Phylum-Arthropoda Questions in English

(A) Class-$Crustacea$ belongs to the sub-phylum-$Mandibulata$ of phylum-$Arthropoda$.
In crustaceans,the head is often fused with the thorax to form a $Cephalothorax$.
Respiration occurs through gills or the body surface.
Appendages in crustaceans are typically $biramous$ (branched).

(B) Arthropods possess an exoskeleton made of chitin,which is often reinforced with proteins or calcium carbonate.
This chitinous exoskeleton provides structural support,protection against desiccation,and serves as an attachment site for muscles.
The presence of this exoskeleton is a key evolutionary adaptation that favours the survival of arthropods in diverse environments,contributing to their status as the most successful and widely distributed phylum in the animal kingdom.

(D) Arthropods possess an open circulatory system and are true coelomates (schizocoelomates). Their body is segmented and typically divided into head,thorax,and abdomen. However,fertilization in arthropods is usually internal,not external. Therefore,the statement that fertilization is usually external is incorrect.

(A) $Arthro$ means jointed and $Poda$ means appendages.
Therefore,$Arthropoda$ have jointed appendages,which is the characteristic feature of all arthropods and gives the phylum its name.

(C) Statocysts are specialized sensory organs that function as organs of equilibrium or balance in many invertebrates,including arthropods and some mollusks.
They detect the orientation of the organism relative to gravity.

(D) . $A$ vector of disease: $Culex$ (mosquito) acts as a vector for pathogens causing diseases like filariasis.
$(b)$. $A$ gregarious pest: $Locusta$ (locust) is known for its gregarious behavior,causing massive damage to crops.
$(c)$. $A$ living fossil: $Limulus$ (king crab or horseshoe crab) is considered a living fossil because it has remained unchanged for millions of years.
$(d)$. An economically important insect: $Bombyx$ (silkworm) is economically important as it produces silk.

(A) The body of an insect is divided into three distinct regions:
$1$. Head: Contains sensory organs and mouthparts.
$2$. Thorax: The middle section,which bears the legs and wings.
$3$. Abdomen: The posterior section,which contains the digestive and reproductive organs.

(C) $Buthus$ (scorpions) are ovoviviparous animals. In these organisms,the eggs hatch within the female's body,and the female gives birth to live young ones instead of laying eggs.

(D) Paurometabolous development is a type of gradual metamorphosis where the young (nymphs) resemble the adults in their mode of life and habitat but differ in size and reproductive maturity.
$Periplaneta$ (Cockroach) exhibits this type of development.
In contrast,$Bombyx$ (silkworm) and $Anopheles$ (mosquito) undergo complete metamorphosis (holometabolous),while $Apis$ (honeybee) also undergoes complete metamorphosis.

(B) $Apis$ (honey bee) provides honey,which is used as food and medicine,and beeswax,which is used in paints and cosmetics.
$Bombyx$ (silkworm) provides silk,which is used for making shawls,sarees,and other garments.
$Laccifer$ (lac insect) provides lac,which acts as sealing wax and is used in making bangles,toys,etc.

(C) Option $C$ is the correct distinguishing feature of a butterfly. The differences between a butterfly and a moth are summarized below:

< strong>Butterfly	< strong>Moth
$i$. It is diurnal (active during the day).	$i$. It is nocturnal (active during the night).
$ii$. Body is slender and not robust.	$ii$. Body is often robust and stout.
$iii$. Antennae are long with a knobbed (globose) end.	$iii$. Antennae are short,tapering,or feathery.
$iv$. When at rest,it keeps its wings held together vertically on its back.	$iv$. When at rest,it keeps its wings held out horizontally.

(C) Assertion is true: The presence of a chitinous exoskeleton is a defining characteristic of the phylum $Arthropoda$.
Reason is false: The chitinous exoskeleton is impermeable to water. It serves as a protective covering that prevents desiccation (water loss) and does not allow the diffusion of water vapour from the atmosphere into the body or vice-versa.
Therefore,the Assertion is true but the Reason is false.

(C) In an open circulatory system,the blood pumped by the heart passes through large vessels into open spaces or body cavities called sinuses.
Arthropods,such as insects,and most molluscs possess an open circulatory system.
In contrast,fishes,earthworms (annelids),and birds possess a closed circulatory system,where blood remains confined within blood vessels.

(D) The family $Muscidae$ includes the common house fly.
$1$. The house fly,scientifically known as $Musca$ $domestica$,belongs to the family $Muscidae$ and the order $Diptera$.
$2$. Fire fly belongs to the family $Lampyridae$.
$3$. Grasshopper belongs to the family $Acrididae$.
$4$. Cockroach belongs to the family $Blattidae$.
Therefore,the correct option is $D$.

(N/A) $\rightarrow$ They are bilaterally symmetrical,triploblastic,segmented,and coelomate animals.
$\rightarrow$ The body of arthropods is covered by a chitinous exoskeleton.
$\rightarrow$ The body consists of head,thorax,and abdomen.
$\rightarrow$ They have jointed appendages (arthros = joint,poda = appendages).
$\rightarrow$ Respiratory organs include gills,book gills,book lungs,or the tracheal system.
$\rightarrow$ The circulatory system is of the open type.
$\rightarrow$ Sensory organs like antennae,eyes (compound and simple),and statocysts or balance organs are present.

(N/A) $\rightarrow$ Insects are considered the most successful group of animals due to several evolutionary advantages:
$1$. Exoskeleton: They possess a chitinous exoskeleton that provides protection,prevents desiccation,and supports their body.
$2$. High Reproductive Rate: They exhibit a high rate of reproduction,ensuring the survival of the species even under adverse conditions.
$3$. Diverse Feeding Habits: They have evolved specialized mouthparts adapted to various feeding habits,allowing them to exploit a wide range of food sources.
$4$. Adaptability: They have successfully survived numerous environmental changes and are adapted to diverse habitats,including terrestrial,aquatic,and aerial environments.

(B) $\rightarrow$ Location: Malpighian tubules and green glands (also known as antennary glands) are specialized structures found in the phylum $Arthropoda$.
$\rightarrow$ Function: These structures serve as the primary excretory organs in various arthropods. Malpighian tubules are typically found in insects,while green glands are found in crustaceans like prawns.

(B) The exoskeleton of arthropods is primarily composed of $Chitin$.
$Chitin$ is a long-chain polymer of $N$-acetylglucosamine,a derivative of glucose.
It provides structural support and protection to the arthropod body.
$Cellulose$ is found in plant cell walls,$Cutin$ is a waxy layer on plant surfaces,and $Glucosamine$ is a monomeric unit,not the structural polymer itself.

(C) In an $Open$ circulatory system,the blood is pumped out of the heart and the cells and tissues are directly bathed in it. The blood vessels are poorly developed or absent,and the blood flows into open spaces called sinuses or lacunae. This is commonly observed in arthropods and molluscs (except cephalopods).

(C) Malpighian tubules are the primary excretory organs found in the phylum $Arthropoda$,specifically in insects and many other terrestrial arthropods.
These tubules help in the removal of nitrogenous wastes from the body cavity (hemocoel) and empty them into the digestive tract.
Therefore,the correct option is $C$.

(D) Ecdysis,also known as moulting,is the process of shedding the old exoskeleton to allow for growth. This is a characteristic feature of the phylum $Arthropoda$,as their exoskeleton is made of chitin and does not grow with the body. Therefore,they must shed it periodically to increase in size.

(D) An open circulatory system is a characteristic feature of the phylum $Arthropoda$ and $Mollusca$ (except cephalopods).
Among the given options,the $Earthworm$ $(Annelida)$,$Leech$ $(Annelida)$,and $Sandworm$ $(Annelida)$ possess a closed circulatory system.
$Grasshopper$ belongs to the phylum $Arthropoda$,which is characterized by an open circulatory system where blood flows through body cavities called sinuses.

(C) The phylum $Arthropoda$ is the largest phylum in the animal kingdom.
It includes insects,spiders,crustaceans,and many other groups.
Approximately two-thirds of all named species on Earth are arthropods.
Therefore,it contains the largest number of animals.

(C) The phylum $Arthropoda$ is the largest phylum of $Animalia$ which includes insects.
These animals have an organ-system level of organization.
They are bilaterally symmetrical,triploblastic,segmented,and coelomate animals.
The body of arthropods is covered by a chitinous exoskeleton,which provides protection and support.

(C) The correct answer is $C$. Honey bees are not considered gregarious pests; they are beneficial insects that provide honey,wax,and pollination services. Gregarious pests are insects that live in large groups and cause significant damage to crops,such as the locust $(Locusta)$. Therefore,the statement 'Gregarious pest - Honey bee' is incorrect.

(C) The phylum $Arthropoda$ is the largest phylum in the animal kingdom.
Members of this phylum exhibit a high degree of cephalization and possess well-developed sensory organs.
These include antennae (for tactile and chemical sensing),compound or simple eyes (for vision),and statocysts (for balance and orientation).
These specialized structures allow arthropods to interact effectively with their environment.

(A) The exoskeleton of arthropods is made up of $Chitin$.
$Chitin$ is a complex polysaccharide,specifically a nitrogen-containing polysaccharide known as $N-acetylglucosamine$ polymer.
It provides structural support and protection to the organisms belonging to the phylum $Arthropoda$.

(A) The correct matching is as follows:
$P$. Coleoptera: These are commonly known as beetles.
$Q$. Lepidoptera: This order includes insects like the tobacco budworm and armyworm.
$R$. Diptera: This order includes flies and mosquitoes.
Therefore, the correct sequence is $(P-I), (Q-III), (R-II)$.

(A) The phylum $Arthropoda$ is the largest phylum in the animal kingdom. It includes insects,spiders,crustaceans,and centipedes. Approximately two-thirds of all named species on Earth are arthropods. This high diversity is attributed to their versatile exoskeleton,segmented body,and jointed appendages,which allow them to adapt to various environments.

(C) living fossil is an extant taxon that closely resembles related species known only from the fossil record.
$Limulus$,commonly known as the King Crab,belongs to the phylum $Arthropoda$ and class $Merostomata$.
It has remained virtually unchanged for millions of years,making it a classic example of a living fossil.
$Spongilla$ is a freshwater sponge,$Obelia$ is a cnidarian,and $Aplysia$ is a sea hare (mollusk),none of which are classified as living fossils.

(C) The features described are characteristic of the phylum $Arthropoda$.
$1$. It is the largest phylum of $Animalia$ which includes insects.
$2$. They have jointed appendages ($Arthro$ = joint,$poda$ = appendages).
$3$. Their body is covered by a chitinous exoskeleton.
$4$. They are mostly dioecious (sexes are separate).
Among the given options,$Apis$ (honey bee) belongs to the phylum $Arthropoda$.
$Pheretima$ belongs to $Annelida$,$Fasciola$ belongs to $Platyhelminthes$,and $Ascaris$ belongs to $Aschelminthes$.

(B) In aquatic arthropods (such as crustaceans) and molluscs,the respiratory organs are specialized structures known as gills or branchiae.
These structures are highly vascularized and are adapted for the exchange of dissolved oxygen from the water into the blood and the removal of carbon dioxide from the blood into the water.
Therefore,gills are the primary respiratory organs for most aquatic members of these phyla.

(C) $1$. Phylum $Arthropoda$ is the largest phylum of $Animalia$ which includes insects,arachnids,crustaceans,and myriapods,not just insects. So,option $A$ is incorrect.
$2$. $Arthropods$ are triploblastic,bilaterally symmetrical,and coelomate,but they are distinctly segmented (metamerically segmented). So,option $B$ is incorrect.
$3$. $Arthropods$ possess various sensory organs such as antennae,simple eyes,and compound eyes,which help them interact with their environment. So,option $C$ is correct.
$4$. Development in $Arthropoda$ can be direct or indirect (involving larval stages). Therefore,saying they 'always' show indirect development is incorrect. So,option $D$ is incorrect.

(C) 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.
They are characterized by jointed appendages and a chitinous exoskeleton.

(B) To determine the correct group,we analyze the phylum of each organism:
$A$. Earthworm (Annelida),Filarial worm (Aschelminthes),Tapeworm (Platyhelminthes). These belong to different phyla.
$B$. Prawn (Arthropoda),Scorpion (Arthropoda),Locusta (Arthropoda). All these organisms belong to the phylum Arthropoda.
$C$. Sponge (Porifera),Sea-anemone (Cnidaria),Starfish (Echinodermata). These belong to different phyla.
$D$. Malarial parasite (Protozoa),Amoeba (Protozoa),Mosquito (Arthropoda). These belong to different phyla.
Therefore,the group that belongs to the same phylum is Prawn,Scorpion,and Locusta.

(A) The phylum $Arthropoda$ is characterized by the presence of an external skeleton known as the exoskeleton.
This exoskeleton is composed of $chitin$,a tough,protective polysaccharide.
This structure provides support,protection,and prevents desiccation in these organisms.
Therefore,the correct option is $A$.

(A) is the correct answer.
Butterflies and moths both belong to the order $Lepidoptera$.
Butterflies typically possess long,thin antennae that end in a club-like shape,whereas moths generally have feathery or comb-like antennae.
Both insects possess two pairs of wings.
Generally,moths are nocturnal (active at night),while butterflies are diurnal (active during the day).
Both groups possess compound eyes,though their visual structures can vary in complexity.

(B) The correct answer is $B$.
Arthropods possess an exoskeleton that provides structural support and protection.
This exoskeleton is composed of $Chitin$,which is a complex polysaccharide.
$Chitin$ is a polymer of $N$-acetylglucosamine units linked by $\beta-1,4$-glycosidic bonds.