RBSE Solutions Class 11 Biology Chapter 35 Earthworm

RBSE Class 11 Biology Chapter 35 Multiple Choice Objective Questions

Question 1. First segment of earthworm is-
(a) Prostomium
(b) Peristomium
(c) Pygiduim
(d) Clitellum
Answer: (b) Peristomium
In simple words: The peristomium is the first body segment of an earthworm, encircling the mouth. It is the part you would see right at the very front.

🎯 Exam Tip: Remember that the peristomium contains the mouth, while the prostomium is a small, fleshy lobe that overhangs the mouth but is not a true segment.

Question 2. Select female reproductive organ-
(a) Seminal vesicle
(b) Spermathecae
(c) Accessory glands
(d) Prostate gland
Answer: (b) Spermathecae
In simple words: Spermathecae are special bags or sacs that female earthworms have to store sperm from another earthworm after mating.

🎯 Exam Tip: Distinguish between male and female reproductive organs. Seminal vesicles, accessory glands, and prostate glands are involved in male reproduction, while spermathecae store received sperm.

Question 4. Where the respiratory pigment forms in earthworm-
(a) External skin
(b) Heart
(c) Blood glands
(d) Lymph glands
Answer: (c) Blood glands
In simple words: In earthworms, the pigment that helps carry oxygen in their blood is made inside special "blood glands" found in their body.

🎯 Exam Tip: Understand that earthworms don't have lungs like humans. Their blood glands are crucial for producing respiratory pigments to help transport gases throughout their body.

Question 5. Site of fertilization in earthworm-
(a) Cocoon
(b) Seminal vesicle
(c) Oviduct
(d) Moist soil
Answer: (a) Cocoon
In simple words: Earthworms do not fertilize inside their bodies. Instead, both the eggs and stored sperm are released into a protective case called a cocoon, where fertilization happens.

🎯 Exam Tip: Remember that earthworm fertilization is external, occurring within the cocoon, which acts as a safe environment for the developing embryos.

RBSE Class 11 Biology Chapter 35 Very Short Answer Questions

Question 1. Write scientific name of earthworm.
Answer: The scientific name for an earthworm is Pheretima posthuma.
In simple words: The specific scientific name for this type of earthworm is Pheretima posthuma.

🎯 Exam Tip: Always capitalize the first letter of the genus (Pheretima) and keep the species name (posthuma) in lowercase, and underline or italicize the full scientific name.

Question 2. Site of fertilization in earthworm.
Answer: Fertilization in earthworms happens in the 10th & 11th segments.
In simple words: The process where egg and sperm join takes place in the earthworm's 10th and 11th body parts.

🎯 Exam Tip: Pinpoint the exact segments where key biological processes like fertilization occur, as this level of detail is often tested.

Question 4. What is the length of a mature earthworm?
Answer: A fully grown earthworm is usually between 15 to 20 cm long.
In simple words: Adult earthworms typically measure 15 to 20 centimeters in length.

🎯 Exam Tip: Be precise with numerical answers like measurements and quantities.

Question 5. What is the main function of gizzard?
Answer: The main job of the gizzard is grinding food into smaller pieces.
In simple words: The gizzard helps earthworms break down their food into very small bits.

🎯 Exam Tip: When asked for the "main" function, provide the most important role of the organ clearly and concisely.

Question 6. Which blood vessel in earthworm functions as true heart?
Answer: The dorsal blood vessel acts like a true heart in an earthworm.
In simple words: The main blood vessel on the top side of the earthworm works like its heart.

🎯 Exam Tip: Note that earthworms have a simpler circulatory system, and a "true heart" equivalent is often a muscular blood vessel.

Question 7. Give the name of structure found in the intestine of earthworm meant for absorption.
Answer: The structure found in the earthworm's intestine for absorbing nutrients is called the typhlosole.
In simple words: The typhlosole in the intestine helps the earthworm take in food nutrients.

🎯 Exam Tip: Relate the function (absorption) directly to the specific structure (typhlosole) to show clear understanding.

Question 8. Where the calciferous glands are found in earthworm?
Answer: Calciferous glands are located in the stomach of the earthworm.
In simple words: Earthworms have calciferous glands inside their stomach.

🎯 Exam Tip: Remember that the stomach is a key digestive organ where these glands help neutralize acids from the soil.

Question 9. Between which segments, first inter segment septum is found in earthworm.
Answer: The first septum that divides segments in an earthworm is found between the 4th and 5th segments (usually expressed as 4/5).
In simple words: The first dividing wall between body parts in an earthworm is between segments 4 and 5.

🎯 Exam Tip: Learn the numbering of segments where important anatomical features begin or end in earthworms.

Question 11. What is the name of excretory unit in earthworm?
Answer: The excretory unit in an earthworm is called a nephridium.
In simple words: Earthworms use nephridia to get rid of waste from their bodies.

🎯 Exam Tip: The nephridium is similar in function to kidneys in higher animals, highlighting its role in waste removal.

Question 12. The reason of brown color of skin of earthworm.
Answer: The brown color of an earthworm's skin comes from a pigment called porphyrin.
In simple words: Earthworms have a brown color because of a special substance in their skin called porphyrin.

🎯 Exam Tip: Specific pigments often determine an animal's natural coloration; knowing these names can be important.

Question 13. Which muscle layer is most developed in the gizzard of earthworm.
Answer: The circular muscles are the most developed layer in the earthworm's gizzard.
In simple words: The gizzard has very strong circular muscles that help it grind food.

🎯 Exam Tip: Muscle development in an organ often relates directly to its primary function, such as grinding in the gizzard.

Question 14. Segment of earthworm in which ovaries are situated?
Answer: The ovaries in an earthworm are found in the 13th segment.
In simple words: The earthworm's ovaries, where eggs are made, are in the 13th body segment.

🎯 Exam Tip: Knowing the precise segment locations of reproductive organs is crucial for understanding earthworm anatomy.

Question 15. Name the ecotonephric nephridia in earthworm.
Answer: The integumentary nephridia are ecotonephric in an earthworm.
In simple words: The integumentary nephridia are a type of excretory organ found in the earthworm's skin.

🎯 Exam Tip: Understand the different types of nephridia (e.g., integumentary, septal, pharyngeal) and their locations and specific classifications (e.g., ecotonephric, enteronephric).

RBSE Class 11 Biology Chapter 35 Short Answer Questions

Question 1. What do you mean by metameric segment?
Answer: Metameric segmentation means an animal's body is divided both on the inside and the outside into many similar, separate sections or chambers. Each segment can have its own organs and functions.
In simple words: Metameric segmentation means the body is made of many similar parts, both inside and out.

🎯 Exam Tip: Explain both the external and internal division to fully define metameric segmentation, a key characteristic of annelids like earthworms.

Question 3. Which cell types are found in the body wall of earth-worm.
Answer: The earthworm's body wall mainly consists of the epidermis. This epidermis is a single layer of columnar cells.
Most cells in the epidermis are supporting cells. Some other cells change to form gland cells, which are of two kinds:

• Mucous gland cells: These cells are spread all over the body. They produce mucus to keep the body moist.
• Albumin gland cells: These are fewer in number and make albumin. Most of them are found in the clitellum's body wall.
• Some epidermal cells also change to become sensory cells. The epidermis also has a few small, round, or cone-shaped basal cells.

🎯 Exam Tip: When listing cell types, mention their specific functions and, if applicable, their distribution within the body wall.

Question 4. Why earthworm is called as friend of farmers?
Answer: Earthworms are called "friends of farmers" because their burrowing activity makes the soil porous, much like a honeycomb. This porous soil allows for better air circulation (respiration) and easier root penetration for plants, leading to healthier growth and better crops.
In simple words: Earthworms dig tunnels in the soil, which helps air get in and plant roots grow better. That's why farmers like them.

🎯 Exam Tip: Focus on the direct benefits of earthworm activity to soil structure and plant growth when explaining their importance to farmers.

Question 5. Explain the process of ingestion in earthworm.
Answer: An earthworm feeds using its buccal cavity (mouth) and pharynx. The buccal cavity moves in and out repeatedly to gather soil. At the same time, the pharynx sucks in the soil like a pump, helping the earthworm ingest its food.
In simple words: The earthworm pushes out its mouth to grab soil, then its throat sucks the soil inside like a vacuum cleaner.

🎯 Exam Tip: Describe the coordinated action of the buccal cavity and pharynx to show a complete understanding of the ingestion process.

Question 6. What will be the effect on digestion if the calciferous glands of stomach stop functioning?
Answer: If the calciferous glands in the stomach stop working, there will be no further digestion in the earthworm's alimentary canal. This is because the digestive process needs an alkaline pH, which these glands normally help to maintain.
In simple words: If the calciferous glands stop, the earthworm's food won't digest properly because the gut needs to stay alkaline, which these glands help with.

🎯 Exam Tip: Highlight the specific role of calciferous glands in pH regulation and how their failure impacts the overall digestive process.

Question 8. Draw a labelled diagram of spermatheca and write its role.
Answer:
Spermathecae: Earthworms have four pairs of spermathecae. These are located on the sides, towards the bottom, in segments 6th, 7th, 8th, and 9th. They open to the outside through pores between segments 5/6, 6/7, 7/8, and 8/9. Their main job is to store sperm received from another earthworm during mating.
In simple words: Spermathecae are sacs in segments 6-9 that store sperm received from another earthworm during mating.

🎯 Exam Tip: When a diagram is requested, accurately label all relevant parts and ensure the accompanying text clearly explains the function of the structure.

Question 9. Explain the process of cocoon formation in earthworm.
Answer:
Cocoon Formation: The cocoon in an earthworm is made by the clitellum. After mating, the modified epidermal cells of the clitellum release a slimy substance. This substance hardens into a girdle around the clitellum when it touches the air. The clitellum then receives albumin protein, which feeds the developing embryo. Many ova (eggs) are then released into this girdle. It is believed that the girdle contracts to push the ova out from the oviducts.
In simple words: After mating, the clitellum makes a slimy band that hardens into a cocoon. Eggs are put inside this cocoon with food, and the cocoon then slides off the worm.

🎯 Exam Tip: Detail the role of the clitellum, the sequence of secretions, and how eggs are deposited and sealed within the cocoon.

Question 10. What is the relation of spermathecae with reproduction?
Answer: Spermathecae are directly related to reproduction as they are responsible for storing sperm after copulation (mating) with another earthworm. This stored sperm is later used to fertilize the earthworm's own eggs within the cocoon.
In simple words: Spermathecae store sperm after mating, which is then used to fertilize the eggs.

🎯 Exam Tip: Clearly state the function of spermathecae in the context of sexual reproduction and cross-fertilization in earthworms.

Question 11. Earthworm is bisexual than why self fertilization is not found.
Answer: Even though earthworms are bisexual (having both male and female organs), they do not self-fertilize. This is mainly to prevent genetic disorders by promoting genetic diversity through cross-fertilization. Additionally, earthworms are protandrous, meaning their male reproductive organs mature before their female organs, further hindering self-fertilization.
In simple words: Earthworms don't self-fertilize to avoid genetic problems and because their male parts mature before their female parts.

🎯 Exam Tip: Explain both the genetic advantage (preventing disorders, promoting diversity) and the physiological reason (protandry) for the absence of self-fertilization.

Question 12. Give an account of coelomic corpuscles in earthworm.
Answer: The body cavity of the earthworm is filled with coelomic fluid, which is milky white and alkaline (with a pH of 7 to 9). This fluid contains several types of coelomic corpuscles:

• Mucocytes: These are cells that produce mucus.
• Chlorogogen cells: These cells are involved in metabolic functions, similar to the liver.

🎯 Exam Tip: Remember to describe the nature of the coelomic fluid (color, pH) and list the different types of corpuscles, along with their primary roles.

Question 13. Explain process of locomotion in earthworm.
Answer: Earthworms primarily move by extending and contracting their bodies using two main sets of muscles: circular and longitudinal muscles. They also use small bristles called setae to grip the ground. When circular muscles contract, the body becomes longer and thinner, pushing the front part forward. When longitudinal muscles contract, the body shortens and thickens, pulling the rear part along. This alternating action allows the earthworm to crawl.
In simple words: Earthworms move by stretching and squeezing their body muscles and using tiny bristles to hold onto the ground, pushing themselves forward.

🎯 Exam Tip: Focus on the coordinated contraction and relaxation of both circular and longitudinal muscles, along with the role of setae, for a complete explanation of locomotion.

Question 14. Why earthworm respires through the skin?
Answer: Earthworms breathe through their skin because they do not have specialized respiratory organs like lungs or gills. Their moist body surface allows for the direct exchange of gases (oxygen in, carbon dioxide out) with the environment. If their skin dries out, they cannot absorb oxygen and will suffocate.
In simple words: Earthworms breathe through their skin because they don't have special breathing organs, and their moist skin helps them take in oxygen.

🎯 Exam Tip: Emphasize the absence of dedicated respiratory organs and the importance of a moist body surface for cutaneous respiration in earthworms.

Question 15. Give the main functions of body wall in earthworm.
Answer: The earthworm's body wall has several key functions:

• It protects the internal organs of the earthworm.
• It acts as a respiratory organ, allowing gas exchange through its moist surface.
• It bears sense organs, helping the earthworm detect its surroundings.

🎯 Exam Tip: List the protective, respiratory, and sensory functions of the body wall to provide a comprehensive answer.

RBSE Class 11 Biology Chapter 35 Essay Type Questions

Question 1. Describe the digestive system in earthworm. Give suitable diagram.
Answer:
Alimentary Canal: The earthworm has a simple, straight tube for its digestive system, running from the mouth to the anus. This arrangement is often described as a "tube within a tube" body plan.
The alimentary canal includes the following parts:

• Mouth: This is the opening at the very front of the earthworm, shaped like a crescent.
• Buccal cavity: Located in the first three body segments, this part can extend out. It helps the earthworm gather soil.
• Pharynx: This part sucks in soil like a pump because it has radial muscles.
• Oesophagus: A small, narrow tube in segments 5th, 6th, and 7th. It has many folds inside.
• Gizzard: A bulb-shaped structure in the 8th segment. Its wall is thick with circular muscles and is lined by a hard, chitinous cuticle. The gizzard's main job is to grind food.
• Stomach: This is a thin, tube-like structure from segments 9th to 14th. Its wall has glands and internal folds. It has special calciferous gland cells that secrete calcium carbonate, which neutralizes humic acid and makes the digestive environment alkaline.
• Intestine: This is a sac-like and tubular structure that runs from the 14th segment to the last. It is divided into three parts:
  • Pre-typhlosolar region: Found from segments 14th to 26th, this part does not have a typhlosole. In the 26th segment, it gives rise to a pair of intestinal caecae, which extend up to the 23rd segment and secrete digestive enzymes.
  • Typhlosolar region: This region extends from the 27th segment almost to the very end. It has a typhlosole, which is an internal fold on the top-middle side. The typhlosole increases the surface area for food absorption.
  • Post-typhlosolar region: This part is the last 25 segments without a typhlosole and is also called the rectum.
• Anus: This is a slit-like opening at the very end of the body, through which waste is expelled.

🎯 Exam Tip: Describe each part of the alimentary canal in sequence, mentioning its segment location, structure, and specific function to give a complete picture of digestion.

Question 2. Explain blood vascular system in earthworm.
Answer:
Blood Vessels: The earthworm's blood vascular system includes three main blood vessels and many smaller assisting blood vessels.
Main blood vessels:

• Dorsal blood vessel: This vessel is located above the alimentary canal. It acts as a pumping and collecting vessel. The blood flows from the back to the front. In the posterior part (from the last to the 14th segment), it collects blood. In the anterior part (first thirteen segments), it distributes blood to the alimentary canal and reproductive organs.
• Ventral blood Vessel: Located below the alimentary canal from the 2nd to the last segment. It is thin-walled, less muscular, and non-contractile, meaning it doesn't pump. It also lacks valves. Blood flows from the front to the back. It acts as a distributing vessel throughout the body, supplying blood to the body wall, integumentary nephridia, intestine, septa, septal nephridia, and reproductive organs from the 14th segment to the last.
• Lateral-oesophageal and Sub-Neural blood Vessel: The sub-neural blood vessel runs along the middle-bottom side, just below the alimentary canal, from the 14th to the last segment. It is thin-walled, non-muscular, and non-contractile, and it has no valves. The blood in the sub-neural blood vessel flows from front to back, acting as a collecting vessel. In the 14th segment, the sub-neural blood vessel splits into two lateral oesophageal blood vessels. These are located on both sides of the alimentary canal in the first thirteen segments. The lateral oesophageal blood vessels collect blood from organs in the first thirteen segments. The blood in these vessels flows from front to back.

• Ring Vessels: There are 6 pairs of small ring vessels found in the stomach wall. They collect blood from the stomach and carry it into the supra-gastric blood vessel.
• Anterior loops: There are 2 pairs of anterior loops in the 10th and 11th segments. They connect the lateral-oesophageal blood vessels to the supra-oesophageal blood vessels. These loops are non-contractile and do not have valves.
• Hearts: Earthworms have four pairs of tubular, non-contractile hearts in segments 7th, 9th, 12th, and 13th. The hearts in segments 7th and 9th are called lateral hearts. Each lateral heart has 4 pairs of valves. They connect the dorsal blood vessel to the ventral blood vessel. The hearts in segments 12th and 13th connect the dorsal blood vessel and supra-oesophageal blood vessel to the ventral.
• Commissural BV: A pair of commissural blood vessels is found in each segment from the 14th to the last. They connect the sub-neural blood vessel to the dorsal blood vessel. Each commissural blood vessel gives off a small septo-intestinal blood vessel, which supplies blood to the septum and the intestine.
• Ventro-tegumentary BV: The ventral blood vessel gives out a pair of ventro-tegumentary blood vessels in each body segment. They supply blood to the body wall and integumentary nephridia of that segment. The dorsal blood vessel collects blood from these areas.
• Ventro-intestinal & Dorso-Intestinal B.Vs.: The ventral blood vessel gives out one ventro-intestinal blood vessel in each segment from the 14th to the last. It supplies blood to the intestinal wall, where it forms two blood networks: outer intestinal plexus and inner intestinal plexus. Both plexuses are connected. Dorso-intestinal blood vessels collect blood from the intestinal wall. Each segment has 2 pairs of dorso-intestinal blood vessels.

🎯 Exam Tip: Clearly distinguish between collecting and distributing vessels, specify the segments where main vessels are located, and explain the roles of accessory structures like hearts and specialized blood vessels.

Question 3. Give the nature of eathworm concern to excretion. Give the staicture of septal nephridia in earthworm
Answer:
Excretion: Earthworms are ureotelic, meaning they excrete urea, but they also get rid of a mix of ammonia, urea, and creatinine. The proportions are roughly 55% ammonia, 40% urea, and 5% creatinine, especially during the rainy season.
3. Septal nephridia: Septal nephridia are also called typical nephridia and are endonephric (meaning they release waste internally) or enteronephric type.
Structure of septal nephridia: It consists of the following parts:

• Nephrostome: This is a funnel-shaped structure with two lips that are made of ciliated cells. The upper lip has 8 or 9 large marginal cells, and the lower lip has 4 or 5 small marginal cells. The funnel's opening is a tunnel inside a large central cell, which leads into the neck.
• Neck: A small, narrow tube that has cilia inside.
• Nephridial body: This is the main part of the septal nephridium, divided into two parts:
  • (a) Straight lobe
  • (b) Twisted lobe
• Terminal duct: This duct starts from the twisted lobe and has only one tubule.
• Septal excretory ducts: The terminal ducts from 20-25 septal nephridia in a group open into a single septal excretory duct. Each segment has 4 septal excretory ducts.
• Supra-intestinal excretory canals: There are two canals located mid-dorsally on the intestine, from the 15th segment to the last.

🎯 Exam Tip: When describing excretion, specify the waste products and their proportions. For the septal nephridia, detail each structural component (nephrostome, neck, body, ducts) and its role in the excretory process.

Question 4. Draw a labelled diagram of reproductive system of earthworm and write its role.
Answer: Earthworms have a complete reproductive system. They are hermaphrodites, meaning each earthworm has both male and female reproductive organs. The spermathecae are a key part of this system. There are four pairs of spermathecae, located on the sides towards the bottom, in segments 6, 7, 8, and 9. These open to the outside through pores between segments 5/6, 6/7, 7/8, and 8/9. The main role of the spermathecae is to store sperm after the earthworm mates. Overall, the reproductive system's role is to allow earthworms to produce offspring, ensuring the continuation of their species.
In simple words: The earthworm has both male and female parts. Special sacs called spermathecae store sperm after mating. The whole system helps them make baby earthworms.

🎯 Exam Tip: While drawing, ensure all reproductive organs are clearly labelled and correctly placed according to the segment numbers. For the "role" part, explain the function of the main reproductive structures.

Question 5. Explain the body wall of earthworm with the help of a diagram.
Answer: The earthworm's body wall is its outer covering, which protects it and helps in movement. It has several layers:

• Epidermis: This is the outermost layer. It is made of a single layer of tall, column-shaped cells. Most of these are supporting cells. Some epidermal cells change to become gland cells, which are of two types:
  • Mucous gland cells: These are found all over the body and make mucus to keep the skin moist, which is important for breathing.
  • Albumin gland cells: These are fewer in number and mainly found in the clitellum (a thick band around the body). They produce albumin, which provides food for the developing embryo inside the cocoon.
  Some epidermal cells also become sensory cells, helping the earthworm feel its surroundings.
• Musculature: Below the epidermis, there are three layers of muscles:
  • Outer circular muscles: These run around the body.
  • Middle longitudinal muscles: These run along the length of the body.
  • Inner circular muscles: These are located inside.
  The longitudinal muscles are usually thicker. These muscle layers help the earthworm to contract and extend its body for movement. The porphyrin pigment, responsible for the earthworm's brownish color, is found in the outer layer of circular muscles.
• Peritoneum: This is the innermost layer of the body wall, also known as coelomic epithelium. It is made of flat cells. The body wall, especially the clitellum, secretes the cocoon during the breeding season. The body wall gives the earthworm its shape and protects its internal organs.

🎯 Exam Tip: When describing the body wall, remember to detail the different layers (epidermis, musculature, peritoneum) and their specific functions, such as mucus secretion, movement, and protection. Mentioning the different types of cells or muscle layers adds depth to the answer.