Mix Examples - Animal Kingdom Questions in English

(D) The Assertion is incorrect because birds generally build nests primarily for laying eggs and rearing their young,not specifically for resting or sleeping at night. Many birds roost on branches or in cavities without building nests for that purpose.
The Reason is also incorrect because the Koel (Eudynamys scolopaceus) is a brood parasite that typically lays its eggs in the nest of a crow,not a tailor bird.
Therefore,both the Assertion and the Reason are incorrect.

(B) The correct matches are as follows:
$1$. $Ophiura$ (Brittle star) belongs to the phylum $Echinodermata$ $(a-iii)$.
$2$. $Physalia$ (Portuguese man-of-war) belongs to the phylum $Coelenterata$ (also known as $Cnidaria$) $(b-iv)$.
$3$. $Pinctada$ (Pearl oyster) belongs to the phylum $Mollusca$ $(c-i)$.
$4$. $Planaria$ (Flatworm) belongs to the phylum $Platyhelminthes$ $(d-ii)$.
Therefore, the correct sequence is $(a-iii), (b-iv), (c-i), (d-ii)$.

(A) The correct matches are as follows:

$(a)$ Operculum	$(viii)$ Osteichthyes
$(b)$ Parapodia	$(v)$ Annelida
$(c)$ Scales	$(iv)$ Reptilia
$(d)$ Comb plates	$(i)$ Ctenophora
$(e)$ Radula	$(ii)$ Mollusca
$(f)$ Hairs	$(vii)$ Mammalia
$(g)$ Choanocytes	$(iii)$ Porifera
$(h)$ Gill slits	$(vi)$ Cyclostomata and Chondrichthyes

(N/A) Parasitic animals are organisms that live on or inside the human body and derive nutrients from it. Some common examples include:

$S.No.$	Organism and Phylum
$(1)$	$Taenia solium$ (Platyhelminthes)
$(2)$	$Fasciola hepatica$ (Platyhelminthes)
$(3)$	$Ascaris lumbricoides$ (Aschelminthes)
$(4)$	$Wuchereria bancrofti$ (Aschelminthes)
$(5)$	$Ancylostoma$ (Aschelminthes)

(B) Direct Development: In this type of development, the organism hatching from the egg resembles the adult parent. There is no larval stage involved. Example: $Mammals$.
Indirect Development: In this type of development, the organism hatching from the egg does not resemble the adult parent. It passes through one or more larval stages before reaching the adult form. Examples: $Porifera$, $Arthropoda$.

(N/A)

Chondrichthyes	Osteichthyes
$(1)$ Exclusively marine.	$(1)$ Both marine and freshwater.
$(2)$ Skin covered with placoid scales.	$(2)$ Skin covered with cycloid or ctenoid scales.
$(3)$ Caudal fin is heterocercal.	$(3)$ Caudal fin is homocercal.
$(4)$ Endoskeleton is cartilaginous.	$(4)$ Endoskeleton is bony.
$(5)$ $5-7$ pairs of gills; operculum absent.	$(5)$ $4$ pairs of gills; operculum present.
$(6)$ Fertilization is internal.	$(6)$ Fertilization is external.
$(7)$ Mouth is ventral.	$(7)$ Mouth is terminal.
$(8)$ Examples: $Scoliodon$ (shark),$Pristis$ (sawfish).	$(8)$ Examples: $Hippocampus$ (sea horse),$Labeo$ (rohu).

(N/A) The following table provides a comparative summary of the key characteristics of various animal phyla:

Phylum	Level of Organization	Symmetry	Coelom	Segmentation	Digestive System	Circulatory System	Respiratory System	Distinctive Features
Porifera	Cellular	Various	Absent	Absent	Absent	Absent	Absent	Body with pores and canal system
Cnidaria	Tissue	Radial	Absent	Absent	Incomplete	Absent	Absent	Cnidoblasts present
Ctenophora	Tissue	Radial	Absent	Absent	Incomplete	Absent	Absent	Comb plates for locomotion
Platyhelminthes	Organ/Organ-system	Bilateral	Absent	Absent	Incomplete	Absent	Absent	Flat body,suckers
Aschelminthes	Organ-system	Bilateral	Pseudocoelomate	Absent	Complete	Absent	Absent	Often worm-shaped,elongated
Annelida	Organ-system	Bilateral	Coelomate	Present	Complete	Present	Present	Metameric segmentation
Arthropoda	Organ-system	Bilateral	Coelomate	Present	Complete	Present	Present	Exoskeleton of chitin,jointed appendages
Mollusca	Organ-system	Bilateral	Coelomate	Absent	Complete	Present	Present	External shell usually present
Echinodermata	Organ-system	Radial	Coelomate	Absent	Complete	Present	Present	Water vascular system
Hemichordata	Organ-system	Bilateral	Coelomate	Absent	Complete	Present	Present	Proboscis,collar,and trunk
Chordata	Organ-system	Bilateral	Coelomate	Present	Complete	Present	Present	Notochord,dorsal hollow nerve cord,gill slits

(A-D) The differences between Phylum $Platyhelminthes$ and Phylum $Aschelminthes$ are as follows:
$1$. Body Shape: $Platyhelminthes$ are dorso-ventrally flattened (flatworms),whereas $Aschelminthes$ are circular in cross-section (roundworms).
$2$. Coelom: $Platyhelminthes$ are acoelomate (lack a body cavity),while $Aschelminthes$ are pseudocoelomate (possess a false body cavity).
$3$. Digestive System: $Platyhelminthes$ possess an incomplete digestive system (single opening serving as both mouth and anus),while $Aschelminthes$ possess a complete digestive system with a well-developed muscular pharynx.
$4$. Excretory Organs: $Platyhelminthes$ utilize specialized cells called flame cells for osmoregulation and excretion. $Aschelminthes$ utilize an excretory pore or renette cells for the removal of body wastes.

(N/A) $(i)$ Poikilothermous: These are animals that do not maintain a constant body temperature and change their body temperature according to the surrounding environment. They are also known as cold-blooded animals.
$(ii)$ Homoiothermous: These are animals that maintain a constant body temperature regardless of the surrounding environment. They are also known as warm-blooded animals.

(A) $(i)$ Comb plates:
Location: Present in the phylum $Ctenophora$.
Function: They are ciliated structures that help in locomotion.
$(ii)$ Flame cells:
Location: Present in the phylum $Platyhelminthes$.
Function: They are specialized cells that help in osmoregulation and excretion.

(N/A) $(i)$ Location: In Phylum $Annelida$.
Function: Excretory organs.
$(ii)$ Location: In Phylum $Mollusca$.
Function: Contains feather-like gills for respiration and excretion.

(A) $(i)$ Water vascular system:
Location: It is a characteristic feature of the phylum $Echinodermata$.
Function: It plays a vital role in locomotion,capture and transport of food,and respiration.
$(ii)$ Cloaca:
Location: It is found in the posterior part of the body in amphibians,reptiles,birds,and some fishes.
Function: It serves as a common chamber for the opening of the digestive,reproductive,and urinary tracts.

(A) The body symmetry of animals is determined by the arrangement of body parts around a central axis.
$1$. Radial symmetry: In this type of symmetry,any plane passing through the central axis of the body divides the organism into two identical halves. Examples include Coelenterates,Ctenophores,and adult Echinoderms.
$2$. Bilateral symmetry: In this type of symmetry,the body can be divided into identical left and right halves in only one plane. Examples include Annelids and Arthropods.

(A) The correct matching is: $(a-5, b-3, c-2, d-1, e-6, f-4)$.
$(a)$ Amphibia - Dual habitat: They are adapted to live on both land and water.
$(b)$ Mammalia - Mammary gland: They possess milk-producing glands to nourish their young ones.
$(c)$ Chondrichthyes - Cartilaginous notochord: They have a persistent cartilaginous endoskeleton.
$(d)$ Osteichthyes - Air bladder: They possess an air bladder which regulates buoyancy.
$(e)$ Cyclostomata - Jawless,circular,sucking mouth: They have a circular mouth without jaws,used for suction.
$(f)$ Aves - Pneumatic bones: They have hollow,air-filled bones that reduce body weight for flight.

(A-5, B-1, C-3, D-4, E-2, F-6) The correct matches are as follows:
$(a)$ Pila belongs to the phylum Mollusca and is characterized by the $(5)$ Presence of shell.
$(b)$ Cockroach belongs to the phylum Arthropoda and is characterized by $(1)$ Jointed appendages.
$(c)$ Asterias (Starfish) belongs to the phylum Echinodermata and is characterized by the $(3)$ Water vascular system.
$(d)$ Torpedo is a cartilaginous fish that possesses a $(4)$ Electric organ.
$(e)$ Parrot is a bird (Aves) characterized by $(2)$ Perching behavior.
$(f)$ Dog fish (Scoliodon) is a cartilaginous fish characterized by the presence of $(6)$ Placoid scales.
Therefore,the correct sequence is: $(a-5, b-1, c-3, d-4, e-2, f-6)$.

(N/A) Chondrichthyes and Osteichthyes:
Chondrichthyes:
- They are marine animals with a streamlined body and cartilaginous endoskeleton.
- The mouth is located ventrally.
- The notochord is persistent throughout life.
- Gill slits are separate and without an operculum (gill cover).
- The skin is tough,containing minute placoid scales.
- Teeth are modified placoid scales that are backwardly directed.
- Their jaws are very powerful.
- These animals are predaceous.
- Due to the absence of an air bladder,they have to swim constantly to avoid sinking.
- The heart is two-chambered (one auricle and one ventricle).
- Some of them have electric organs (e.g.,$Torpedo$) and some possess a poison sting (e.g.,$Trygon$).
- They are cold-blooded (poikilothermous) animals.
- Sexes are separate. In males,pelvic fins bear claspers.
- They have internal fertilization and many are viviparous.
- Examples: $Scoliodon$ (Dog fish),$Pristis$ (Saw fish).
Osteichthyes:
- They include both marine and freshwater fishes with a bony endoskeleton.
- The body is streamlined. Mouth is mostly terminal.
- They have four pairs of gills which are covered by an operculum on each side.
- Skin is covered with cycloid/ctenoid scales.
- Air bladder is present which regulates buoyancy.
- Heart is two-chambered.
- They are cold-blooded animals.
- Sexes are separate. Fertilization is usually external. They are mostly oviparous and development is direct.
- Examples: $Hippocampus$ (Sea horse),$Labeo$ (Rohu).
$(b)$ Urochordata and Cephalochordata:
Urochordata (Tunicata):
- Notochord is present only in the larval tail.
- Examples: $Ascidia$,$Salpa$,$Doliolum$.
Cephalochordata:
- Notochord extends from head to tail region and is persistent throughout their life.
- Examples: $Branchiostoma$ (Amphioxus or Lancelet).

(N/A) Aves and mammals: Both are warm-blooded (homeothermic) animals and possess a four-chambered heart.
$(b)$ $A$ frog and crocodile: Both can live in both terrestrial and aquatic habitats. Both utilize lungs for respiration.
$(c)$ $A$ turtle and Pila: Both possess a hard protective shell covering their body. Both are oviparous (egg-laying) animals.

(N/A) Ichthyophis (a limbless amphibian).
$(b)$ Frog (an ectothermic or cold-blooded animal).
$(c)$ Parrot (an endothermic or warm-blooded animal).
$(d)$ Python (a reptile with dry and cornified skin).
$(e)$ Sycon (a sponge belonging to Phylum Porifera).
$(f)$ Obelia (a cnidarian possessing cnidoblasts).

(N/A) Chimpanzee (or any mammal like Human or Whale).
$(b)$ Stingray (Trygon).
$(c)$ Electric ray (Torpedo).
$(d)$ Air bladder (Swim bladder).
$(e)$ Obelia.
$(f)$ Platypus (Ornithorhynchus).

(B) The term 'Frugivorous' refers to organisms that primarily feed on fruits.
Examples of frugivorous animals include monkeys,fruit bats,and certain species of birds like hornbills.

(N/A) Amphibia:
- As the name indicates (Gr.,Amphi: dual,bios: life),amphibians can live in aquatic as well as terrestrial habitats.
- Most of them have two pairs of limbs.
- Body is divisible into head and trunk.
- Tail may be present in some.
- The amphibian skin is moist (without scales).
- The eyes have eyelids.
- $A$ tympanum represents the ear.
- Alimentary canal,urinary and reproductive tracts open into a common chamber called cloaca which opens to the exterior.
- Respiration is by gills,lungs and through skin.
- The heart is three-chambered (two auricles and one ventricle).
- These are cold-blooded (poikilothermous) animals.
- Sexes are separate.
- Fertilisation is external.
- They are oviparous and development is direct or indirect.
- Examples: Bufo (Toad),Rana (Frog),Hyla (Tree frog),Salamandra (Salamander),Ichthyophis (Limbless amphibia).
Reptilia:
- The class name refers to their creeping or crawling mode of locomotion (Latin,repere or reptum: to creep or crawl).
- They are mostly terrestrial animals and their body is covered by dry and cornified skin,epidermal scales or scutes.
- They do not have external ear openings. Tympanum represents ear.
- Limbs,when present,are two pairs.
- Heart is usually three-chambered,but four-chambered in crocodiles.
- Reptiles are poikilotherms.
- Snakes and lizards shed their scales as skin cast.
- Sexes are separate.
- Fertilisation is internal.
- They are oviparous and development is direct.
- Examples: Chelone (Turtle),Testudo (Tortoise),Chameleon (Tree lizard),Calotes (Garden lizard),Crocodilus (Crocodile),Alligator (Alligator),Hemidactylus (Wall lizard),Poisonous snakes - Naja (Cobra),Bangarus (Krait),Vipera (Viper).

(A) $(i)$ Cnidarians exhibit radial symmetry,whereas Poriferans are mostly asymmetrical. Therefore,the correct term is radial symmetry.
$(ii)$ Annelids are true coelomates,whereas Platyhelminthes (flatworms) lack a body cavity and are therefore acoelomates.

(B) $(i)$ In Cnidaria,the body has a single opening called the hypostome (or mouth) through which water and food enter and waste exits. Thus,the correct term is hypostome.
(ii) In Aschelminthes (roundworms),the excretory system consists of an excretory pore that removes body wastes from the body cavity. Thus,the correct term is excretory pore.

(A) $(i)$ In aquatic annelids like Nereis,lateral appendages called parapodia are present,which help in swimming. Similarly,in arthropods,the characteristic feature is the presence of jointed appendages.
$(ii)$ In annelids,the excretory organs are nephridia. In arthropods,the primary excretory organs are Malpighian tubules.

(A) $(i)$ In Porifera,the body wall contains specialized cells called Choanocytes (collar cells). Similarly,in Platyhelminthes,the specialized cells for excretion and osmoregulation are called Flame cells (protonephridia).
$(ii)$ Chondrichthyes (cartilaginous fishes) possess Placoid scales. Similarly,Osteichthyes (bony fishes) possess Cycloid or Ctenoid scales.

(A) $(i)$ Metamerism (true segmentation) is a characteristic feature of the phylum $Annelida$,where the body is externally and internally divided into segments called metameres.
$(ii)$ In sponges $(Porifera)$,asexual reproduction occurs through internal buds known as $Gemmules$,which help in perennation and dispersal.

(A) $(i)$ Birds are oviparous animals that lay eggs,which is a characteristic feature of the class $Aves$.
$(ii)$ Cartilaginous fishes (class $Chondrichthyes$) are characterized by having $5-7$ pairs of gill slits that are separate and without an operculum (gill cover).
Therefore,the correct combination is $(i)$ Oviparous and $(ii)$ Without operculum.

(C) $(i)$ $Pleurobrachia$ and $Ctenoplana$ are well-known examples of the phylum $Ctenophora$ (comb jellies).
$(ii)$ $Spongilla$ is a well-known example of a freshwater sponge,whereas $Sycon$ $(Scypha)$ and $Euspongia$ ($Bath$ $sponge$) are typically marine.

(A) $(i)$ Platyhelminthes (flatworms) are acoelomate,meaning they lack a body cavity.
$(ii)$ Cnidarians (coelenterates) exhibit radial symmetry,where the body can be divided into identical halves by any plane passing through the central axis.

(B) $6-15$ pairs of gill slits are a characteristic feature of Cyclostomes $(ii)$.
$(b)$ Heterocercal caudal fin is a characteristic feature of Chondrichthyes $(iii)$.
$(c)$ Air Bladder is present in Osteichthyes $(iv)$ to regulate buoyancy.
$(d)$ Poison sting is found in Trygon $(i)$,which belongs to Chondrichthyes.
Therefore,the correct matching is $(a)-(ii), (b)-(iii), (c)-(iv), (d)-(i)$.

(C) The correct matching is as follows:
$(a)$ Gregarious,polyphagous pest: $(iv)$ $Locusta$ (Locusts are known for their swarming behavior and feeding on various crops).
$(b)$ Adult with radial symmetry and larva with bilateral symmetry: $(i)$ $Asterias$ (Echinoderms like starfish exhibit radial symmetry in adults but bilateral symmetry in larvae).
$(c)$ Book lungs: $(ii)$ $Scorpion$ (Scorpions are arachnids that use book lungs for respiration).
$(d)$ Bioluminescence: $(iii)$ $Ctenoplana$ (Ctenophores are well-known for the property of bioluminescence).
Therefore,the correct sequence is $(a)-(iv), (b)-(i), (c)-(ii), (d)-(iii)$,which corresponds to option $(C)$.

(B) The correct matches are as follows:
$(a)$ Gregarious pest: $(iv)$ Locusta (a type of locust).
$(b)$ Radial symmetry in adults and bilateral symmetry in larvae: $(i)$ Asterias (Starfish,belonging to Echinodermata).
$(c)$ Book lungs: $(ii)$ Scorpion (Arthropoda,Arachnida).
$(d)$ Bioluminescence: $(iii)$ Ctenoplana (Ctenophora).
Therefore,the correct sequence is $(a)-(iv), (b)-(i), (c)-(ii), (d)-(iii)$.

(A) $6-15$ pairs of gill slits are characteristic of $Petromyzon$ (Cyclostomata).
$(b)$ Heterocercal caudal fin is a characteristic feature of cartilaginous fishes $(Chondrichthyes)$.
$(c)$ Air bladder is present in bony fishes $(Osteichthyes)$ to regulate buoyancy.
$(d)$ Poison sting is found in $Trygon$ (Sting ray),which belongs to $Chondrichthyes$.
Therefore,the correct matching is $(a)-(ii), (b)-(iii), (c)-(iv), (d)-(i)$.

(B) An endoparasite is an organism that lives inside the body of its host.
$A$. Tapeworm (Platyhelminthes) lives in the intestine of humans.
$B$. Amphidrus is not a recognized endoparasite; it is likely a distractor or a misspelling of a non-parasitic organism.
$C$. Plasmodium is an intracellular parasite that causes malaria in humans.
$D$. Entamoeba histolytica is an intestinal parasite that causes amoebiasis.
Therefore,Amphidrus is the correct answer as it is not an endoparasite.

(C) The tiger $(Panthera \text{ } tigris)$ has several recognized subspecies, including the Bali tiger $(P. \text{ } t. \text{ } balica)$, Javan tiger $(P. \text{ } t. \text{ } sondaica)$, and Caspian tiger $(P. \text{ } t. \text{ } virgata)$.
$A$ Liger is a hybrid offspring of a male lion $(Panthera \text{ } leo)$ and a female tiger $(Panthera \text{ } tigris)$.
Therefore, a Liger is not a subspecies of a tiger, but rather a cross-species hybrid.

(B) The correct matching is as follows:
$(a)$ Platyhelminthes: $(iii)$ Bilateral symmetry with an incomplete digestive system (single opening).
$(b)$ Echinoderms: $(iv)$ Radial symmetry (in adults) with indirect development (larval stage present).
$(c)$ Hemichordates: $(i)$ Cylindrical body with no segmentation (proboscis,collar,and trunk).
$(d)$ Aves: $(ii)$ Warm-blooded animals (homeotherms) with direct development.
Therefore,the correct sequence is $(a)-(iii), (b)-(iv), (c)-(i), (d)-(ii)$.

(D) The correct matching is as follows:
$(a)$ $Aptenodytes$ is commonly known as the Penguin,which belongs to the class $Aves$.
$(b)$ $Pteropus$ is commonly known as the Flying fox,which belongs to the class $Mammalia$.
$(c)$ $Pterophyllum$ is commonly known as the Angel fish,which belongs to the class $Osteichthyes$.
$(d)$ $Petromyzon$ is commonly known as the Lamprey,which belongs to the class $Cyclostomata$.
Therefore,the correct sequence is $(a)-(iv), (b)-(i), (c)-(ii), (d)-(iii)$. Thus,option $(D)$ is correct.

(C) $Pristis$ (Sawfish) belongs to the class $Chondrichthyes$ (cartilaginous fishes),which typically possess a ventral mouth.
$Catla$ (Carp) belongs to the class $Osteichthyes$ (bony fishes),which typically possess a terminal mouth.
Therefore,the correct difference is that $Pristis$ has a ventral mouth,while $Catla$ has a terminal mouth.

(A) The correct option is $A$.
$1$. Amphibia includes animals like Frog (Rana),Salamander,Bufo (Toad),and Ichthyophis (limbless amphibian).
$2$. Option $B$ is incorrect because Hyla is an amphibian,not a reptile.
$3$. Option $C$ is incorrect because Balaenoptera (Blue whale) and Flying fox (Pteropus) are mammals,not birds.
$4$. Option $D$ is incorrect because Ancylostoma (hookworm) is an Aschelminthes and Nereis is an Annelid,not Arthropods.

(D) Reptiles differ from amphibians in several key aspects:
$1$. Skin: Amphibians possess smooth,moist skin that lacks scales,whereas reptiles have dry,cornified skin covered by epidermal scales or scutes.
$2$. Heart Structure: Most amphibians have a $3$-chambered heart ($2$ atria and $1$ ventricle). In contrast,most reptiles have a $3$-chambered heart,but it is partially divided,and crocodilians possess a $4$-chambered heart,representing a more advanced circulatory system.
$3$. Development Stages: Amphibians typically undergo metamorphosis,often involving an aquatic larval stage (e.g.,tadpole). Reptiles exhibit direct development,where the young resemble the adults and do not undergo a larval stage.

(B) Sea fan $(Gorgonia)$ belongs to phylum $Coelenterata$ (Cnidaria),whereas sea lily $(Antedon)$,sea cucumber $(Cucumaria)$,and sea urchin $(Echinus)$ belong to phylum $Echinodermata$.

(C) $Dugesia$ (Planaria) is a free-living flatworm.
$Pheretima$ (earthworm) and $Nereis$ are free-living annelids.
$Fasciola$ (liver fluke),$Taenia$ (tapeworm),and $Ancylostoma$ (hookworm) are all parasitic organisms.
Therefore,the group consisting entirely of parasitic animals is $Fasciola - Taenia - Ancylostoma$.

(C) The correct statement is that the earthworm ($Pheretima$ $posthuma$) is metamerically segmented.
Earthworms belong to the phylum $Annelida$,which is characterized by true metameric segmentation.
Birds are homeothermic (warm-blooded),not poikilothermic.
Flatworms $(Platyhelminthes)$ are acoelomate,not coelomic.
Fishes are bilaterally symmetrical,not radially symmetrical.

(C) Flame cells are the specialized excretory structures found in the phylum Platyhelminthes (flatworms).
$Ascaris$ belongs to the phylum Aschelminthes (roundworms), which uses a renette cell or an excretory pore system for excretion, not flame cells.
Therefore, the pair $Ascaris - \text{Flame cell}$ is incorrectly matched.

(A) Solenocytes (also known as flame cells) are specialized excretory structures found in Platyhelminthes.
Nephridia are the tubular excretory organs found in Annelida.
Both structures serve the function of excretion and osmoregulation in their respective phyla.

(D) $Annelida$ represents a significant evolutionary advancement over $Nematoda$ due to several key features:
$1$. $Annelids$ possess a true coelom (eucoelom),which is a body cavity lined by mesoderm,whereas $Nematodes$ have a pseudocoelom.
$2$. $Annelids$ exhibit metameric segmentation,meaning their body is divided into repeating segments both externally and internally.
$3$. $Annelids$ possess a closed circulatory system,which is more efficient than the fluid-filled body cavity transport seen in $Nematodes$.
Therefore,all the listed features represent advancements.

(C) The features mentioned (Diploblastic,Acoelomate,and Radial symmetry) are characteristic of the phyla $Coelenterata$ (Cnidaria) and $Ctenophora$.
$1.$ $Adamsia$ (Sea anemone) belongs to the phylum $Coelenterata$.
$2.$ $Beroe$ belongs to the phylum $Ctenophora$.
$3.$ $Meandrina$ (Brain coral) belongs to the phylum $Coelenterata$.
All these organisms exhibit radial symmetry,are diploblastic,and lack a body cavity (acoelomate).

(B) Class-$Amphibia$ and class-$Reptilia$ share the following features:
$1$. Both classes possess a tympanum,which represents the ear.
$2$. Animals of both classes are cold-blooded or poikilotherms.
$3$. They usually have a three-chambered heart,with the exception of crocodiles in class-$Reptilia$ which have a four-chambered heart.

(C) The levels of organization in the animal kingdom are classified as follows:
$1$. Porifera exhibit a cellular level of organization.
$2$. Cnidaria and Ctenophora exhibit a tissue level of organization.
$3$. Platyhelminthes and higher phyla exhibit an organ or organ-system level of organization.
$4$. Annelida, Arthropoda, Mollusca, Echinodermata, and Chordata exhibit an organ-system level of organization.
Therefore, the pair $Annelida - \text{Organ level}$ is incorrect because Annelida possesses an organ-system level of organization.

(C) $Porifera$ exhibits cellular level of organization.
$Cnidaria$ exhibits tissue level of organization.
$Annelida$ exhibits organ-system level of organization,not just organ level.
$Mollusca$ exhibits organ-system level of organization.
Therefore,the incorrectly matched pair is $Annelida$ - Organ level only.