Solution:: Chapter 6: Life Process

 

Page No-81 Questions 

Answers to Questions:

1. Why is diffusion insufficient to meet the oxygen requirements of multicellular organisms like humans?

   • In multicellular organisms, body cells are not in direct contact with the environment.
   • Diffusion is a slow process and cannot efficiently transport oxygen to all cells in larger organisms.
   • Specialized systems like the respiratory and circulatory system are needed to transport oxygen efficiently throughout the body.

2. What criteria do we use to decide whether something is alive?

   • Movement (visible or at the molecular level).
   • Growth and development over time.
   • Respiration (energy release from food).
   • Response to stimuli (reaction to the environment).
   • Reproduction (ability to produce offspring).
   • Excretion (removal of waste products).

3. What are outside raw materials used for by an organism?

   • Food – for energy and growth.
   • Oxygen – for respiration and energy release.
   • Water and minerals – for biochemical reactions and cellular functions.

4. What processes would you consider essential for maintaining life?

• Nutrition – Intake of food for energy and growth.
• Respiration – Breakdown of food to release energy.
• Transport – Distribution of nutrients and oxygen.
• Excretion – Removal of waste materials.
• Reproduction – Ensuring continuity of life.

Page No-87 Questions 

1. What are the differences between autotrophic nutrition and heterotrophic nutrition?

Feature	Autotrophic Nutrition	Heterotrophic Nutrition
Organisms Involved	Plants, algae, some bacteria	Animals, fungi, some bacteria
Food Source	Synthesizes its own food	Depends on other organisms for food
Process	Photosynthesis (in most cases)	Ingestion and digestion of food
Raw Materials	CO₂, water, sunlight	Organic substances from plants/animals
Dependency	Independent (self-feeding)	Dependent on other organisms

2. Where do plants get each of the raw materials required for photosynthesis?

• Carbon dioxide (CO₂): Absorbed from the air through stomata in leaves.
• Water (H₂O): Absorbed from the soil by roots and transported via xylem.
• Sunlight: Captured by chlorophyll in chloroplasts.
• Chlorophyll: Present in leaf cells, absorbs sunlight for energy conversion.

3. What is the role of the acid in our stomach?

• Hydrochloric acid (HCl) creates an acidic medium for digestion.
• Helps in the activation of pepsin, an enzyme that breaks down proteins.
• Kills harmful bacteria present in food, preventing infections.

4. What is the function of digestive enzymes?

• Digestive enzymes break down complex food molecules into simpler, absorbable forms.
• Amylase (in saliva) breaks down starch into sugars.
• Pepsin (in stomach) digests proteins into peptides.
• Lipase (from pancreas) breaks down fats into fatty acids and glycerol.
• Trypsin (from pancreas) further digests proteins into amino acids.

5. How is the small intestine designed to absorb digested food?

• Long and coiled structure increases surface area for absorption.
• Villi and microvilli (finger-like projections) further enhance surface area.
• Rich blood supply in villi helps in rapid nutrient absorption into the bloodstream.
• Thin walls allow easy diffusion of nutrients.
• Lacteals (lymphatic vessels) absorb fats and transport them.

Page No-91  Questions 

1. What advantage over an aquatic organism does a terrestrial organism have with regard to obtaining oxygen for respiration?

Terrestrial organisms breathe in atmospheric oxygen, which is present in much higher concentration compared to the dissolved oxygen in water. This allows them to obtain oxygen more efficiently. Aquatic organisms, like fish, rely on gills to extract oxygen from water, but since water contains less oxygen than air, they have to work harder to obtain sufficient oxygen.

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2. What are the different ways in which glucose is oxidized to provide energy in various organisms?

Glucose is oxidized through two main types of respiration:

1. Aerobic Respiration (in presence of oxygen):

   • Occurs in most plants and animals.
   • Glucose is broken down completely into carbon dioxide (CO₂) and water (H₂O), releasing a large amount of energy (ATP).
   • Reaction: $$C_6H_{12}O_6 + 6O_2 → 6CO_2 + 6H_2O + Energy (ATP)$$

2. Anaerobic Respiration (in absence of oxygen):

   • Occurs in some microorganisms like yeast and also in human muscle cells during strenuous activity.
   • In Yeast (Fermentation): $$Glucose → Ethanol + CO_2 + Energy$$
   • In Human Muscles (during heavy exercise): $$Glucose → Lactic Acid + Energy$$
   • Anaerobic respiration produces less energy compared to aerobic respiration.

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3. How is oxygen and carbon dioxide transported in human beings?

• Oxygen Transport:

  • Oxygen is carried by haemoglobin in red blood cells.
  • Haemoglobin binds to oxygen in the lungs and forms oxyhaemoglobin.
  • This oxygen-rich blood is transported to body tissues, where oxygen is released for cellular respiration.

• Carbon Dioxide Transport:

  • Carbon dioxide is transported mainly in dissolved form in the blood plasma.
  • Some CO₂ binds to haemoglobin, forming carbaminohaemoglobin.
  • It is carried back to the lungs, where it diffuses into the alveoli and is expelled during exhalation.

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4. How are the lungs designed in human beings to maximize the area for exchange of gases?

• Millions of Alveoli: The lungs contain millions of tiny air sacs called alveoli, which provide a huge surface area for gas exchange.
• Thin Walls: Alveoli have thin walls (one cell thick) that allow easy diffusion of gases.
• Dense Capillary Network: Alveoli are surrounded by a dense network of blood capillaries, ensuring efficient gas exchange.
• Moist Surface: The alveolar walls remain moist, helping in the dissolution and diffusion of gases.
• Constant Airflow: The process of inhalation and exhalation maintains a continuous supply of fresh oxygen and removes carbon dioxide.

Page No-96 Questions 

1. What are the components of the transport system in human beings? What are the functions of these components?

The transport system in human beings consists of:

1. Heart – A muscular organ that pumps blood throughout the body.
2. Blood vessels – These include:
   • Arteries (carry oxygenated blood from the heart to the body).
   • Veins (carry deoxygenated blood back to the heart).
   • Capillaries (tiny vessels that allow exchange of oxygen, nutrients, and waste between blood and tissues).
3. Blood – The fluid medium that carries gases, nutrients, hormones, and waste. It consists of:
   • Red blood cells (RBCs) – Transport oxygen using hemoglobin.
   • White blood cells (WBCs) – Defend against infections.
   • Platelets – Help in blood clotting.
   • Plasma – The liquid part that carries nutrients, hormones, and waste.

2. Why is it necessary to separate oxygenated and deoxygenated blood in mammals and birds?

• Mammals and birds are warm-blooded and maintain a constant body temperature.
• They have a high metabolic rate, requiring an efficient supply of oxygen.
• Separation of oxygenated and deoxygenated blood:
  • Ensures efficient oxygen delivery to body cells.
  • Prevents mixing, allowing a higher energy yield from respiration.
  • Helps maintain body temperature (homeostasis) in warm-blooded animals.

3. What are the components of the transport system in highly organised plants?

• Highly organised plants have two major transport tissues:

1. Xylem – Transports water and minerals from roots to leaves.
2. Phloem – Transports food (sucrose), amino acids, and hormones throughout the plant.

4. How are water and minerals transported in plants?

• Water and minerals are absorbed by roots and transported through xylem by:
  1. Root Pressure – Pushes water up from the roots.
  2. Capillary Action – Water rises due to adhesion and cohesion forces.
  3. Transpiration Pull – Water evaporates from leaves, creating suction that pulls water upwards.

5. How is food transported in plants?

• Food (mainly sucrose) is transported through phloem by a process called translocation.
• The mechanism involves:
1. Loading of sucrose into phloem using ATP energy.
2. Osmotic pressure increase, causing water to move in from xylem.
3. Flow of food solution from source (leaves) to sink (roots, fruits, storage organs).
4. Unloading of sucrose at the required site for growth, storage, or energy use.

Page No-96 Questions 

1. Describe the structure and functioning of nephrons.

Structure of Nephrons:

• Nephrons are the structural and functional units of the kidney responsible for urine formation.
• Each nephron consists of:
  1. Bowman’s capsule – A cup-shaped structure that encloses a cluster of capillaries called the glomerulus.
  2. Glomerulus – A network of capillaries where filtration of blood occurs.
  3. Renal tubule – A long tube where reabsorption and secretion take place, consisting of:
     • Proximal Convoluted Tubule (PCT) – Selective reabsorption of nutrients.
     • Loop of Henle – Helps in water and salt balance.
     • Distal Convoluted Tubule (DCT) – Further ion regulation.
  4. Collecting duct – Collects urine and sends it to the ureter.

Functioning of Nephrons:

1. Filtration – Blood enters the glomerulus, and waste, excess water, and small molecules are filtered into Bowman’s capsule.
2. Reabsorption – Useful substances (glucose, amino acids, water, salts) are reabsorbed in the renal tubule.
3. Secretion – Additional waste materials (ions, urea) are secreted into the tubule.
4. Urine Formation – The final filtrate (urine) passes through the collecting duct into the ureter and then to the urinary bladder for excretion.

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2. What are the methods used by plants to get rid of excretory products?

Plants use several strategies for excretion:

1. Gaseous Exchange:

   • Oxygen (O₂) from photosynthesis is released through stomata.
   • Carbon dioxide (CO₂) from respiration is expelled through stomata and lenticels.

2. Transpiration:

   • Excess water is removed through stomata in leaves.

3. Storage in Dead Tissues:

   • Waste products like resins, gums, and latex are stored in old xylem or bark.

4. Leaf Shedding:

   • Harmful wastes accumulate in leaves and are eliminated when the leaves fall off.

5. Storage in Vacuoles:

   • Plants store some waste in vacuoles, making them harmless.

6. Excretion into Soil:

   • Some plants release toxic chemicals into the soil (e.g., walnut trees release allelopathic substances).

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3. How is the amount of urine produced regulated?

The amount of urine produced depends on:

1. Water Balance:

   • If water intake is high, more urine is produced.
   • If water intake is low, less urine is produced to conserve water.

2. Hormonal Regulation:

   • The Antidiuretic Hormone (ADH) controls water reabsorption in the kidneys.
   • When water levels in the body are low, ADH increases water reabsorption, reducing urine output.

3. Salt and Waste Levels:

   • Higher salt or waste levels lead to increased urine production to remove excess substances.

4. Temperature and Activity:

   • In hot weather or during exercise, more water is lost through sweating, reducing urine output.
   • In cold weather, less sweating occurs, leading to increased urine production.

5. Blood Pressure:

   • High blood pressure increases the filtration rate in nephrons, producing more urine.

Thus, urine production is regulated by water intake, hormones, temperature, and body needs.

Exercise 

1. The kidneys in human beings are a part of the system for

(a) nutrition
(b) respiration
(c) excretion ✅
(d) transportation

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2. The xylem in plants are responsible for

(a) transport of water ✅
(b) transport of food
(c) transport of amino acids
(d) transport of oxygen

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3. The autotrophic mode of nutrition requires

(a) carbon dioxide and water
(b) chlorophyll
(c) sunlight
(d) all of the above ✅

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4. The breakdown of pyruvate to give carbon dioxide, water, and energy takes place in

(a) cytoplasm
(b) mitochondria ✅
(c) chloroplast
(d) nucleus

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5. How are fats digested in our bodies? Where does this process take place?

• Fats are digested in the small intestine.
• Bile (from the liver) emulsifies fats, breaking them into smaller droplets.
• Lipase enzyme (from the pancreas) breaks fats into fatty acids and glycerol.
• The digestion occurs mainly in the duodenum (first part of the small intestine).

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6. What is the role of saliva in the digestion of food?

• Saliva is secreted by salivary glands and contains salivary amylase (ptyalin).
• It converts starch into maltose (a simpler sugar).
• Saliva also moistens food, making it easier to swallow and begin digestion.

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7. What are the necessary conditions for autotrophic nutrition, and what are its byproducts?

Necessary conditions:

1. Sunlight – provides energy.
2. Chlorophyll – absorbs light for photosynthesis.
3. Carbon dioxide (CO₂) – taken from the air.
4. Water (H₂O) – absorbed from the soil.

Byproducts:

• Glucose (C₆H₁₂O₆) – used as food.
• Oxygen (O₂) – released into the air.

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8. What are the differences between aerobic and anaerobic respiration? Name some organisms that use the anaerobic mode of respiration.

Feature	Aerobic Respiration	Anaerobic Respiration
Oxygen Requirement	Requires oxygen	Does not require oxygen
Location	Occurs in mitochondria	Occurs in cytoplasm
End Products	CO₂, H₂O, and energy (ATP)	Lactic acid (in muscles) or alcohol + CO₂ (in yeast)
Energy Release	High (36-38 ATP molecules)	Low (2 ATP molecules)

Examples of organisms using anaerobic respiration:

• Yeast (produces alcohol and CO₂).
• Bacteria (some anaerobic species).
• Muscle cells (under oxygen deficiency, produce lactic acid).

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9. How are the alveoli designed to maximize the exchange of gases?

• Large surface area – Millions of alveoli provide a huge exchange surface.
• Thin walls – Allow easy diffusion of gases.
• Rich blood supply – Surrounded by capillaries for efficient gas exchange.
• Moist lining – Helps dissolve gases for better diffusion.

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10. What would be the consequences of a deficiency of haemoglobin in our bodies?

• Haemoglobin is responsible for oxygen transport in red blood cells.
• A deficiency leads to anaemia, causing:
  • Fatigue and weakness (due to low oxygen supply).
  • Shortness of breath (less oxygen carried to tissues).
  • Paleness of skin (low red blood cell count).
  • Dizziness and headaches (oxygen deficiency in the brain).

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11. Describe double circulation of blood in human beings. Why is it necessary?

Double Circulation:

• Pulmonary Circulation:
  • Right ventricle → Lungs → Left atrium (carries deoxygenated blood to the lungs and brings back oxygenated blood).
• Systemic Circulation:
  • Left ventricle → Body → Right atrium (pumps oxygenated blood to the body and returns deoxygenated blood).

Why is it necessary?

• Ensures complete separation of oxygenated and deoxygenated blood.
• Increases efficiency of oxygen supply to the body.
• Maintains high pressure for faster circulation in warm-blooded animals (mammals & birds).

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12. What are the differences between the transport of materials in xylem and phloem?

Feature	Xylem	Phloem
Function	Transports water and minerals	Transports food (sugars)
Direction	Unidirectional (roots to leaves)	Bidirectional (from leaves to other parts)
Components	Tracheids, vessels, fibers	Sieve tubes, companion cells
Energy Use	Passive transport (no energy)	Active transport (requires energy)

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13. Compare the functioning of alveoli in the lungs and nephrons in the kidneys with respect to their structure and functioning.

Feature	Alveoli (Lungs)	Nephrons (Kidneys)
Function	Gas exchange (O₂ in, CO₂ out)	Filtration and excretion of waste
Structure	Small air sacs with thin walls	Tube-like structures with Bowman’s capsule
Capillary Network	Surrounded by capillaries for gas exchange	Surrounded by capillaries for filtration
Process	Oxygen enters blood, CO₂ leaves	Blood filtered, waste removed as urine

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