Morphology of Earthworm Practice Questions
40 free Morphology of Earthworm practice questions for the NCERT Biology. Tap an option to answer — you get instant feedback, the correct answer, and a detailed explanation for every question.
The common Indian earthworms are Pheretima and:
- A Periplaneta
- B Lumbricus
- C Hirudinaria
- D Rana
Correct answer: Lumbricus
Pheretima and Lumbricus are the two most common genera of earthworms found in India. They belong to the phylum Annelida and are known for their role in soil fertility.
In earthworms, the dorsal surface of the body is marked by a dark median mid-dorsal line which represents the:
- A Ventral main nerve cord
- B Dorsal blood vessel
- C Alimentary canal
- D Clitellum
Correct answer: Dorsal blood vessel
The dorsal blood vessel is visible through the thin, moist skin as a dark median line on the dorsal side. The ventral surface is distinguished by the presence of genital openings.
The first segment of the earthworm, which contains the mouth, is called the:
- A The prostomium
- B Peristomium
- C Clitellum
- D Pygidium
Correct answer: Peristomium
The peristomium (buccal segment) is the true first segment of the earthworm and bears the mouth. The prostomium is a fleshy lobe that hangs over the mouth but is not a segment.
What is the primary function of the prostomium in an earthworm?
- A Digestion and nutrient absorption
- B Gaseous exchange across the skin
- C Burrowing and sensory detection
- D Excretion of nitrogenous waste
Correct answer: Burrowing and sensory detection
The prostomium acts as a wedge to force open cracks in the soil through which the earthworm may crawl. It also serves a sensory function, helping the worm perceive its environment.
In a mature earthworm, segments 14, 15, and 16 are covered by a prominent dark band of glandular tissue called the:
- A Prostomium
- B Metamere
- C Clitellum
- D Setae
Correct answer: Clitellum
The clitellum is a glandular thickening of the body wall in segments 14-16. It plays a vital role in reproduction by secreting the cocoon.
Four pairs of spermathecal apertures are situated on the ventro-lateral sides of the intersegmental grooves in which segments?
- A 5th - 9th
- B 14th - 16th
- C 17th - 19th
- D 1st - 4th
Correct answer: 5th - 9th
Spermathecal apertures are found in the intersegmental grooves of 5/6, 6/7, 7/8, and 8/9. These openings receive and store spermatozoa during copulation.
A single female genital pore is present in the mid-ventral line of segment:
- A 14th
- B 16th
- C 18th
- D 19th
Correct answer: 14th
The female genital pore is located mid-ventrally on the 14th segment, within the clitellar region. Male genital pores are found on the 18th segment.
S-shaped setae, embedded in the epidermal pits, are absent in which segments of the earthworm?
- A All segments have setae
- B First, last, and clitellum
- C Only the clitellar segments
- D Only the first and last segments
Correct answer: First, last, and clitellum
Setae are used for locomotion and are found in every segment except the first, the last, and the clitellum. They can be extended or retracted by specialized muscles.
The body wall of the earthworm is covered externally by a very thin non-cellular layer called:
- A Epidermis
- B Cuticle
- C Dermis
- D Mesoderm
Correct answer: Cuticle
The outermost layer is a thin, transparent, non-cellular cuticle. Below this lies the epidermis, followed by two layers of muscle (circular and longitudinal) and an innermost coelomic epithelium.
The alimentary canal of the earthworm is a straight tube. In which segments is the gizzard located?
- A 1st - 3rd
- B 5th - 7th
- C 8th - 9th
- D 15th - 26th
Correct answer: 8th - 9th
The gizzard is located in segments 8-9. It is a muscular structure that helps in grinding soil particles and decaying leaves (organic matter).
Calciferous glands, which neutralize the humic acid present in humus, are found in the:
- A Pharynx
- B Stomach
- C Intestine
- D Esophagus
Correct answer: Stomach
Calciferous glands are located in the stomach (segments 9-14). They secrete calcium carbonate to neutralize the acidity of the soil ingested by the worm.
Which internal feature of the earthworm intestine increases the effective area of absorption?
- A Gizzard
- B Typhlosole
- C Intestinal caeca
- D Lymph glands
Correct answer: Typhlosole
The typhlosole is an internal median fold of the dorsal wall of the intestine, typically found after the 26th segment (except the last 23-25 segments). It significantly increases the surface area for nutrient absorption.
Earthworms possess a closed circulatory system. Blood glands, which produce blood cells and hemoglobin, are present in which segments?
- A 4th, 5th, and 6th
- B 10th, 11th, and 12th
- C 15th, 16th, and 17th
- D Last 10 segments
Correct answer: 4th, 5th, and 6th
Blood glands are situated in segments 4, 5, and 6. They produce hemoglobin, which is dissolved in the blood plasma, and phagocytic blood cells.
Excretion and osmoregulation in earthworms are performed by tube-like coiled structures called:
- A Flame cells
- B Malpighian tubules
- C The nephridia
- D Statocysts
Correct answer: The nephridia
Nephridia are the excretory organs of the earthworm. There are three types based on location: septal, integumentary, and pharyngeal nephridia.
Which type of nephridia open into the intestine (enteronephric)?
- A Integumentary nephridia only
- B Septal and pharyngeal nephridia
- C Only the integumentary nephridia
- D Septal nephridia only
Correct answer: Septal and pharyngeal nephridia
Septal and pharyngeal nephridia are enteronephric, meaning they discharge waste into the alimentary canal. Integumentary nephridia are ectonephric and discharge waste directly to the exterior.
The nervous system of the earthworm is represented by ganglia arranged segmentally on the:
- A Dorsal solid nerve cord
- B Ventral hollow and single nerve cord
- C Ventral solid paired nerve cord
- D Dorsal hollow nerve cord
Correct answer: Ventral solid paired nerve cord
The nerve cord in earthworms is ventral, paired, and solid. It bears segmental ganglia that coordinate the activities of the segments.
Earthworms are hermaphrodites, but self-fertilization does not occur. Why?
- A Male and female organs are in different segments
- B They are protandrous — sperm matures before eggs
- C They lack functional copulatory organs
- D The genital pores are seasonally blocked
Correct answer: They are protandrous — sperm matures before eggs
Earthworms are protandrous, meaning the testes mature earlier than the ovaries. This ensures cross-fertilization during copulation.
Two pairs of testes are present in segments:
- A Inside the spermathecae
- B Inside the uterus
- C Inside secreted cocoons
- D Directly in the soil
Correct answer: Inside secreted cocoons
The clitellum secretes a cocoon into which eggs and stored sperm are deposited. Fertilization and subsequent development of the embryos into juvenile worms take place within this cocoon, which is left in the soil.
Fertilization and embryo development in earthworms occur inside:
- A The spermathecae
- B The uterus
- C Cocoons
- D The soil directly
Correct answer: Cocoons
The clitellum secretes a cocoon into which eggs and stored sperm are deposited. Fertilization and subsequent development of the embryos into juvenile worms take place within this cocoon, which is left in the soil.
The development of earthworms is described as:
- A Indirect with a trochophore larva
- B Direct with no larval stage
- C Indirect with a caterpillar stage
- D Parthenogenetic
Correct answer: Direct with no larval stage
Earthworms show direct development. There is no larval stage; the cocoons produce small, fully-formed juvenile earthworms after about three weeks.
The dorsal surface of the body in an earthworm is primarily distinguished from the ventral surface by the presence of a:
- A Dark mid-dorsal line
- B Series of genital pores
- C Row of S-shaped setae
- D Prominent clitellum
Correct answer: Dark mid-dorsal line
The dark mid-dorsal line represents the dorsal blood vessel visible through the body wall. The ventral surface is distinguished by the presence of genital openings.
Which structure in the earthworm serves as a wedge to force open cracks in the soil and possesses a sensory function?
- A Peristomium
- B Prostomium
- C Clitellum
- D Pygidium
Correct answer: Prostomium
The prostomium is a small lobe-like structure that hangs over the mouth. It acts as a sensory organ and helps the earthworm push through the soil.
The first body segment of the earthworm, which contains the mouth, is known as the:
- A Prostomium
- B Peristomium
- C Protostomia
- D Metamere
Correct answer: Peristomium
The peristomium, also called the buccal segment, is the first segment of the body and surrounds the mouth opening.
In a mature earthworm, which segments are covered by a prominent dark band of glandular tissue known as the clitellum?
- A 12, 13, 14
- B 14, 15, 16
- C 16, 17, 18
- D 18, 19, 20
Correct answer: 14, 15, 16
The clitellum is a glandular thickening of the body wall found specifically in segments 14 to 16, which plays a major role in cocoon formation.
Four pairs of spermathecal apertures are located ventro-laterally in the intersegmental grooves of which segments?
- A 4/5, 5/6, 6/7, 7/8
- B 5/6, 6/7, 7/8, 8/9
- C 14/15, 15/16, 16/17, 17/18
- D 17/18, 18/19, 19/20, 20/21
Correct answer: 5/6, 6/7, 7/8, 8/9
Spermathecal apertures are found in the grooves between segments 5 and 9. These pores lead to the spermathecae where spermatozoa are stored during copulation.
Where is the single female genital pore situated in the earthworm Pheretima?
- A Mid-ventral line of segment 14
- B Ventro-lateral side of segment 18
- C Mid-dorsal line of segment 16
- D Intersegmental groove of 14/15
Correct answer: Mid-ventral line of segment 14
A single female genital pore is located on the mid-ventral line of the 14th segment, within the region of the clitellum.
In Pheretima (earthworm), a pair of male genital pores is present on the ventro-lateral sides of which segment?
- A 14th segment
- B 16th segment
- C 18th segment
- D 20th segment
Correct answer: 18th segment
In Pheretima the male genital pores are paired and open on the ventro-lateral sides of the 18th segment. The female genital pore is single and lies mid-ventrally on the 14th segment, and the four pairs of spermathecal pores lie in segments 5 to 9.
The S-shaped setae, used for locomotion in earthworms, are present in all segments EXCEPT:
- A First segment and clitellum
- B First, last, and clitellum
- C Segments 14 to 16 only
- D The last ten segments
Correct answer: First, last, and clitellum
Setae are embedded in epidermal pits and help in movement, but they are absent in the first segment, the last segment, and the clitellum.
The body wall of the earthworm consists of several layers. Which is the outermost non-cellular layer?
- A Epidermis
- B Cuticle layer
- C Circular muscle layer
- D Coelomic epithelium
Correct answer: Cuticle layer
The outermost covering of the earthworm is a thin, non-cellular, transparent layer called the cuticle, which is secreted by the underlying epidermis.
In the alimentary canal of the earthworm, the muscular gizzard is found in segments:
- A 1-3
- B 5-7
- C 8-9
- D 15-26
Correct answer: 8-9
The gizzard is a highly muscular organ located in segments 8 and 9. It helps in grinding soil particles and decaying leaves.
Calciferous glands are present in the stomach of the earthworm to:
- A Secrete digestive enzymes for proteins
- B Emulsify fats
- C Grind the food into a fine paste
- D Neutralize the humic acid in humus
Correct answer: Neutralize the humic acid in humus
Calciferous glands found in the stomach wall secrete calcium carbonate to neutralize the acidity of the humic acid found in the organic matter the worm consumes.
The typhlosole is an internal median fold of the dorsal wall of the intestine. Its primary function is to:
- A Secrete intestinal juice
- B Grind soil particles
- C Increase absorption area
- D Store undigested waste
Correct answer: Increase absorption area
The typhlosole is a characteristic feature of the earthworm intestine starting from the 26th segment (except the last 23-25 segments) that increases the surface area for nutrient absorption.
Earthworms possess a closed circulatory system. Blood glands are present in which segments?
- A 1, 2, and 3
- B 7, 8, and 9
- C 10, 11, and 12
- D 4, 5, and 6
Correct answer: 4, 5, and 6
Blood glands are located in segments 4, 5, and 6. They produce blood cells and hemoglobin, which is dissolved in the blood plasma.
The type of nephridia attached to the lining of the body wall from segment 3 to the last are:
- A Pharyngeal nephridia
- B Septal nephridia
- C Integumentary nephridia
- D Enteronephric nephridia
Correct answer: Integumentary nephridia
Integumentary nephridia are small structures attached to the body wall. They open to the exterior through nephridiopores and are found from segment 3 to the last.
Which nephridia are found as three paired tufts in segments 4, 5, and 6?
- A Septal nephridia
- B Integumentary nephridia
- C Pharyngeal nephridia
- D Avicular nephridia
Correct answer: Pharyngeal nephridia
Pharyngeal nephridia occur as three pairs of tufts in the 4th, 5th, and 6th segments. Their ducts open into the buccal cavity and pharynx.
The nervous system of the earthworm features a nerve cord that is:
- A Dorsal, hollow, and single
- B Lateral and triple
- C Dorsal, solid, and double
- D Ventral, solid, and double
Correct answer: Ventral, solid, and double
As an invertebrate, the earthworm has a ventral, solid, and double nerve cord with segmental ganglia.
In Pheretima (earthworm), the two pairs of testes are located in which segments?
- A 10 and 11
- B 12 and 13
- C 14 and 15
- D 18 and 19
Correct answer: 10 and 11
Pheretima is hermaphrodite. Its two pairs of testes lie in the 10th and 11th segments, and the vasa deferentia carry sperm back to the male genital pores on the 18th segment. The seminal vesicles of segments 11 and 12 are the common wrong pick here — they store sperm but do not produce it.
Ovaries in Pheretima are found attached at the inter-segmental septum of segments:
- A 10/11
- B 14/15
- C 18/19
- D 12/13
Correct answer: 12/13
One pair of ovaries is present, attached to the inter-segmental septum between the 12th and 13th segments.
Where does the fertilization and development of the earthworm zygote occur?
- A Inside the spermathecae
- B Within the soil
- C Inside the cocoons
- D Within the oviducal funnel
Correct answer: Inside the cocoons
Fertilization and embryo development occur within cocoons, which are deposited in or on the soil. There is no larval stage in their development.
The blood cells of the earthworm are characterized as being:
- A Red and nucleated
- B Containing hemoglobin within the cell
- C Produced in the gizzard
- D Phagocytic in nature
Correct answer: Phagocytic in nature
Blood cells in earthworms are phagocytic. Hemoglobin is not in the cells but is dissolved in the blood plasma.