Animal Diversity and Classification

(d) Cartilaginous endoskeleton : Chondrichthyes

Chondrichthyes (sharks, rays) always have a cartilaginous endoskeleton. Not all mammals are viviparous (monotremes lay eggs), not all chordates have jaws (cyclostomes lack them), and reptiles generally have a 3-chambered heart but crocodiles have 4, so "always" fails.

(c) Warm blooded nature

Birds and mammals are both homeothermous (warm blooded). Viviparity is absent in birds, and lungs and an ossified endoskeleton are also shared by reptiles, amphibians and others, so the feature the question targets is warm bloodedness.

(b) Parapodia

Arthropoda show metameric segmentation, jointed appendages and a chitinous exoskeleton. Parapodia are lateral fleshy locomotory outgrowths of Annelida (e.g. Nereis).

(b) (iii) (i) (iv) (ii)

The housefly is classified as Family Muscidae, Order Diptera, Class Insecta, Phylum Arthropoda. So a-iii, b-i, c-iv, d-ii.

(c) All cyclostomes do not possess jaws and paired fins.

Cyclostomes (lampreys, hagfishes) are jawless with no paired fins. Some fishes (cartilaginous ones) have no operculum, monotremes are oviparous, and crocodiles have a four-chambered heart, so (a), (b), (d) are false.

(d) Petromyzon

Lampreys (Petromyzon) migrate to fresh water to spawn; the ammocoete larva metamorphoses and returns to the sea. Myxine, Eptatretus and Neomyxine are hagfishes, which are exclusively marine.

(c) N-acetyl glucosamine

Chitin is a long-chain polymer of N-acetyl glucosamine (a modified sugar). Keratin and chondroitin sulphate are not its building blocks, and D-glucosamine alone is not the repeating unit.

(c) Whale

Whales are mammals with a four-chambered heart and complete double circulation (separate pulmonary and systemic circuits). Frog and lizard have incompletely divided hearts, and a shark has a single circulation.

(b) Porifera

Sponges have a cellular grade of organisation with a body of cell meshwork, a spongocoel and canals lined by flagellated choanocytes that filter food, and indirect development with a larval stage. Cnidarians lack choanocytes.

(c) Torpedo

Torpedo (electric ray) is a marine cartilaginous fish with electric organs that can discharge current. Scoliodon is a dogfish shark, Pristis a sawfish and Trygon a sting ray (with a venomous sting, not electric).

(a) Cnidaria

Cnidaria includes marine forms (jellyfish, corals, sea anemones) and freshwater ones (Hydra). Echinoderms, ctenophores and cephalochordates (Branchiostoma) are exclusively marine.

(c) Sea-fan (Gorgonia)

Gorgonia is a cnidarian (animal), and animal cells lack a cell wall. Blue-green algae and cyanobacteria (the same group) have peptidoglycan walls, and Saccharomyces (yeast) has a chitin-glucan wall.

(c) regeneration

Planaria (flatworm, phylum Platyhelminthes) has remarkable regenerative power because of its neoblast stem cells; even a small cut piece can regrow a whole worm. It does not show metamorphosis or alternation of generation, and bioluminescence is not its feature.

(a) Petromyzon : Ectoparasite : Cyclostomata

Petromyzon (lamprey) is a jawless cyclostome that is an ectoparasite on fishes. Ichthyophis is an amphibian, not a reptile. Limulus (king crab) is an arthropod, not a fish. Adamsia (sea anemone) is radially symmetrical but belongs to Cnidaria, not Porifera.

(c) House fly, butterfly, tsetsefly, silverfish - Insecta

All four are insects with three pairs of legs. In (a), cuttlefish is a mollusc and silverfish is an insect. In (b), centipede and millipede are myriapods and spider and scorpion are arachnids. In (d), spiny anteater is a mammal (monotreme), not an echinoderm.

(c) Prawn, Scorpion, Locusta

Prawn (crustacean), scorpion (arachnid) and Locusta (insect) are all jointed-legged animals of phylum Arthropoda. The others mix phyla: Plasmodium/Amoeba (Protozoa) with mosquito (Arthropoda); earthworm (Annelida), pinworm (Nematoda), tapeworm (Platyhelminthes); sponge (Porifera), sea anemone (Cnidaria), starfish (Echinodermata).

(b) Silverfish

Silverfish (Lepisma) is a wingless insect, so it belongs to Arthropoda. Cuttlefish is a mollusc, while pufferfish and flying fish are true fishes (Chordata). The "fish" in the name is the trap.

(b) Trypanosoma

Trypanosoma is a flagellate protozoan causing sleeping sickness. Paramoecium is a ciliate, Entamoeba is an amoeboid protozoan, and Plasmodium is a sporozoan.

(c) Jointed appendages: Prawn, Centipede, Grasshopper

All three are arthropods, which have jointed appendages. In (a) tapeworm and starfish lack a typical respiratory system; in (b) Hydra is radially symmetrical and sea urchin is radial as an adult; in (d) liver fluke is not metamerically segmented.

(c) It migrates to the ocean for spawning

This is false. Petromyzon (lamprey) lives in the sea but migrates to fresh water for spawning, and larvae (ammocoetes) return to the ocean after metamorphosis. It has no scales, a circular jawless sucker mouth and a closed circulatory system.

(d) Bilateral

Echinoderm larvae are bilaterally symmetrical, and the adults become radially symmetrical (pentamerous). This is evidence that echinoderms evolved from bilateral ancestors.

(d) having two types of nuclei

Ciliates such as Paramecium have a macronucleus and a micronucleus. Pseudopodia belong to amoeboid protozoans, flagella to flagellates, and contractile vacuoles occur in other freshwater protozoans too, so these do not distinguish ciliates.

(a) Aves

Birds have a crop to store food and a gizzard to grind it. Reptiles, amphibians and bony fishes lack this combination.

(b) Chelone

Chelone (turtle) is a reptile and poikilothermic (cold-blooded). Camelus, Macropus (kangaroo) and Psittacula (parrot) are mammals and a bird, which are homeotherms.

(c) Earthworm

Earthworms show direct development with no larval stage. Moths undergo metamorphosis via caterpillar and pupa, tunicates have a tadpole larva that undergoes retrogressive metamorphosis, and starfish have a bipinnaria larva.

(a) Annelida, Arthropoda and Chordata

All three are bilaterally symmetrical, true coelomates (Chordata have a true coelom), have organ-system level organisation, and show segmentation (metamerism). Mollusca are also bilateral coelomates with organ-system organisation, but their body is not segmented (it has a head, foot and visceral hump), so any option with Mollusca is wrong.

(b) (a)-(iii), (b)-(iv), (c)-(ii), (d)-(i)

Pila (a mollusc) has a radula for feeding. Bombyx (silk moth, an insect) has Malpighian tubules for excretion. Pleurobrachia (a ctenophore) has comb plates for locomotion. Taenia (a flatworm) has flame cells for excretion.

(b) (a)-(iv), (b)-(i), (c)-(ii), (d)-(iii)

Locusta is a gregarious, polyphagous pest. Asterias (starfish) has radial adults and bilateral larvae. Scorpions breathe by book lungs, and Ctenoplana (a ctenophore) shows bioluminescence.

(d) (ii) and (iii)

In vertebrates the notochord is present only in the embryo and is replaced by the vertebral column. The CNS in chordates is dorsal and hollow. Statement (i) is wrong because in Urochordata the notochord is present only in the larval tail. Statement (iv) is wrong because the subphyla are Urochordata (Tunicata), Cephalochordata and Vertebrata, and Hemichordata is not a subphylum of Chordata.

(a) (a)-(ii), (b)-(iii), (c)-(iv), (d)-(i)

Cyclostomes have 6-15 pairs of gill slits. Chondrichthyes (cartilaginous fishes) have a heterocercal caudal fin. Osteichthyes have an air bladder. Trygon (sting ray) has a poisonous sting.

(b) Platyhelminthes

Flatworms are bilaterally symmetrical, triploblastic and acoelomate. Ctenophora are radially symmetrical. Aschelminthes are pseudocoelomate and Annelida are true coelomate.

(d) Both (A) and (R) are correct but (R) is not the correct explanation of (A)

All vertebrates have a notochord at some stage, so they are chordates, while urochordates and cephalochordates are chordates without vertebrae. R is also true, but vertebrates being chordates is due to the notochord's presence in the embryo, and replacement by the column does not explain why not all chordates are vertebrates.

(b) Pavo

Birds such as the peacock (Pavo) are uricotelic and excrete nitrogenous waste as uric acid in pellet or paste form, saving water. Hippocampus (fish) and Ornithorhynchus (mammal) are ammonotelic and ureotelic respectively, and Salamandra (amphibian) is mainly ureotelic.

(c) Kingdom, Phylum, Class, Order, Family, Genus, Species

The standard taxonomic hierarchy runs Kingdom, Phylum, Class, Order, Family, Genus, Species. Other options swap Phylum/Class/Order/Family, which breaks the order of inclusiveness.

(b) Pavo, Psittacula, Corvus

Crop and gizzard are digestive chambers of birds (peacock, parrot, crow). Catla (fish), Crocodilus, Chameleon, Bufo, Balaenoptera and Bangarus lack this arrangement; Columba is a bird but the other members of those sets are not.

(b) Hemichordata

Adult hemichordates (e.g. Balanoglossus) are bilaterally symmetrical. Adult ctenophores and coelenterates are radially symmetrical, and adult echinoderms show secondary pentamerous radial symmetry (their larvae are bilateral). So Hemichordata is the phylum in which radial symmetry is absent in adults.

(b) B and C only

Chordates have a closed circulatory system (B) and paired pharyngeal gill slits at some stage (C). A is wrong because the nerve cord is dorsal, hollow and single, not solid and double. D is wrong because the heart is ventral. E is wrong because chordates are coelomates, not pseudocoelomates.

(b) hairs, pinna and mammary glands

Hairs, external ear (pinna) and mammary glands are found only in mammals. A tympanic membrane is also present in amphibians, reptiles and birds, so it is not unique (option a is wrong). Mammals have a dicondylic skull, not monocondylic, and mostly direct development (options c and d are wrong).

(c) A only

Annelids are true coelomates. Poriferans are acoelomates, not pseudocoelomates (B is wrong). Aschelminthes are pseudocoelomates (C is wrong). Platyhelminthes are acoelomates (D is wrong).

(c) A-II, B-I, C-IV, D-III

Pleurobrachia is a ctenophore. The radula is a feeding organ of molluscs. The stomochord is characteristic of Hemichordata. The air bladder is found in bony fishes (Osteichthyes).

(c) A-III, B-I, C-II, D-IV

Pterophyllum is the angel fish, Myxine is the hag fish, Pristis is the saw fish and Exocoetus is the flying fish.

(d) B, D & E only

In non-chordates the notochord is absent (B), the heart, if present, is dorsal (D), and a post-anal tail is absent (E). Gill slits in the pharynx (A) and a dorsal central nervous system (C) are chordate features. Non-chordates have a ventral solid nerve cord.

(d) Ectoparasite

All living cyclostomes (lampreys and hagfishes) are ectoparasites on fishes. They have a sucking circular mouth without jaws and have no scales or paired fins.

(a) Both A and R are true and R is the correct explanation of A

All vertebrates possess a notochord at some stage, so they are chordates. Chordates also include Urochordata and Cephalochordata, which are not vertebrates. In vertebrates the notochord is replaced by a cartilaginous or bony vertebral column in adults, which explains why vertebrates are a subset of chordates.

(b) A and C Only

The water vascular system of echinoderms (tube feet, ampullae) helps in locomotion, respiration and the capture and transport of food. Excretion and digestion are not its functions, so B, D and E are wrong.

(a) Neophron

Neophron (vulture) is a bird, and birds have long bones that are hollow with air cavities (pneumatic), which lightens the body for flight. Hemidactylus (lizard), Macropus (kangaroo) and Ornithorhynchus (platypus) have solid, marrow-filled bones.

(d) (b), (c) and (e) are correct

Echinoderms are triploblastic and coelomate, roundworms have organ-system level organization, and the water vascular system is characteristic of echinoderms. Metagenesis is seen in cnidarians, not helminths, and ctenophore comb plates are for locomotion, not digestion.

(d) House fly

Musca domestica (house fly) belongs to family Muscidae of order Diptera. Fire fly (Lampyridae, Coleoptera), grasshopper (Acrididae) and cockroach (Blattidae) belong to other families.