fish(a) a) (a)-(i), (b)-(ii), (c)-(iii), (d)-(iv)(b) b) (a)-(iv), (b)-(iii), (c)-(ii), (d)-(i)(c) c) (a)-(iii), (b)-(iv), (c)-(ii), (d)-(i)(d) d) (a)-(iii), (b)-(iii), (c)-(ii), (d)-(i)
›Reveal solutionSolution
[!TLDR]
c) (a)-(iii), (b)-(iv), (c)-(ii), (d)-(i)
Why
Exocoetus = flying fish, Pterophyllum = Angel fish, Betta = Fighting fish, Labeo …
- CBSE 2025Set ANNUAL1 markMCQQ.Select the incorrect statements.(a) In ctenophores, locomotion is mediated by comb plates.(b) In Prawn excretion of waste materials occurs through malpighian tubules.(c) In Fasciola, flame cells take part in excretion.(d) Earthworms are hermaphrodites and yet cross fertilization takes place among them.
›Reveal solutionSolution
Statement (b) is incorrect because prawns excrete through green (antennal) glands, not malpighian tubules — malpighian tubules are the excretory organs of insects, a different class of arthropods.
Checking each option:
- (a) is a correct statement: ctenophores (comb jellies) move using rows of ciliated comb plates on their body surface — this is true (locomotion by comb plates/cilia).
- (b) is the incorrect statement: prawns are crustaceans, and crustacean excretion occurs through green glands (antennal glands) located at the base of the antennae, not malpighian tubules. Malpighian tubules are specific to insects (a different arthropod class) for excreting nitrogenous waste as uric acid.
- (c) is a correct statement: in Fasciola (liver fluke, a flatworm) and other platyhelminthes, flame cells (protonephridia) perform osmoregulation/excretion. …
- CBSE 2024Set ANNUAL1 markMCQQ.Match the following and choose the correct option. Column A: 1) Porifera 2) Annelida 3) Arthropoda 4) Mollusca Column B: A) Metameric segmentation B) Body covered with calcareous shell and mantle C) Jointed appendages with claws D) Body perforated by pores called ostia(a) 1(D), 2(A), 3(C), 4(B)(b) 1(B), 2(D), 3(A), 4(C)(c) 1(D), 2(C), 3(A), 4(B)(d) 1(B), 2(C), 3(D), 4(A)
›Reveal solutionSolution
Each phylum's defining feature: Porifera = pores (ostia), Annelida = segmentation, Arthropoda = jointed appendages, Mollusca = shell + mantle — giving the match 1D, 2A, 3C, 4B.
Matching each animal phylum to its hallmark feature:
- Porifera (sponges) — the body is perforated by numerous minute pores called ostia, through which water enters the spongocoel; hence D) Body perforated by pores called ostia.
- Annelida (segmented worms) — the body shows true metameric segmentation (repetition of similar segments/metameres along the body length); hence A) Metameric segmentation. …
- CBSE 2024Set ANNUAL1 markMCQQ.Cellular level of organisation is seen in(a)(a) Porifera(b)(b) Coelenterata(c)(c) Annelida(d)(d) Mollusca
›Reveal solutionSolution
[!TLDR]
(a) Porifera
Why
In Porifera (sponges), cells are loosely arranged around a water canal system and do not form true tissues, representing the cellular level of organisation …
- CBSE 2023Set ANNUAL1 markMCQQ.Match the column. Item: Flame cell(a) Stigma(b) Cell division(c) Platyhelminthes(d) Cochlea(e) Earthworm(f) Lactation(g) Glycolysis
›Reveal solutionSolution
Flame cells are the excretory cells characteristic of flatworms (phylum Platyhelminthes), so Flame cell matches with Platyhelminthes.
Flame cells (also called protonephridia or solenocytes) are the primitive excretory structures found in organisms like Planaria (a free-living flatworm). Each flame cell has a tuft of cilia inside a hollow bulb that beats constantly, resembling a flickering flame, and creates a current that draws in fluid waste and drives it out throu …
- CBSE 2023Set ANNUAL1 markMCQQ.Match the column. Item: Typhlosole(a) Stigma(b) Cell division(c) Platyhelminthes(d) Cochlea(e) Earthworm(f) Lactation(g) Glycolysis
›Reveal solutionSolution
Typhlosole is a dorsal, longitudinal fold projecting into the intestine that increases the surface area for digestion and absorption, a characteristic feature of the earthworm's alimentary canal.
In the earthworm (Pheretima/Lumbricus), the intestine (from about the 26th/27th segment onward) develops a prominent, ridge-like infolding of its dorsal wall projecting into the intestinal lumen — this is the typhlosole. By increasing the internal absorptive surface area without having to increase overall body/int …
- CBSE 2019Set ANNUAL1 markQ.Give the scientific name of cockroach.
›Reveal solutionSolution
The common cockroach studied in NCERT Biology is scientifically named Periplaneta americana, following the binomial nomenclature system (Genus + species).
In binomial nomenclature, every organism is given a two-part Latinised name: the first part is the Genus (capitalised), and the second is the species (lowercase), both italicised or underlined when handwritten. The cockroach commonly used as a representative …
- CBSE 2018Set ZOOLOGY1 markQ.Give the scientific name of Prawn.
›Reveal solutionSolution
The scientific (genus) name of prawn is Penaeus (e.g., Penaeus monodon, the giant tiger prawn).
Prawn is a crustacean belonging to phylum Arthropoda, class Crustacea, order Decapoda. It is commonly assigned to the genus Penaeus. A commonly cited full scientific (binomial) name for a widely farmed/consumed species is Penaeus monodon (the giant tiger prawn); other Penaeus s …
🎓Unlock everything free for 14 days
- ✓Full step-by-step solutions
- ✓Concept-first explanations
- ✓Methods, shortcuts & mistakes
- ✓PYQ mapping + timed mock tests
Full access for 14 days. No credit card required.