Arthropoda, Mollusca and Echinodermata MCQ Quiz - Objective Question with Answer for Arthropoda, Mollusca and Echinodermata - Download Free PDF

The correct answer is A and C Only

Concept:

• Echinoderms have an endoskeleton of calcareous ossicles and, hence, the name Echinodermata (Spiny bodied)
• All are marine with organ-system level of organisation.
• The adult echinoderms are radially symmetrical but larvae are bilaterally symmetrical.
• They are triploblastic and coelomate animals.
• Digestive system is complete with mouth on the lower (ventral) side and anus on the upper (dorsal) side.
• The most distinctive feature of echinoderms is the presence of water vascular system which helps in locomotion, capture and transport of food and respiration.
• An excretory system is absent. Sexes are separate.
• Reproduction is sexual. Fertilisation is usually external.
• Development is indirect with free-swimming larva.
• Examples: Asterias (Star fish), Echinus (Sea urchin), Antedon (Sea lily), Cucumaria (Sea cucumber) and Ophiura (Brittle star).

Explanation:

• Role of the Water Vascular System:
  • Respiration: The water vascular system facilitates gaseous exchange by circulating water through structures like tube feet and dermal branchiae, allowing oxygen uptake and carbon dioxide release.
  • Locomotion: The tube feet, powered by the water vascular system, create suction to help the organism move and adhere to surfaces. This is critical for activities like crawling and climbing in their marine environment.
  • Capture and Transport of Food: In some echinoderms, the water vascular system aids in handling food. For example, the tube feet help starfish pry open bivalve shells or pass food particles toward the mouth

The correct answer is They possess a closed circulatory system.

Explanation:

• Hemichordata was earlier considered as a sub-phylum under phylum Chordata. But now it is placed as a separate phylum under non-chordata.
• Hemichordates have a rudimentary structure in the collar region called stomochord, a structure similar to notochord.
• This phylum consists of a small group of worm-like marine animals with organ-system level of organisation.
• They are bilaterally symmetrical, triploblastic and coelomate animals.
• The body is cylindrical and is composed of an anterior proboscis, a collar and a long trunk (Figure 4.15).
• The circulatory system is of open type.
• Respiration takes place through gills.
• Excretory organ is proboscis gland. Sexes are separate.
• Fertilisation is external.
• Development is indirect.
• Examples: Balanoglossus and Saccoglossus.

The correct answer is Four

Characteristics of Mollusca:

• Mollusca is the second largest animal phylum
• Molluscs are terrestrial or aquatic (marine or fresh water) having an organ-system level of organisation.
• They are bilaterally symmetrical, triploblastic and coelomate animals.
• Body is covered by a calcareous shell and is unsegmented with a distinct head, muscular foot and visceral hump.
• A soft and spongy layer of skin forms a mantle over the visceral hump.
• The space between the hump and the mantle is called the mantle cavity in which feather like gills are present.
• They have respiratory and excretory functions.
• The anterior head region has sensory tentacles.
• The mouth contains a file-like rasping organ for feeding, called radula.

Explanation

The correct statements for Mollusca are:

1. Body covered by a calcareous shell
2. Unsegmented body with distinct head, muscular foot, and visceral hump
3. Presence of gills in the mantle cavity
4. They are usually dioecious and oviparous with indirect development.

The incorrect statements are:

1. Mollusks do not have jointed appendages. This characteristic belongs to arthropods. Mollusks typically have a muscular foot and sometimes tentacles, but these are not jointed.
2. The sensory tentacles in mollusks are typically located on the anterior head region rather than the posterior. Tentacles are important for sensation and feeding in these animals.

Explanation:

• Option 1: Centipede, millipede, spider, scorpion-Insecta - INCORRECT

​Centipede:

• PHYLUM - Arthropoda [Thick chitinous cuticle as an exoskeleton and jointed appendages.]
• CLASS - Chilopoda [Hundred-legged with body divisible into head and trunk.]

Millipede:

• PHYLUM - Arthropoda [Thick chitinous cuticle as an exoskeleton and jointed appendages.]
• CLASS - Diplopoda [Thousand-legged with body divisible into a head, thorax, and abdomen.]

Spider:

• PHYLUM - Arthropoda [Thick chitinous cuticle as an exoskeleton and jointed appendages.]
• CLASS - Arachnida [Cephalothorax with six pairs of appendages.]

Scorpion:

• PHYLUM - Arthropoda [Thick chitinous cuticle as an exoskeleton and jointed appendages.]
• CLASS - Arachnida [Cephalothorax with six pairs of appendages.]​

​Option 2: House fly, butterfly, tsetse fly, silverfish-Insecta - CORRECT

​​​House fly:

• PHYLUM - Arthropoda [Thick chitinous cuticle as an exoskeleton and jointed appendages.]
• CLASS - Insecta [Head bears a pair of compound eyes, a pair of antennae, and mouth parts adapted for chewing, biting, piercing sucking, etc.]

Butterfly:

• PHYLUM - Arthropoda [Thick chitinous cuticle as an exoskeleton and jointed appendages.]
• CLASS - Insecta [Head bears a pair of compound eyes, a pair of antennae, and mouth parts adapted for chewing, biting, piercing, sucking, etc.]

Tsetse fly:

• PHYLUM - Arthropoda [Thick chitinous cuticle as an exoskeleton and jointed appendages.]
• CLASS - Insecta [Head bears a pair of compound eyes, a pair of antennae and mouth parts adapted for chewing, biting, piercing, sucking, etc.]

Silverfish:

• PHYLUM - Arthropoda [Thick chitinous cuticle as an exoskeleton and jointed appendages.]
• CLASS - Insecta [Head bears a pair of compound eyes, a pair of antennae, and mouth parts adapted for chewing, biting, piercing, sucking, etc.]

Option 3: Spiny anteater, sea urchin, sea cucumber- Echinodermata - INCORRECT

​​Spiny anteater:​

• ​PHYLUM - Chordata [Presence of dorsal tubular nerve cord, pharyngeal gill slits, and notochord at some stage of development.]
• SUB-PHYLUM - Vertebrata [ Presence of vertebral column]
• CLASS - Mammalia [Presence of mammary gland]

Sea urchin:

• ​PHYLUM - Echinodermata [Marine animal showing usually pentamerous radial symmetry with podia or tube feet projecting out of the body.]
• CLASS - Echinoidea [Body is spherical, disc-like, oval, or heart-shaped with an endoskeleton made up of closely fitted calcareous plates with movable spines.]

​Sea cucumber:​

• ​PHYLUM - Echinodermata [Marine animal showing usually pentamerous radial symmetry with podia or tube feet projecting out of the body.]
• ​CLASS - Holothuroidea [Endoskeleton is reduced to microscopic spicules or plates that are embedded in the body wall. Mouth surrounded by a set of tentacles.]

​​Option 4: Flying fish, cuttlefish, silverfish- Pisces - INCORRECT

​​Flying fish:​

• ​PHYLUM - Chordata [Presence of dorsal tubular nerve cord, pharyngeal gill slits, and notochord at some stage of development.]
• SUB-PHYLUM - Vertebrata [ Presence of vertebral column]
• SUPER CLASS - Pisces [Aquatic and bears fins]
• CLASS - Osteichthyes [Marine or freshwater fish with bony exoskeleton.

Cuttlefish:​

• ​PHYLUM - Mollusca [Body is soft, unsegmented and bilaterally symmetrical. The body consists of a head, foot, mantle, and visceral mass.]
• CLASS - Cephalopoda [Shell embedded in the mantle. The foot altered into a series of tentacles encircling the mouth.]

​​​Silverfish:​

• PHYLUM - Arthropoda [Thick chitinous cuticle as an exoskeleton and jointed appendages.]
• CLASS - Insecta [Head bears a pair of compound eyes, a pair of antennae and mouth parts adapted for chewing, biting, piercing, sucking,etc.]

So the correct answer is option 2 (House fly, butterfly, tsetse fly, silverfish- Insecta).

The correct answer is Excretory.
Key Points

• Unio is a genus of medium-sized freshwater mussels, aquatic bivalve mollusks (Phylum Mollusca) in the family Unionidae, the River mussels.
• Unio is the type genus of the family Unionidae.

Keber's organ

• It is the excretory organ in certain organisms like molluscs (which includes - Mussels, snail, octopus, clams etc.).
• It is otherwise also called as 'pericardial gland'.
• Keber's organ function is similar to that of the kidney and are present in addition to the kidneys (organ of Bojanus). 
• Structure:
  • ​It is a large, reddish-brown glandular mass.
• Location:
  • It may be over the auricle surface (articular glands), on the pericardium (pericardial glands), or in both positions. i.e., situated antero-lateral to the pericardium into which it discharges the waste material.
  • They are collected from that point by the kidney.
• Function:
  • The organ is responsible for the removal of nitrogenous wastes.
  • The wastes are excreted into pericardium from where these are collected by the 'organ of Bojanus' to be discharged outside the body. 

• Pericardial glands of bivalves have revealed that these consist of podocytes where the base of cytoplasmic extensions gives rise to numerous pedicels.

• These form a net with slits through which the fluid is filtered.

Additional Information

Unio: Organs and their function

• Excretory organ: The excretory system of Unio includes a pair of kidneys (organs of Bojanus), a pericardial gland (Keber's organ).
• Vascular: The blood vascular system is well developed and is of open type. It comprises the blood, heart, pericardium, arteries, sinuses, and veins.
• Digestive: The liver is the only digestive gland that surrounds the stomach. It secretes digestive enzymes and its cells are capable of ingesting food particles where intracellular digestion (i.e. digestion occurs in a cell) also occurs. 
• Reproductive: In Unio, the sexes are separate (dioecious) but there is no sexual dimorphism.

About Phylum Mollusca

• Mollusks are terrestrial or aquatic (marine or freshwater) animals having a calcareous shell.
• The body is covered by a calcareous shell and is un-segmented with a distinct head, muscular foot, and visceral hump.
• A soft and spongy layer of skin forms a mantle over the visceral hump.

Unio (Fresh-water Mussels)

• It belongs to bivalve molluscs.
• The animal is sedentary and eventually settles down on the bottom of the river or the lake through the mud or sand.

• Limulus does not belong to the Phylum Annelida.
• Annelida are bilaterally symmetrical with an organ-system level of body organization.
• Limulus belong to the Phylum Arthropoda which is the largest phylum of Animalia which includes insects.

Additional Information

• Nereis is a genus of polychaete worms in the family Nereididae.
• It comprises many species, most of which are marine. Nereis possess setae and parapodia for locomotion. 
• The parapodia also help in swimming
• Pheretima also called “Earthworm” belongs to Phylum Annelida
• The earthworm is a reddish-brown terrestrial invertebrate.
• The common Indian earthworms are Pheretima and Lumbricus.
• They inhabit the upper layer of the moist soil.
• During day time, they live in burrows made by boring and swallowing the soil.
• Hirudinaria is an example of Annelida Phylum.
• The annelids are also known as the ringed worms and are bilaterally symmetrical, triploblastic, coelomate, invertebrate organisms

The correct answer is Excretory.
Key Points

• Unio is a genus of medium-sized freshwater mussels, aquatic bivalve mollusks (Phylum Mollusca) in the family Unionidae, the River mussels.
• Unio is the type genus of the family Unionidae.

Keber's organ

• It is the excretory organ in certain organisms like molluscs (which includes - Mussels, snail, octopus, clams etc.).
• It is otherwise also called as 'pericardial gland'.
• Keber's organ function is similar to that of the kidney and are present in addition to the kidneys (organ of Bojanus). 
• Structure:
  • ​It is a large, reddish-brown glandular mass.
• Location:
  • It may be over the auricle surface (articular glands), on the pericardium (pericardial glands), or in both positions. i.e., situated antero-lateral to the pericardium into which it discharges the waste material.
  • They are collected from that point by the kidney.
• Function:
  • The organ is responsible for the removal of nitrogenous wastes.
  • The wastes are excreted into pericardium from where these are collected by the 'organ of Bojanus' to be discharged outside the body. 

• Pericardial glands of bivalves have revealed that these consist of podocytes where the base of cytoplasmic extensions gives rise to numerous pedicels.

• These form a net with slits through which the fluid is filtered.

Additional Information

Unio: Organs and their function

• Excretory organ: The excretory system of Unio includes a pair of kidneys (organs of Bojanus), a pericardial gland (Keber's organ).
• Vascular: The blood vascular system is well developed and is of open type. It comprises the blood, heart, pericardium, arteries, sinuses, and veins.
• Digestive: The liver is the only digestive gland that surrounds the stomach. It secretes digestive enzymes and its cells are capable of ingesting food particles where intracellular digestion (i.e. digestion occurs in a cell) also occurs. 
• Reproductive: In Unio, the sexes are separate (dioecious) but there is no sexual dimorphism.

About Phylum Mollusca

• Mollusks are terrestrial or aquatic (marine or freshwater) animals having a calcareous shell.
• The body is covered by a calcareous shell and is un-segmented with a distinct head, muscular foot, and visceral hump.
• A soft and spongy layer of skin forms a mantle over the visceral hump.

Unio (Fresh-water Mussels)

• It belongs to bivalve molluscs.
• The animal is sedentary and eventually settles down on the bottom of the river or the lake through the mud or sand.

Concept:

• The animal kingdom is divided into different phyla based on symmetry, level of organization, presence/absence of coelom, etc.
•  Kingdom Animalia is divided into 11 different phyla.

Explanation:

Let us see a few organisms and their phyla:

Sl. No	Organism	Commonly known as	Phylum	Image
1	Physalia	Portuguese man-of-war	It belongs to Phylum Cnidaria. The name comes from its resemblance to the warship, the Portuguese man-of-war. These animals are mostly aquatic and have cnidoblasts on their tentacles and body. Cnidoblast provides protection and helps in anchorage and capture of prey.
2	Limulus	King crab	It belongs to Phylum Arthropoda. It is a  marine arthropod. It has changed very little compared to its millions of years old ancestors hence, it is called a living fossil.
3	Ancylostoma	Hookworm	It belongs to Phylum Aschelminthes. The body of roundworms is circular in cross-section. They are mostly parasitic and live inside the body of the host.
4	Pinctada	Pearl oyster	It belongs to Phylum Mollusca. It is mostly marine. It makes a shell (from aragonite, and conchiolin)  around its body for protection.

So, the correct answer is option 4, a - ii, b - iii, c - iv, d - i.

The correct answer is A and C Only

Concept:

• Echinoderms have an endoskeleton of calcareous ossicles and, hence, the name Echinodermata (Spiny bodied)
• All are marine with organ-system level of organisation.
• The adult echinoderms are radially symmetrical but larvae are bilaterally symmetrical.
• They are triploblastic and coelomate animals.
• Digestive system is complete with mouth on the lower (ventral) side and anus on the upper (dorsal) side.
• The most distinctive feature of echinoderms is the presence of water vascular system which helps in locomotion, capture and transport of food and respiration.
• An excretory system is absent. Sexes are separate.
• Reproduction is sexual. Fertilisation is usually external.
• Development is indirect with free-swimming larva.
• Examples: Asterias (Star fish), Echinus (Sea urchin), Antedon (Sea lily), Cucumaria (Sea cucumber) and Ophiura (Brittle star).

Explanation:

• Role of the Water Vascular System:
  • Respiration: The water vascular system facilitates gaseous exchange by circulating water through structures like tube feet and dermal branchiae, allowing oxygen uptake and carbon dioxide release.
  • Locomotion: The tube feet, powered by the water vascular system, create suction to help the organism move and adhere to surfaces. This is critical for activities like crawling and climbing in their marine environment.
  • Capture and Transport of Food: In some echinoderms, the water vascular system aids in handling food. For example, the tube feet help starfish pry open bivalve shells or pass food particles toward the mouth

• Limulus does not belong to the Phylum Annelida.
• Annelida are bilaterally symmetrical with an organ-system level of body organization.
• Limulus belong to the Phylum Arthropoda which is the largest phylum of Animalia which includes insects.

Additional Information

• Nereis is a genus of polychaete worms in the family Nereididae.
• It comprises many species, most of which are marine. Nereis possess setae and parapodia for locomotion. 
• The parapodia also help in swimming
• Pheretima also called “Earthworm” belongs to Phylum Annelida
• The earthworm is a reddish-brown terrestrial invertebrate.
• The common Indian earthworms are Pheretima and Lumbricus.
• They inhabit the upper layer of the moist soil.
• During day time, they live in burrows made by boring and swallowing the soil.
• Hirudinaria is an example of Annelida Phylum.
• The annelids are also known as the ringed worms and are bilaterally symmetrical, triploblastic, coelomate, invertebrate organisms

The correct answer is Excretory.
Key Points

• Unio is a genus of medium-sized freshwater mussels, aquatic bivalve mollusks (Phylum Mollusca) in the family Unionidae, the River mussels.
• Unio is the type genus of the family Unionidae.

Keber's organ

• It is the excretory organ in certain organisms like molluscs (which includes - Mussels, snail, octopus, clams etc.).
• It is otherwise also called as 'pericardial gland'.
• Keber's organ function is similar to that of the kidney and are present in addition to the kidneys (organ of Bojanus). 
• Structure:
  • ​It is a large, reddish-brown glandular mass.
• Location:
  • It may be over the auricle surface (articular glands), on the pericardium (pericardial glands), or in both positions. i.e., situated antero-lateral to the pericardium into which it discharges the waste material.
  • They are collected from that point by the kidney.
• Function:
  • The organ is responsible for the removal of nitrogenous wastes.
  • The wastes are excreted into pericardium from where these are collected by the 'organ of Bojanus' to be discharged outside the body. 

• Pericardial glands of bivalves have revealed that these consist of podocytes where the base of cytoplasmic extensions gives rise to numerous pedicels.

• These form a net with slits through which the fluid is filtered.

Additional Information

Unio: Organs and their function

• Excretory organ: The excretory system of Unio includes a pair of kidneys (organs of Bojanus), a pericardial gland (Keber's organ).
• Vascular: The blood vascular system is well developed and is of open type. It comprises the blood, heart, pericardium, arteries, sinuses, and veins.
• Digestive: The liver is the only digestive gland that surrounds the stomach. It secretes digestive enzymes and its cells are capable of ingesting food particles where intracellular digestion (i.e. digestion occurs in a cell) also occurs. 
• Reproductive: In Unio, the sexes are separate (dioecious) but there is no sexual dimorphism.

About Phylum Mollusca

• Mollusks are terrestrial or aquatic (marine or freshwater) animals having a calcareous shell.
• The body is covered by a calcareous shell and is un-segmented with a distinct head, muscular foot, and visceral hump.
• A soft and spongy layer of skin forms a mantle over the visceral hump.

Unio (Fresh-water Mussels)

• It belongs to bivalve molluscs.
• The animal is sedentary and eventually settles down on the bottom of the river or the lake through the mud or sand.

Concept:

• The animal kingdom is divided into different phyla based on symmetry, level of organization, presence/absence of coelom, etc.
•  Kingdom Animalia is divided into 11 different phyla.

Explanation:

Let us see a few organisms and their phyla:

Sl. No	Organism	Commonly known as	Phylum	Image
1	Physalia	Portuguese man-of-war	It belongs to Phylum Cnidaria. The name comes from its resemblance to the warship, the Portuguese man-of-war. These animals are mostly aquatic and have cnidoblasts on their tentacles and body. Cnidoblast provides protection and helps in anchorage and capture of prey.
2	Limulus	King crab	It belongs to Phylum Arthropoda. It is a  marine arthropod. It has changed very little compared to its millions of years old ancestors hence, it is called a living fossil.
3	Ancylostoma	Hookworm	It belongs to Phylum Aschelminthes. The body of roundworms is circular in cross-section. They are mostly parasitic and live inside the body of the host.
4	Pinctada	Pearl oyster	It belongs to Phylum Mollusca. It is mostly marine. It makes a shell (from aragonite, and conchiolin)  around its body for protection.

So, the correct answer is option 4, a - ii, b - iii, c - iv, d - i.

Explanation:

• Option 1: Centipede, millipede, spider, scorpion-Insecta - INCORRECT

​Centipede:

• PHYLUM - Arthropoda [Thick chitinous cuticle as an exoskeleton and jointed appendages.]
• CLASS - Chilopoda [Hundred-legged with body divisible into head and trunk.]

Millipede:

• PHYLUM - Arthropoda [Thick chitinous cuticle as an exoskeleton and jointed appendages.]
• CLASS - Diplopoda [Thousand-legged with body divisible into a head, thorax, and abdomen.]

Spider:

• PHYLUM - Arthropoda [Thick chitinous cuticle as an exoskeleton and jointed appendages.]
• CLASS - Arachnida [Cephalothorax with six pairs of appendages.]

Scorpion:

• PHYLUM - Arthropoda [Thick chitinous cuticle as an exoskeleton and jointed appendages.]
• CLASS - Arachnida [Cephalothorax with six pairs of appendages.]​

​Option 2: House fly, butterfly, tsetse fly, silverfish-Insecta - CORRECT

​​​House fly:

• PHYLUM - Arthropoda [Thick chitinous cuticle as an exoskeleton and jointed appendages.]
• CLASS - Insecta [Head bears a pair of compound eyes, a pair of antennae, and mouth parts adapted for chewing, biting, piercing sucking, etc.]

Butterfly:

• PHYLUM - Arthropoda [Thick chitinous cuticle as an exoskeleton and jointed appendages.]
• CLASS - Insecta [Head bears a pair of compound eyes, a pair of antennae, and mouth parts adapted for chewing, biting, piercing, sucking, etc.]

Tsetse fly:

• PHYLUM - Arthropoda [Thick chitinous cuticle as an exoskeleton and jointed appendages.]
• CLASS - Insecta [Head bears a pair of compound eyes, a pair of antennae and mouth parts adapted for chewing, biting, piercing, sucking, etc.]

Silverfish:

• PHYLUM - Arthropoda [Thick chitinous cuticle as an exoskeleton and jointed appendages.]
• CLASS - Insecta [Head bears a pair of compound eyes, a pair of antennae, and mouth parts adapted for chewing, biting, piercing, sucking, etc.]

Option 3: Spiny anteater, sea urchin, sea cucumber- Echinodermata - INCORRECT

​​Spiny anteater:​

• ​PHYLUM - Chordata [Presence of dorsal tubular nerve cord, pharyngeal gill slits, and notochord at some stage of development.]
• SUB-PHYLUM - Vertebrata [ Presence of vertebral column]
• CLASS - Mammalia [Presence of mammary gland]

Sea urchin:

• ​PHYLUM - Echinodermata [Marine animal showing usually pentamerous radial symmetry with podia or tube feet projecting out of the body.]
• CLASS - Echinoidea [Body is spherical, disc-like, oval, or heart-shaped with an endoskeleton made up of closely fitted calcareous plates with movable spines.]

​Sea cucumber:​

• ​PHYLUM - Echinodermata [Marine animal showing usually pentamerous radial symmetry with podia or tube feet projecting out of the body.]
• ​CLASS - Holothuroidea [Endoskeleton is reduced to microscopic spicules or plates that are embedded in the body wall. Mouth surrounded by a set of tentacles.]

​​Option 4: Flying fish, cuttlefish, silverfish- Pisces - INCORRECT

​​Flying fish:​

• ​PHYLUM - Chordata [Presence of dorsal tubular nerve cord, pharyngeal gill slits, and notochord at some stage of development.]
• SUB-PHYLUM - Vertebrata [ Presence of vertebral column]
• SUPER CLASS - Pisces [Aquatic and bears fins]
• CLASS - Osteichthyes [Marine or freshwater fish with bony exoskeleton.

Cuttlefish:​

• ​PHYLUM - Mollusca [Body is soft, unsegmented and bilaterally symmetrical. The body consists of a head, foot, mantle, and visceral mass.]
• CLASS - Cephalopoda [Shell embedded in the mantle. The foot altered into a series of tentacles encircling the mouth.]

​​​Silverfish:​

• PHYLUM - Arthropoda [Thick chitinous cuticle as an exoskeleton and jointed appendages.]
• CLASS - Insecta [Head bears a pair of compound eyes, a pair of antennae and mouth parts adapted for chewing, biting, piercing, sucking,etc.]

So the correct answer is option 2 (House fly, butterfly, tsetse fly, silverfish- Insecta).

Explanation:

• Option 1: Centipede, millipede, spider, scorpion-Insecta - INCORRECT

​Centipede:

• PHYLUM - Arthropoda [Thick chitinous cuticle as an exoskeleton and jointed appendages.]
• CLASS - Chilopoda [Hundred-legged with body divisible into head and trunk.]

Millipede:

• PHYLUM - Arthropoda [Thick chitinous cuticle as an exoskeleton and jointed appendages.]
• CLASS - Diplopoda [Thousand-legged with body divisible into a head, thorax, and abdomen.]

Spider:

• PHYLUM - Arthropoda [Thick chitinous cuticle as an exoskeleton and jointed appendages.]
• CLASS - Arachnida [Cephalothorax with six pairs of appendages.]

Scorpion:

• PHYLUM - Arthropoda [Thick chitinous cuticle as an exoskeleton and jointed appendages.]
• CLASS - Arachnida [Cephalothorax with six pairs of appendages.]​

​Option 2: House fly, butterfly, tsetse fly, silverfish-Insecta - CORRECT

​​​House fly:

• PHYLUM - Arthropoda [Thick chitinous cuticle as an exoskeleton and jointed appendages.]
• CLASS - Insecta [Head bears a pair of compound eyes, a pair of antennae, and mouth parts adapted for chewing, biting, piercing sucking, etc.]

Butterfly:

• PHYLUM - Arthropoda [Thick chitinous cuticle as an exoskeleton and jointed appendages.]
• CLASS - Insecta [Head bears a pair of compound eyes, a pair of antennae, and mouth parts adapted for chewing, biting, piercing, sucking, etc.]

Tsetse fly:

• PHYLUM - Arthropoda [Thick chitinous cuticle as an exoskeleton and jointed appendages.]
• CLASS - Insecta [Head bears a pair of compound eyes, a pair of antennae and mouth parts adapted for chewing, biting, piercing, sucking, etc.]

Silverfish:

• PHYLUM - Arthropoda [Thick chitinous cuticle as an exoskeleton and jointed appendages.]
• CLASS - Insecta [Head bears a pair of compound eyes, a pair of antennae, and mouth parts adapted for chewing, biting, piercing, sucking, etc.]

Option 3: Spiny anteater, sea urchin, sea cucumber- Echinodermata - INCORRECT

​​Spiny anteater:​

• ​PHYLUM - Chordata [Presence of dorsal tubular nerve cord, pharyngeal gill slits, and notochord at some stage of development.]
• SUB-PHYLUM - Vertebrata [ Presence of vertebral column]
• CLASS - Mammalia [Presence of mammary gland]

Sea urchin:

• ​PHYLUM - Echinodermata [Marine animal showing usually pentamerous radial symmetry with podia or tube feet projecting out of the body.]
• CLASS - Echinoidea [Body is spherical, disc-like, oval, or heart-shaped with an endoskeleton made up of closely fitted calcareous plates with movable spines.]

​Sea cucumber:​

• ​PHYLUM - Echinodermata [Marine animal showing usually pentamerous radial symmetry with podia or tube feet projecting out of the body.]
• ​CLASS - Holothuroidea [Endoskeleton is reduced to microscopic spicules or plates that are embedded in the body wall. Mouth surrounded by a set of tentacles.]

​​Option 4: Flying fish, cuttlefish, silverfish- Pisces - INCORRECT

​​Flying fish:​

• ​PHYLUM - Chordata [Presence of dorsal tubular nerve cord, pharyngeal gill slits, and notochord at some stage of development.]
• SUB-PHYLUM - Vertebrata [ Presence of vertebral column]
• SUPER CLASS - Pisces [Aquatic and bears fins]
• CLASS - Osteichthyes [Marine or freshwater fish with bony exoskeleton.

Cuttlefish:​

• ​PHYLUM - Mollusca [Body is soft, unsegmented and bilaterally symmetrical. The body consists of a head, foot, mantle, and visceral mass.]
• CLASS - Cephalopoda [Shell embedded in the mantle. The foot altered into a series of tentacles encircling the mouth.]

​​​Silverfish:​

• PHYLUM - Arthropoda [Thick chitinous cuticle as an exoskeleton and jointed appendages.]
• CLASS - Insecta [Head bears a pair of compound eyes, a pair of antennae and mouth parts adapted for chewing, biting, piercing, sucking,etc.]

So the correct answer is option 2 (House fly, butterfly, tsetse fly, silverfish- Insecta).

The correct answer is They possess a closed circulatory system.

Explanation:

• Hemichordata was earlier considered as a sub-phylum under phylum Chordata. But now it is placed as a separate phylum under non-chordata.
• Hemichordates have a rudimentary structure in the collar region called stomochord, a structure similar to notochord.
• This phylum consists of a small group of worm-like marine animals with organ-system level of organisation.
• They are bilaterally symmetrical, triploblastic and coelomate animals.
• The body is cylindrical and is composed of an anterior proboscis, a collar and a long trunk (Figure 4.15).
• The circulatory system is of open type.
• Respiration takes place through gills.
• Excretory organ is proboscis gland. Sexes are separate.
• Fertilisation is external.
• Development is indirect.
• Examples: Balanoglossus and Saccoglossus.