Phylum-Arthropoda Questions in English

(A) Centipedes (class Chilopoda) and millipedes (class Diplopoda) belong to the subphylum Myriapoda within the phylum Arthropoda. The term 'Myriapoda' refers to organisms with many legs. Therefore,they are members of the group Myriapoda.

(D) Insects belong to the phylum $Arthropoda$,class $Insecta$. The most diagnostic feature of insects is the presence of three pairs of jointed legs (total $6$ legs) attached to the thorax. While wings,antennae,and compound eyes are common in many insects,they are not exclusive to them (e.g.,some arachnids have compound eyes,and many other arthropods have antennae). Therefore,the presence of jointed appendages (specifically $3$ pairs of legs) is the defining characteristic.

(A) Green glands,also known as antennary glands,are specialized excretory organs found in certain crustaceans,such as prawns (crustaceans are a class of arthropods).
These glands function primarily in the process of excretion by filtering metabolic waste from the hemolymph and excreting it from the body.
Therefore,the correct function is excretion.

(C) The class $Arachnida$ (which includes spiders,scorpions,ticks,and mites) is a group of arthropods characterized by specific morphological features.
$1$. The body is divided into two main regions: the cephalothorax and the abdomen.
$2$. They possess four pairs of walking legs (total $8$ legs) attached to the cephalothorax.
$3$. They lack antennae and wings,which distinguishes them from the class $Insecta$ (which has three pairs of legs and antennae).
Therefore,the presence of four pairs of legs is the most diagnostic feature for identifying members of the class $Arachnida$.

(A) The gregarious pest refers to an insect that lives in large groups and causes significant damage to crops.
Locusta (Locust) is a well-known gregarious pest belonging to the phylum Arthropoda and class Insecta.
It is famous for its swarming behavior,which can destroy vast areas of vegetation.
Culex and Aedes are mosquitoes (vectors),and Apis is the honey bee (beneficial insect).

(B) An open circulatory system is a type of circulatory system where the blood is not confined to blood vessels but flows into body cavities called sinuses or hemocoels.
This type of system is characteristic of phylum $Arthropoda$ (e.g.,insects,spiders,crustaceans) and most mollusks.
In contrast,fishes,amphibians,and earthworms possess a closed circulatory system where blood flows through a network of vessels.

(D) An open circulatory system is a type of circulatory system where the blood is pumped out of the heart into body cavities (sinuses) called hemocoel,where tissues and organs are bathed in blood.
This type of system is characteristic of Arthropods (e.g.,insects,crustaceans) and most Mollusks.
Annelids (except leeches) and Chordates possess a closed circulatory system,where blood flows through a series of vessels of varying diameters (arteries,veins,and capillaries).
Therefore,the open circulatory system is found in Arthropoda (labeled as $1$).
Thus,the correct option is $D$ (Only $a$).

(B) The class $Insecta$ (or $Insecta$ under the phylum $Arthropoda$) is characterized by several features.
However,the most defining and universal characteristic of the phylum $Arthropoda$,which includes $Insecta$,is the presence of a hard,protective $Chitinous$ $exoskeleton$.
This exoskeleton provides structural support,protection,and prevents desiccation.
While jointed appendages and compound eyes are also features of arthropods,the $Chitinous$ $exoskeleton$ is the primary diagnostic feature.

(C) The defining characteristic of the class $Insecta$ (phylum $Arthropoda$) is the presence of three pairs of jointed legs (total $6$ legs) on the thorax region of the body.
While segmented bodies,chitinous exoskeletons,and compound eyes are also features of many arthropods,the presence of three pairs of legs is the specific diagnostic feature used to identify an insect.

(D) The eggs of insects such as butterflies,moths,bees,and beetles are classified as $Centrolecithal$ eggs.
In $Centrolecithal$ eggs,the yolk is concentrated in the center of the egg,while the cytoplasm is restricted to the peripheral layer.
This type of egg is characteristic of most arthropods,including insects.

(C) Peripatus is considered a connecting link between the phyla $Annelida$ and $Arthropoda$. It exhibits characteristics of both groups: it possesses segmented bodies and nephridia,which are typical of $Annelida$,and it also has a tracheal system and open circulatory system,which are characteristic of $Arthropoda$.

(D) Peripatus is a genus of velvet worms in the phylum Onychophora. It exhibits characteristics of both $Annelida$ (such as a segmented body,thin cuticle,and segmentally arranged nephridia) and $Arthropoda$ (such as a tracheal system for respiration,open circulatory system,and jointed appendages). Therefore,it is considered a connecting link between $Annelida$ and $Arthropoda$.

(D) Acarology is a branch of zoology that specifically focuses on the study of mites and ticks,which belong to the subclass $Acari$ within the class $Arachnida$. It is a specialized field of entomology and arachnology.

(D) $Culex$ $fatigans$ (now commonly referred to as $Culex$ $quinquefasciatus$) is a species of mosquito. It acts as a primary vector for the transmission of $Wuchereria$ $bancrofti$,the filarial worm that causes lymphatic filariasis (elephantiasis) in humans.

(D) $Culex$ $fatigans$ (also known as $Culex$ $quinquefasciatus$) is a species of mosquito. It is a primary vector for the transmission of $Wuchereria$ $bancrofti$,the parasite responsible for filariasis (elephantiasis) in humans. Therefore,it is classified as an insect belonging to the order Diptera.

(A) In organisms with an open circulatory system,such as many arthropods and mollusks,blood is pumped into body cavities called sinuses or hemocoels.
Because the blood is not confined within a continuous network of vessels,it flows at a low pressure.
Furthermore,the flow is irregular because it is not driven by the high-pressure,rhythmic contractions of a closed vascular system,but rather by the movement of the body and the heart's pumping into open spaces.
Therefore,the blood pressure in blood sinuses is low and irregular.

(D) In $Arthropoda$,the circulatory system is of the open type. In an open circulatory system,blood is pumped by the heart into blood vessels that open into body cavities (sinuses or haemocoel). Because the blood is not confined to a closed network of vessels,the blood pressure is low and irregular.

(B) closed circulatory system is one where blood flows through a series of vessels (arteries,veins,and capillaries).
$1$. Annelids (like earthworms) possess a closed circulatory system.
$2$. Arthropods possess an open circulatory system,where blood (hemolymph) flows into body cavities called sinuses.
$3$. Cephalopods (a class of mollusks) are an exception in the phylum Mollusca as they possess a closed circulatory system.
$4$. Vertebrates possess a closed circulatory system.
Therefore,the correct answer is Arthropods.

(C) Arthropods possess an open circulatory system. In an open circulatory system,the blood (hemolymph) is not confined to vessels but flows through body cavities called sinuses or hemocoel. Because the blood is not pumped through a closed network of high-pressure vessels,the blood pressure is generally low and irregular compared to closed circulatory systems found in vertebrates or some mollusks like cephalopods.

(D) The provided figure illustrates the circulatory system of an arthropod (specifically an insect).
In this system,the heart acts as a $Pump$ $(A)$ to circulate the haemolymph.
The body cavity filled with haemolymph is known as the $Haemocoel$.
However,looking at the specific labels in the diagram,$A$ points to the heart/pump structure,and $B$ points to the opening or ostia through which haemolymph enters the heart.
Therefore,$A$ represents the $Pump$ and $B$ represents the $Ostia$.

(C) In an open circulatory system,the blood is pumped out of the heart into body cavities called sinuses or lacunae,rather than being confined within vessels.
This system is characterized by poorly developed arteries and veins.
Among the given options,the phylum $Arthropoda$ (which includes insects,spiders,and crustaceans) is well-known for possessing an open circulatory system.
$Coelenterata$ and $Platyhelminthes$ lack a circulatory system entirely,while $Porifera$ rely on a water transport system.

(B) Bilateral symmetry is a body plan where the organism can be divided into two identical left and right halves along a single plane.
$1$. $Porifera$ (sponges) are mostly asymmetrical.
$2$. $Cnidaria$ (coelenterates) exhibit radial symmetry.
$3$. $Echinodermata$ adults exhibit radial symmetry (pentamerous),although their larvae are bilaterally symmetrical.
$4$. $Arthropoda$ are triploblastic,coelomate animals that exhibit bilateral symmetry.

(C) The phylum $Arthropoda$ is the largest phylum in the animal kingdom.
It includes insects,arachnids,myriapods,and crustaceans.
Approximately two-thirds of all named species on Earth are arthropods,making it the most diverse and numerous group in terms of species count.

(A) The phylum $Arthropoda$ is characterized by the presence of jointed appendages. The term '$Arthropoda$' is derived from the Greek words '$arthros$' meaning 'joint' and '$podos$' meaning 'foot'. These organisms also possess a chitinous exoskeleton and a segmented body.

(C) Arthropoda is the largest phylum in the animal kingdom.
It includes insects,arachnids,myriapods,and crustaceans.
According to biological data,over two-thirds $(2/3)$ of all named species on Earth are arthropods.
Therefore,the correct proportion is $2/3$.

(D) The phylum $Arthropoda$ is the largest phylum of $Animalia$ which includes insects.
Their body is covered by a tough,protective outer covering known as the exoskeleton.
This exoskeleton is composed of a polysaccharide called $Chitin$.
$Chitin$ provides structural support and protection to the organism while allowing for movement through jointed appendages.

(C) In the phylum $Arthropoda$,the body is covered by a hard,chitinous exoskeleton.
Since this exoskeleton does not grow along with the animal,it must be shed periodically to allow for growth.
This process of shedding the old exoskeleton is technically known as $Ecdysis$ or molting.
$Metamorphosis$ refers to the transformation from an immature form to an adult form,while $Metamerism$ refers to the segmentation of the body.

(D) The term $Cephalothorax$ is derived from the Greek words $kephale$ (head) and $thorax$ (chest).
It refers to a fused body region found in many arthropods,such as crustaceans and arachnids,where the head and the thorax are joined together to form a single functional unit.
Therefore,the correct option is $D$.

(A) book lung is a type of respiratory organ found in many arachnids,such as spiders and scorpions,which belong to the phylum $Arthropoda$.
It consists of a series of thin,leaf-like air pockets (lamellae) arranged like the pages of a book,which increase the surface area for gas exchange.
Therefore,it is a respiratory organ of $Arthropoda$.

(B) The phylum $Arthropoda$ is the largest phylum of $Animalia$,which includes insects.
Over two-thirds of all named species on earth are arthropods.
They exhibit a wide range of reproductive strategies,including both oviparous (egg-laying) and ovoviviparous (eggs hatch inside the mother's body) species.
Therefore,the correct option is $B$.

(A) Parthenogenesis is a form of asexual reproduction where an embryo develops from an unfertilized egg. Among the given options,the phylum $Arthropoda$ is well-known for exhibiting parthenogenesis in various species,such as honey bees ($Apis$ $mellifera$),aphids,and certain wasps. In honey bees,unfertilized eggs develop into male drones.

(C) $1$. $S$ (Statement) is true: Malpighian tubules are indeed the primary excretory organs in insects and many other $Arthropods$.
$2$. $R$ (Reason) is false: $Arthropoda$ is a separate phylum from $Mollusca$. $Arthropoda$ is the largest phylum in the animal kingdom,characterized by jointed appendages and a chitinous exoskeleton,whereas $Mollusca$ is the second-largest phylum,characterized by a soft body often protected by a calcareous shell.
$3$. Since $S$ is true and $R$ is false,the correct option is $C$.

(D) The phylum $Arthropoda$ is characterized by the presence of jointed appendages,a segmented body,and an exoskeleton made of chitin.
They possess an open circulatory system,meaning the blood flows through body cavities (hemocoel) rather than being confined within blood vessels.
Therefore,a closed circulatory system is $NOT$ a characteristic of $Arthropoda$.

(A) The phylum $Arthropoda$ is characterized by the following features:
$1$. They have a segmented body (divided into head,thorax,and abdomen).
$2$. They possess jointed appendages.
$3$. They have compound or simple eyes.
$4$. They have an open circulatory system and a true coelom (hemocoel).
$5$. Excretion occurs through Malpighian tubules or green glands,not nephridia (nephridia are typical of $Annelida$).
However,among the given options,option $A$ is the closest description of arthropod features,although 'nephridia' is technically incorrect for arthropods (it should be Malpighian tubules). Given the context of typical biology questions,option $A$ is the intended answer as it lists segmented body and compound eyes.

(D) The organisms $Sandfly$ (Insecta),$Scorpion$ (Arachnida),$Cockroach$ (Insecta),and $Silverfish$ (Insecta) all belong to the phylum $Arthropoda$.
Key characteristics of the phylum $Arthropoda$ include:
$1$. They possess jointed appendages ($Arthro$ = jointed,$poda$ = feet).
$2$. They have a dorsal heart.
$3$. They have an open circulatory system.
Since all these organisms are members of the phylum $Arthropoda$,they share these common features. Therefore,options $A$,$C$,and $D$ are technically correct descriptions of these organisms. However,in standard biological classification questions of this type,the presence of jointed appendages is the defining characteristic of the phylum $Arthropoda$.

(B) The phylum $Arthropoda$ is the largest phylum of the animal kingdom.
It includes insects and other related organisms.
Over two-thirds of all named species on earth are arthropods.

(C) Ecdysis,or moulting,is the process of shedding the old exoskeleton to allow for growth. This is a characteristic feature of the phylum $Arthropoda$,where the chitinous exoskeleton must be shed periodically because it does not grow with the animal. While some other groups like $Nematoda$ (Aschelminthes) also undergo moulting,$Arthropoda$ is the most prominent phylum associated with this process in the context of biological classification.

(A) Parthenogenesis is a form of asexual reproduction where an embryo develops from an unfertilized egg.
In the phylum $Arthropoda$,specifically in insects like honeybees ($Apis$ $mellifera$),aphids,and some wasps,parthenogenesis is a well-documented phenomenon.
For example,in honeybees,unfertilized eggs develop into male drones,while fertilized eggs develop into females (queens or workers).
Therefore,$Arthropoda$ is the correct phylum among the given options that exhibits parthenogenesis.

(A) Insects are characterized by the presence of jointed appendages and a chitinous exoskeleton. These features are the defining characteristics of the phylum $Arthropoda$. Therefore,insects belong to the phylum $Arthropoda$.

(C) Crab,scorpion,centipede,and prawn all belong to the phylum $Arthropoda$.
Key characteristics of the phylum $Arthropoda$ include:
$1$. They possess jointed appendages ($Arthro$ = joint,$poda$ = foot).
$2$. Their body is covered by a tough,chitinous exoskeleton.
$3$. They have a segmented body.
$4$. They possess an open circulatory system.
Option $A$ is incorrect because three pairs of legs are characteristic of $Insecta$,not all arthropods.
Option $B$ is incorrect because not all arthropods have two pairs of antennae (e.g.,insects have one pair).
Option $D$ is incorrect because not all arthropods have a cephalothorax or a tracheal system (e.g.,crustaceans use gills).
Therefore,the most common feature among these is the presence of jointed appendages and a chitinous exoskeleton.

(D) The organisms mentioned are: sandfly (insect),scorpion (arachnid),cockroach (insect),and silverfish (insect).
All these organisms belong to the phylum $Arthropoda$.
The defining characteristic of the phylum $Arthropoda$ is the presence of jointed appendages ($arthros$ = joint,$poda$ = foot).
Therefore,the correct statement is that they all possess jointed appendages.

(C) Let us analyze the options:
$A$: Tapeworm and Flatworm belong to Platyhelminthes,but Roundworm belongs to Aschelminthes. Thus,this group is incorrect.
$B$: Cuttlefish is a Mollusc,Silverfish is an Arthropod,and Starfish is an Echinoderm. None of these are Coelenterates. Thus,this group is incorrect.
$C$: Centipede,Millipede,and Silverfish all belong to the phylum Arthropoda. Thus,this group is correct.
$D$: Since option $C$ is correct,this is not the answer.

(C) The $statocyst$ (also known as an $otocyst$) is a sensory organ found in many aquatic invertebrates,including various arthropods like crustaceans (e.g.,crayfish,crabs).
Its primary function is to detect gravity and maintain balance or orientation in the water column.
Therefore,the $statocyst$ acts as a balancing organ.

(B) Ecdysis,also known as molting,is the process of shedding the old exoskeleton in arthropods.
Since the exoskeleton is rigid and does not grow with the animal,arthropods must periodically shed it to allow for growth and development.
This process involves the secretion of a new,larger exoskeleton underneath the old one before the old one is cast off.

(D) In the phylum $Arthropoda$,respiration occurs through various specialized organs depending on the habitat and species.
Common respiratory organs include $Gills$ (in aquatic forms),$Book$ $gills$,$Book$ $lungs$,and the $Tracheal$ $system$ (in terrestrial insects).
$Lungs$ (as found in vertebrates) are not present in $Arthropods$.
Therefore,the correct option is $D$.

(C) The phylum $Arthropoda$ is the first group in the animal kingdom to exhibit well-developed and distinct respiratory organs.
These include structures such as gills,book gills,book lungs,or the tracheal system,which are specialized for gas exchange in diverse environments.
While lower phyla like $Annelida$ rely on cutaneous respiration (skin) and $Mollusca$ have gills,$Arthropoda$ represents the first major evolutionary step toward complex,specialized respiratory systems adapted for both aquatic and terrestrial life.

(A) Compound eyes are a characteristic feature of the phylum $Arthropoda$.
These eyes consist of thousands of individual photoreceptor units called $ommatidia$.
They are highly efficient in detecting motion and are found in insects,crustaceans,and other arthropods.

(D) Green glands,also known as antennal glands,are excretory organs found in certain crustaceans,which belong to the phylum $Arthropoda$. These glands are responsible for the filtration and excretion of nitrogenous waste products in organisms like prawns and crayfish.

(B) In many arthropods, particularly in crustaceans and arachnids, the head and thorax segments are fused together to form a single functional unit known as the $Cephalothorax$. This structure is covered by a hard exoskeleton called the carapace.

(C) In an open circulatory system,the blood is pumped out of the heart into blood sinuses (spaces) rather than closed vessels.
Arthropods (like $Cockroach$ and $Silverfish$) and most mollusks possess an open circulatory system.
Leeches and earthworms (Annelids),humans and chimpanzees (Mammals),and frogs and fish (Vertebrates) possess a closed circulatory system where blood flows through a network of vessels.