Life Processes Section-2 (Transportation & Excretion) - Class 10 MCQ

The component responsible for oxygen transport in blood is:
RBC (Red Blood Cells)
- Red blood cells, also known as erythrocytes, are the most abundant cells in the blood.
- They contain a protein called hemoglobin, which binds to oxygen molecules.
- Hemoglobin carries oxygen from the lungs to the body's tissues and organs.
- RBCs have a unique shape and flexibility that allows them to squeeze through narrow blood vessels and deliver oxygen efficiently.
- They have a lifespan of about 120 days and are continuously produced in the bone marrow to replace old or damaged cells.
Other blood components:
- WBC (White Blood Cells) are responsible for the immune response and fighting against infections.
- Platelets are involved in blood clotting to prevent excessive bleeding.
- Plasma is the liquid component of blood that carries nutrients, hormones, and waste products.
In summary:
Red blood cells, or RBCs, play a crucial role in transporting oxygen throughout the body. Their unique structure and hemoglobin content enable them to efficiently bind and carry oxygen to the body's tissues and organs.

Answer:
The average lifespan of red blood cells (RBCs) is 120 days. Here's a detailed explanation:
Red Blood Cells (RBCs)
- Red blood cells, also known as erythrocytes, are the most common type of blood cells in our body.
- They play a crucial role in transporting oxygen from the lungs to different tissues and organs.
- RBCs contain a protein called hemoglobin, which binds with oxygen and carries it throughout the body.
Lifespan of RBCs
- The lifespan of RBCs varies depending on the individual, but on average, it is approximately 120 days.
- After this time, RBCs become old and less flexible, making it difficult for them to pass through narrow blood vessels.
- The spleen and liver help remove old or damaged RBCs from the circulation.
Production of New RBCs
- To maintain a constant supply of RBCs in the body, new ones are continuously produced to replace the old ones.
- This process occurs in the bone marrow, where stem cells differentiate into mature RBCs.
- The production of RBCs is regulated by a hormone called erythropoietin, which is released by the kidneys in response to low oxygen levels.
Conclusion
- The average lifespan of red blood cells is 120 days.
- Regular production of new RBCs ensures a constant supply in the body and helps maintain optimal oxygen transport.

Role of Platelets:
Platelets play a crucial role in the process of blood clotting, which is essential for wound healing and preventing excessive bleeding. Here are the key functions of platelets:
1. Hemostasis:
- Platelets are responsible for maintaining the integrity of blood vessels by forming a plug at the site of injury. This process is known as hemostasis.
- When a blood vessel is damaged, platelets adhere to the site and aggregate together, forming a temporary clot to stop bleeding.
2. Clot Formation:
- Platelets release various chemicals, such as ADP and thromboxane, which attract more platelets to the site of injury and enhance clot formation.
- They also release fibrinogen, a protein that helps in the formation of fibrin threads, which strengthen the clot.
3. Clot Retraction:
- After clot formation, platelets contract, pulling the edges of the wound closer together and reducing the size of the clot.
- This process, known as clot retraction, helps in stabilizing the clot and promoting wound healing.
4. Wound Healing:
- Platelets release growth factors, such as platelet-derived growth factor (PDGF) and transforming growth factor-beta (TGF-beta), which stimulate the repair and regeneration of damaged tissues.
- These growth factors promote the migration of cells involved in wound healing, such as fibroblasts and endothelial cells.
5. Immune Response:
- While platelets are primarily known for their clotting function, they also play a role in the immune response.
- Platelets can interact with immune cells, such as neutrophils and macrophages, and release immune mediators that contribute to inflammation and immune defense.
In conclusion, platelets are essential for blood clotting and wound healing. They form clots at the site of injury, release growth factors for tissue repair, and participate in the immune response.

To determine the chamber of the heart where the blood from systemic circulation first comes, we need to understand the pathway of blood flow through the heart. Here is a detailed explanation:
1. Systemic Circulation:
- Systemic circulation refers to the movement of oxygenated blood from the heart to the rest of the body and the return of deoxygenated blood from the body back to the heart.
- This circulation supplies oxygen and nutrients to various organs and tissues and removes waste products.
2. Pathway of Blood Flow through the Heart:
- The blood from systemic circulation enters the heart through the superior and inferior vena cava, which are two large veins.
- The blood then flows into the right atrium, which is the first chamber of the heart that receives deoxygenated blood.
- From the right atrium, the blood moves into the right ventricle through the tricuspid valve.
- The right ventricle then pumps the deoxygenated blood to the lungs for oxygenation.
3. Conclusion:
- Based on the pathway of blood flow through the heart, we can conclude that the blood from systemic circulation first comes to the right atrium, not the right auricle as mentioned in the options A.
- Therefore, the correct answer is B: Right atrium.
Note: The right auricle is not a specific chamber of the heart; it refers to an extension of the right atrium that increases its capacity to hold blood.

Answer:
The chamber of the heart that pushes the blood into systemic circulation is the left ventricle. Here is a detailed explanation:
1. Introduction:
The heart consists of four chambers: two atria and two ventricles. The atria receive blood from various parts of the body, while the ventricles pump the blood out to the rest of the body.
2. Function of the ventricles:
The ventricles are responsible for pumping blood out of the heart and into circulation. They have thicker muscular walls compared to the atria, as they need to generate enough force to push blood throughout the body.
3. Left ventricle:
The left ventricle is the chamber that receives oxygenated blood from the left atrium and pumps it into the systemic circulation. It is the most muscular chamber of the heart because it needs to generate enough pressure to push blood through the entire body.
4. Systemic circulation:
Systemic circulation refers to the pathway of blood flow from the left ventricle, through the aorta, and into the arteries that supply oxygenated blood to the various tissues and organs of the body. This is where oxygen and nutrients are delivered to the cells, and waste products are removed.
5. Conclusion:
In conclusion, the left ventricle is responsible for pushing the blood into systemic circulation. Its strong muscular walls and powerful contractions enable it to pump oxygenated blood throughout the body, supplying vital nutrients and removing waste products.

Double Circulation in Animals:
Double circulation refers to the circulation of blood through two separate circuits in the body, namely the pulmonary circuit and the systemic circuit. This allows for efficient separation of oxygenated and deoxygenated blood, ensuring that oxygenated blood is delivered to the organs and tissues while deoxygenated blood is sent to the lungs for oxygenation.
Among the given options, the animal in which double circulation is well developed is the Bird (Option D). Here's why:
Fish (Option A):
- Fish have a single circulation system where blood flows through the gills for oxygenation and then directly to the body organs. There is no clear separation of oxygenated and deoxygenated blood.
Frog (Option B):
- Frogs have a three-chambered heart that allows for partial separation of oxygenated and deoxygenated blood.
- However, their circulatory system is not fully double circulation as there is mixing of oxygenated and deoxygenated blood in the ventricle.
Crocodile (Option C):
- Crocodiles have a four-chambered heart, which is a characteristic of animals with double circulation.
- However, crocodiles have a special adaptation called the foramen of Panizza, which allows some mixing of oxygenated and deoxygenated blood.
Bird (Option D):
- Birds have a complete double circulation system with a four-chambered heart.
- The pulmonary circuit carries deoxygenated blood from the heart to the lungs for oxygenation, and the systemic circuit carries oxygenated blood from the heart to the rest of the body.
- There is no mixing of oxygenated and deoxygenated blood, ensuring efficient oxygen delivery to the tissues.
In conclusion, the animal in which double circulation is well developed is the Bird (Option D).

Initiation of the Heartbeat
The initiation of the heartbeat in the human heart is controlled by a specialized group of cells called the cardiac conduction system. The main components of the cardiac conduction system are:
1. SA Node (Sinoatrial Node):
The SA node is often referred to as the natural pacemaker of the heart. It is located in the right atrium and is responsible for initiating the electrical signals that regulate the heartbeat. The SA node generates electrical impulses, causing the atria to contract, and it sets the pace for the entire heart.
2. AV Node (Atrioventricular Node):
The AV node is located between the atria and the ventricles. It acts as a relay station, receiving the electrical signals from the SA node and delaying them slightly before transmitting them to the ventricles. This delay allows the atria to fully contract before the ventricles receive the signal to contract.
3. Bundle of His:
The Bundle of His is a specialized bundle of fibers that carries the electrical signals from the AV node down to the ventricles. It branches into two pathways known as the left and right bundle branches.
4. Purkinje Fibres:
The Purkinje fibers are a network of specialized conducting fibers that spread throughout the ventricles. These fibers transmit the electrical signals rapidly, causing the ventricles to contract and pump blood out of the heart.
Conclusion:
Out of these components, the SA node is responsible for initiating the heartbeat. It generates electrical impulses that spread through the atria and stimulate the rest of the cardiac conduction system, leading to the coordinated contraction of the heart chambers.

Functional Unit of Human Excretory System: Nephron
The functional unit of the human excretory system is called the nephron. The nephron is a microscopic structure located in the kidneys, responsible for the filtration, reabsorption, and secretion processes involved in urine formation. Here is a detailed explanation of the nephron's role in the excretory system:
1. Structure of the Nephron:
- The nephron consists of several components, including the renal corpuscle, proximal convoluted tubule, loop of Henle, distal convoluted tubule, and collecting duct.
- The renal corpuscle is composed of the glomerulus and Bowman's capsule, which initiate the filtration process.
2. Filtration:
- Blood enters the glomerulus, a network of capillaries, under high pressure.
- The glomerulus filters out waste products, excess water, and other substances from the blood.
- The filtrate, consisting of water, ions, glucose, urea, and other small molecules, enters the Bowman's capsule.
3. Reabsorption:
- As the filtrate passes through the proximal convoluted tubule, essential substances such as glucose, amino acids, and ions are selectively reabsorbed back into the bloodstream.
- The reabsorption process helps maintain the body's balance of water, electrolytes, and pH.
4. Secretion:
- The remaining filtrate, now called urine, continues to the loop of Henle and the distal convoluted tubule.
- The loop of Henle plays a crucial role in concentrating the urine by reabsorbing water and concentrating solutes.
- The distal convoluted tubule further adjusts the urine composition by secreting additional waste products and reabsorbing certain ions.
5. Collecting Duct:
- The urine then enters the collecting duct, where further water reabsorption occurs under the influence of antidiuretic hormone (ADH).
- The final urine, now concentrated and containing waste products, is transported to the renal pelvis and then to the bladder for storage and eventual elimination.
In conclusion, the nephron is the functional unit of the human excretory system. It performs vital processes like filtration, reabsorption, and secretion, ultimately producing urine and maintaining the body's fluid and electrolyte balance.

Main excretory product in humans: Urea

• Definition: Excretory products are waste substances that are eliminated from the body to maintain homeostasis. They are produced as a result of metabolic processes.


• Urea: Urea is the main excretory product in humans.


• Formation: Urea is formed in the liver when excess amino acids are broken down during protein metabolism.


• Transport: Urea is transported through the bloodstream to the kidneys for elimination.


• Role of Kidneys: The kidneys filter urea from the blood and excrete it in the form of urine.


• Concentration: The concentration of urea in the blood is regulated by the kidneys to maintain proper balance.


• Amount of Urea: On average, humans excrete about 25-30 grams of urea per day.

Therefore, the main excretory product in humans is urea, which is produced in the liver, transported through the bloodstream, and eliminated by the kidneys.

The main excretory product in lizards is Uric Acid.
Explanation:

• Lizards belong to a group of animals called reptiles, and like other reptiles, they excrete waste in the form of uric acid.


• Uric acid is a nitrogenous waste product that is relatively insoluble in water.


• Unlike mammals, which excrete urea as their main nitrogenous waste product, reptiles, including lizards, have evolved to excrete uric acid.


• Uric acid requires less water for excretion compared to urea, making it advantageous for reptiles living in dry environments.


• Lizards excrete uric acid in the form of a white, paste-like substance called urate.


• This urate is expelled from the lizard's body through the cloaca, which is a common opening for excretion and reproduction in reptiles.

In summary, the main excretory product in lizards is uric acid, which is excreted in the form of urate.

Respiratory pigment in human body is Haemoglobin.
Explanation:
Haemoglobin is the respiratory pigment found in the human body. Here is a detailed explanation:
- Respiratory Pigment: A respiratory pigment is a molecule that is responsible for transporting oxygen from the respiratory surface to the body tissues and carbon dioxide from the tissues to the respiratory surface. It enhances the oxygen-carrying capacity of the blood.
- Haemoglobin: Haemoglobin is a protein found in red blood cells (erythrocytes). It is composed of four subunits, each containing a heme group, which consists of an iron ion (Fe2+) bound to a porphyrin ring. This iron ion is responsible for binding and transporting oxygen molecules.
- Oxygen Transport: When oxygen is inhaled, it diffuses into the lungs and binds to the iron ions in the heme group of haemoglobin. This forms oxyhaemoglobin, which is bright red in color. Oxyhaemoglobin is then transported through the bloodstream to the body tissues.
- Carbon Dioxide Transport: Haemoglobin also plays a role in transporting carbon dioxide. Carbon dioxide is produced as a waste product in the body tissues and diffuses into the bloodstream. It binds to haemoglobin and forms carbaminohaemoglobin, which is then transported back to the lungs to be exhaled.
- Importance: Haemoglobin is essential for the proper functioning of the body as it ensures the delivery of oxygen to the cells and the removal of carbon dioxide. It helps maintain the pH balance of the blood and plays a crucial role in maintaining overall health and well-being.
In summary, haemoglobin is the respiratory pigment in the human body that enables the transport of oxygen and carbon dioxide.

Function of the Kidneys

The kidneys in human beings are primarily responsible for the process of excretion. Excretion is the removal of waste products from the body, including excess water, toxins, and metabolic waste.

Key Points:

• Kidneys are a part of the excretory system in human beings.


• They help regulate the balance of water, electrolytes, and acid-base levels in the body.


• Kidneys filter waste products and toxins from the blood to form urine.


• Urine is then transported through the urinary system and expelled from the body.


• The kidneys also play a role in regulating blood pressure and producing hormones that control red blood cell production.

It is important to note that while the kidneys are involved in the excretory system, they are not directly responsible for other functions such as nutrition, respiration, or transportation.

In conclusion, the kidneys are an essential part of the excretory system in human beings. They help remove waste products and maintain proper fluid and electrolyte balance in the body.

The oxygenated blood is carried from the lungs to the left auricle by the pulmonary vein.
The detailed solution is as follows:
Step 1: Introduction
- The oxygenated blood is the blood that has received oxygen from the lungs.
- The left auricle, also known as the left atrium, is one of the four chambers of the heart.
Step 2: Explanation
- The pulmonary vein is responsible for carrying the oxygenated blood from the lungs to the heart.
- The pulmonary vein is the only vein in the body that carries oxygenated blood.
- It connects the lungs to the left atrium of the heart.
- The left atrium receives the oxygenated blood from the pulmonary vein and pumps it into the left ventricle.
- From the left ventricle, the oxygenated blood is then pumped out of the heart and distributed to the rest of the body.
Step 3: Other options
- The vena cava is a large vein that carries deoxygenated blood from the body to the right atrium of the heart.
- The pulmonary artery carries deoxygenated blood from the right ventricle of the heart to the lungs for oxygenation.
- The aorta is the largest artery in the body and carries oxygenated blood from the left ventricle of the heart to the rest of the body.
Therefore, the correct answer is B: Pulmonary Vein.

To determine which group or groups of animals do not have a heart that pumps oxygenated blood to different parts of the body, let's analyze each option:
A: Pisces Only
- Pisces refers to fish.
- Fish have a heart that pumps oxygenated blood to different parts of their bodies.
- Therefore, option A is incorrect.
B: Amphibians Only
- Amphibians include frogs, toads, and salamanders.
- Amphibians have a three-chambered heart that pumps oxygenated blood to some parts of their bodies.
- Therefore, option B is incorrect.
C: Amphibians and reptiles only
- As mentioned earlier, amphibians have a three-chambered heart that pumps oxygenated blood to some parts of their bodies.
- Reptiles, on the other hand, have a three-chambered or four-chambered heart, depending on the species.
- Both amphibians and reptiles have a heart that pumps oxygenated blood to different parts of their bodies.
- Therefore, option C is incorrect.
D: Pisces and amphibians
- From the previous explanations, we know that both fish (Pisces) and amphibians have a heart that pumps oxygenated blood to different parts of their bodies.
- Therefore, option D is incorrect.
Therefore, the correct answer is None of the above or No group of animals in the given options.

To provide a detailed response to the question, it is important to break down the answer into headings and HTML bullet points. Here is the explanation:
The part of blood that provides immunity:
- The immune system plays a crucial role in protecting the body from foreign substances, such as bacteria and viruses.
- White blood cells (WBC) are the part of blood that provides immunity.
- WBCs are also known as leukocytes.
- They are responsible for defending the body against infection and disease.
- WBCs are produced in the bone marrow and are found circulating in the bloodstream and lymphatic system.
- There are different types of WBCs, including neutrophils, lymphocytes, monocytes, eosinophils, and basophils.
- Each type of WBC has a specific function in the immune response.
- Neutrophils are the most abundant type of WBC and are responsible for phagocytosis, which involves engulfing and destroying pathogens.
- Lymphocytes are responsible for the production of antibodies and are divided into B cells and T cells.
- B cells produce antibodies that target specific antigens, while T cells help coordinate the immune response.
- Monocytes are involved in phagocytosis and can differentiate into macrophages, which engulf and destroy pathogens.
- Eosinophils are involved in defending against parasitic infections and regulating allergic reactions.
- Basophils release histamine and other chemicals in response to allergens.
In summary, white blood cells (WBCs) are the part of blood that provides immunity. They play a crucial role in defending the body against infection and disease by various mechanisms, such as phagocytosis, antibody production, and coordination of the immune response.

Excretory materials are formed in every cell in the body. Here's a detailed explanation:
1. Introduction:
Excretory materials are waste products that are produced by the metabolic processes of cells in the body. These waste materials need to be eliminated to maintain the body's homeostasis.
2. Excretion in cells:
Each cell in the body produces waste products as it carries out its metabolic functions. These waste products include carbon dioxide, water, urea, and other metabolic byproducts. The excretory materials are formed as a result of cellular metabolism.
3. Role of organelles:
Different organelles within the cell play a role in the formation and elimination of excretory materials. For example:
- Mitochondria produce waste products such as carbon dioxide during cellular respiration.
- Peroxisomes help in the breakdown of toxic substances and the formation of hydrogen peroxide as a byproduct.
- Lysosomes are involved in the degradation of cellular waste materials.
4. Transport and elimination:
Once the excretory materials are formed in the cells, they need to be transported and eliminated from the body. This is achieved through various excretory organs and systems:
- Kidneys: The kidneys play a crucial role in filtering waste products from the blood and producing urine, which contains excretory materials such as urea, excess salts, and water.
- Rectum: The rectum is involved in the elimination of solid waste materials, such as undigested food particles and feces, through the process of defecation.
- Liver: The liver is responsible for the metabolism and detoxification of various substances in the body. It filters the blood and removes toxins, drugs, and metabolic waste products.
5. Conclusion:
In conclusion, excretory materials are formed in every cell in the body as a result of cellular metabolism. These waste products are then transported and eliminated by various excretory organs and systems, such as the kidneys, rectum, and liver.

The urinary bladder in mammals opens into the urethra. Here is a detailed explanation:
Introduction:
In mammals, the urinary bladder is an organ that stores urine produced by the kidneys before it is excreted out of the body. The bladder is connected to various other organs through different openings.
Answer:
The correct answer is B: Urethra.
Explanation:
The urinary bladder opens into the urethra, which is the tube responsible for carrying urine from the bladder to the outside of the body. The urethra serves as a passage for urine to exit the body during the process of urination.
Other options:
To provide further clarity, let's briefly explain the other options:
A: Uterus: The uterus is a female reproductive organ and is not directly related to the urinary system. In females, the urethra and the vagina have separate openings.
C: Vestibule: The vestibule is a part of the female reproductive system and is not directly associated with the urinary bladder.
D: Ureter: The ureter is a tube that carries urine from the kidneys to the urinary bladder. It does not connect directly to the bladder itself but rather to the upper part of the bladder.
In conclusion, the urinary bladder in mammals opens into the urethra, which serves as the pathway for urine to leave the body.

Urea formation in the body:
Introduction:
Urea is a waste product formed in the body during the breakdown of proteins. It is produced in a series of reactions known as the urea cycle or ornithine cycle. The urea cycle primarily takes place in the liver.
Key Points:
1. Liver: The liver is the primary site of urea formation in the body.
- The liver contains specialized cells called hepatocytes that have enzymes responsible for the urea cycle.
- These enzymes convert toxic ammonia, which is generated during protein metabolism, into urea.
- The urea is then transported to the kidneys for excretion in the urine.
2. Other organs:
- While the liver is the main site of urea production, other organs also contribute to the urea cycle.
- The kidneys play a crucial role in excreting urea by filtering it from the blood and eliminating it in the urine.
Conclusion:
Urea is primarily formed in the liver through a series of reactions known as the urea cycle. The liver converts toxic ammonia into urea, which is then excreted by the kidneys. Other organs, such as the kidneys, are involved in the elimination of urea from the body.

Explanation:
The yellow color of urine in vertebrates is due to a pigment called urochrome. Urochrome is a waste product that is produced when the body breaks down hemoglobin from red blood cells. It is responsible for the yellow color of urine.
Here is a detailed explanation of each option:
A: Cholesterol:
- Cholesterol is a lipid molecule and is not responsible for the yellow color of urine.
B: Urochrome:
- Urochrome is the correct answer. It is a pigment that gives urine its yellow color. It is a waste product of hemoglobin breakdown.
C: Uric acid:
- Uric acid is a waste product of protein metabolism and is not responsible for the yellow color of urine.
D: Melanin:
- Melanin is a pigment responsible for the coloration of skin, hair, and eyes. It is not involved in the color of urine.
Therefore, the correct answer is B: Urochrome.

Main functions of the kidney:

• Passive adsorption: The kidney passively adsorbs waste products, toxins, and excess ions from the blood.


• Ultrafiltration: The kidney performs ultrafiltration, which is the process of filtering blood through the glomerulus to form urine. This process removes waste products, excess water, and ions from the bloodstream.


• Selective reabsorption: After the initial filtration, the kidney selectively reabsorbs essential substances such as glucose, amino acids, and water back into the bloodstream. This ensures that important molecules are not lost in the urine.

Therefore, the correct answer is option D, which states that the main functions of the kidney are both ultrafiltration and selective reabsorption. Through these processes, the kidney helps maintain the body's fluid balance, electrolyte balance, and acid-base balance, while also excreting waste products and regulating blood pressure.