Anatomy of Earthworm Questions in English

(A) In earthworms,nephridia are classified based on their location:
$1$. Septal nephridia $(P)$ are present on both sides of the intersegmental septa of segment $15$ to the last,which open into the intestine $(P-I)$.
$2$. Integumentary nephridia $(Q)$ are attached to the lining of the body wall of segment $3$ to the last,which open on the body surface $(Q-III)$.
$3$. Pharyngeal nephridia $(R)$ are present as three paired tufts in the $4^{th}, 5^{th}$ and $6^{th}$ segments $(R-II)$.
Therefore,the correct matching is $P-I, Q-III, R-II$.

(C) In earthworms,nephridia are the primary excretory organs.
$1$. Nephridia are segmentally arranged coiled tubules.
$2$. They perform the function of osmoregulation and excretion,thereby regulating the volume and composition of body fluids.
$3$. Based on their location,they are classified into three types: septal,integumentary,and pharyngeal.
$4$. They discharge waste materials either directly to the exterior or into the digestive tract.
$5$. Option $C$ is incorrect because nephridia are not just part of the digestive system; they are independent excretory organs that function throughout the body segments to maintain homeostasis.

(C) In earthworms,nephridia are classified based on their location and the way they discharge waste:
$1$. Septal nephridia $(P)$ are present on both sides of the intersegmental septa of segment $15$ to the last. They discharge their waste into the intestine,hence they are enteronephric $(I)$.
$2$. Integumentary nephridia $(Q)$ are attached to the lining of the body wall of segment $3$ to the last. They discharge their waste directly to the exterior,hence they are exonephric $(II)$.
$3$. Pharyngeal nephridia $(R)$ are present as three paired tufts in segments $4, 5,$ and $6$. They discharge their waste into the alimentary canal,hence they are enteronephric $(I)$.
Therefore,the correct matching is: $P-I, Q-II, R-I$.

(A) In the earthworm ($Pheretima$ $posthuma$),the nephridia are classified based on their location:
$1$. $P$ represents Pharyngeal nephridia,which are present as three paired tufts in the $4^{th}, 5^{th},$ and $6^{th}$ segments.
$2$. $Q$ represents Integumentary nephridia,which are attached to the lining of the body wall of segment $3$ to the last segment.
$3$. $R$ represents Septal nephridia,which are present on both sides of the intersegmental septa of segment $15$ to the last segment.
Therefore,the correct identification is $P=$ Pharyngeal nephridia,$Q=$ Integumentary nephridia,and $R=$ Septal nephridia.

(B) In the earthworm $(Pheretima)$,the nervous system is represented by ganglia arranged segmentally on the double ventral nerve cord. The anterior end (third and fourth segments) has the nerve cord bifurcating and encircling the pharynx to join the cerebral ganglia dorsally,forming a nerve ring. The cerebral ganglia,along with other nerves in the ring,integrate sensory inputs and command muscular responses. Option $B$ is incorrect because the nerve cord in earthworms is ventral,not dorsal.

(C) In earthworms (Pheretima):
$1$. Testes $(P)$ are located in the $10^{th}$ and $11^{th}$ segments $(V)$.
$2$. Accessory glands $(Q)$ are present in the $17^{th}$ and $19^{th}$ segments $(II)$.
$3$. The male genital pore $(R)$ is situated in the $18^{th}$ segment $(I)$.
$4$. Spermathecae $(S)$ are located in the $6^{th}$ to $9^{th}$ segments $(III)$.
$5$. Ovaries $(T)$ are located in the $13^{th}$ segment $(IV)$.
Therefore,the correct matching is $(P-V), (Q-II), (R-I), (S-III), (T-IV)$.

(D) In earthworms,fertilization and development occur within cocoons which are deposited in the soil.
Each cocoon contains several embryos,but only a few develop into young earthworms.
Typically,$2-22$ baby earthworms emerge from a single cocoon after a developmental period of about $3$ weeks.

(B) In the earthworm ($Pheretima$ $posthuma$),the glandular cells of the clitellum are responsible for the formation of the cocoon.
The clitellum is a prominent dark band of glandular and non-glandular tissue present in segments $14, 15,$ and $16$.
These segments secrete mucus and albumin,which harden to form the cocoon (or ootheca) that protects the developing embryos.

(A) In earthworms,the spermathecae are the organs responsible for storing the sperms received from another earthworm during the process of copulation.
There are four pairs of spermathecae located in the $6^{th}$ to $9^{th}$ segments.
Seminal vesicles are involved in the maturation and storage of the earthworm's own sperms,not the partner's sperms.
Therefore,the correct answer is Spermathecae.

(C) In an earthworm ($Pheretima$ $posthuma$),the female genital pore is a single,median aperture located on the ventral surface of the $14^{th}$ segment.
Its primary function is to release mature ova (eggs) from the ovaries into the cocoon during the process of reproduction.
Therefore,the correct function is the release of ova.

(C) In the reproductive system of the earthworm ($Pheretima$ $posthuma$):
$P$ represents the Spermathecae,which are four pairs of small sacs located in segments $6-9$.
$Q$ represents the Testis sacs,which are two pairs of sacs located in segments $10$ and $11$.
$R$ represents the Vas deferens,which are long ducts that run through segments $12-18$ and carry sperm to the male genital pores.

(D) The image shows the reproductive system of an earthworm ($Pheretima$ $posthuma$).
Earthworms are organisms that possess both male and female reproductive organs in the same individual.
Such organisms are termed as monoecious,bisexual,or hermaphrodite.
Therefore,all these terms are synonymous and correctly describe the organism shown.