Grade 10 Chapter 13: Life Processes in Living Organisms Part - 2

Introduction

Life processes are the essential functions that maintain homeostasis and sustain life in all living organisms. In this chapter, we continue our exploration of vital life processes, focusing on respiration, circulation, and excretion in plants and animals. These processes are fundamental to the survival of all living organisms and demonstrate the remarkable adaptations that have evolved across different species.

Respiration in Living Organisms

Types of Respiration

Respiration is the process by which organisms obtain energy from organic compounds, typically glucose. There are two main types of respiration:

1. Aerobic Respiration: Requires oxygen and produces more energy
2. Anaerobic Respiration: Occurs without oxygen and produces less energy

Aerobic Respiration

The complete equation for aerobic respiration is:

C₆H₁₂O₆ + 6O₂ → 6CO₂ + 6H₂O + Energy (ATP)

This process occurs in three main stages:

1. Glycolysis: Occurs in the cytoplasm and breaks down glucose into pyruvate
2. Krebs Cycle: Takes place in the mitochondrial matrix and generates NADH and FADH₂
3. Electron Transport Chain: Located in the inner mitochondrial membrane, produces most of the ATP

Anaerobic Respiration

When oxygen is limited or absent, organisms can perform anaerobic respiration:

1. Lactic Acid Fermentation: Occurs in muscle cells during intense exercise

   C₆H₁₂O₆ → 2C₃H₆O₃ (Lactic acid) + Energy (2 ATP)

2. Alcoholic Fermentation: Occurs in yeast and some bacteria

   C₆H₁₂O₆ → 2C₂H₅OH (Ethanol) + 2CO₂ + Energy (2 ATP)

Respiratory System in Animals

Human Respiratory System

The human respiratory system consists of:

1. Nasal Cavity: Filters, warms, and moistens incoming air
2. Pharynx: Common passage for air and food
3. Larynx: Contains vocal cords and prevents food from entering the trachea
4. Trachea: Windpipe lined with ciliated epithelium and mucus-secreting cells
5. Bronchi and Bronchioles: Branch into smaller airways leading to alveoli
6. Alveoli: Tiny air sacs where gas exchange occurs
7. Diaphragm: Muscle that facilitates breathing by changing the volume of the thoracic cavity

Mechanism of Breathing in Humans

Breathing involves two phases:

1. Inhalation (Inspiration):
   • Diaphragm contracts and flattens
   • External intercostal muscles contract, raising the ribs
   • Thoracic cavity volume increases
   • Pressure in lungs decreases below atmospheric pressure
   • Air rushes into the lungs
2. Exhalation (Expiration):
   • Diaphragm relaxes and moves upward
   • External intercostal muscles relax, lowering the ribs
   • Thoracic cavity volume decreases
   • Pressure in lungs increases above atmospheric pressure
   • Air is forced out of the lungs

Gas Exchange

Gas exchange occurs at the alveoli through diffusion:

• Oxygen diffuses from alveoli into the blood
• Carbon dioxide diffuses from the blood into alveoli
• Factors affecting gas exchange include:
  • Surface area of alveoli (approximately 70-80 m²)
  • Thickness of alveolar-capillary membrane (0.5 μm)
  • Concentration gradient of gases
  • Ventilation-perfusion ratio

Transport of Respiratory Gases

Oxygen and carbon dioxide are transported in the blood:

1. Oxygen Transport:
   • 97-98% bound to hemoglobin in red blood cells as oxyhemoglobin (HbO₂)
   • 2-3% dissolved in plasma
2. Carbon Dioxide Transport:
   • 70% as bicarbonate ions (HCO₃⁻) in plasma
   • 23% bound to hemoglobin as carbaminohemoglobin
   • 7% dissolved in plasma

Respiratory Systems in Other Animals

Different animals have evolved various respiratory structures:

1. Insects: Tracheal system with spiracles, tracheae, and tracheoles
2. Fish: Gills with gill filaments and lamellae for aquatic respiration
3. Amphibians: Skin, buccal cavity, and lungs for both aquatic and terrestrial respiration
4. Birds: Highly efficient lungs with air sacs for unidirectional airflow

Respiration in Plants

Mechanism of Gaseous Exchange

Plants exchange gases through specialized structures:

1. Stomata: Small pores on leaf surfaces controlled by guard cells
2. Lenticels: Porous tissues in woody stems and roots
3. Pneumatophores: Specialized aerial roots in mangrove plants

Cellular Respiration in Plants

Plants perform both aerobic and anaerobic respiration:

• Aerobic respiration occurs continuously in all living plant cells
• Anaerobic respiration occurs in waterlogged roots or during seed germination
• The rate of respiration is influenced by:
  • Temperature
  • Oxygen availability
  • Developmental stage
  • Type of tissue

Relationship Between Photosynthesis and Respiration

Plants perform both photosynthesis and respiration:

• Photosynthesis: 6CO₂ + 6H₂O + Light energy → C₆H₁₂O₆ + 6O₂
• Respiration: C₆H₁₂O₆ + 6O₂ → 6CO₂ + 6H₂O + Energy
• During daylight, the rate of photosynthesis exceeds respiration
• At night, only respiration occurs
• The compensation point is when the rate of photosynthesis equals the rate of respiration

Circulatory System in Animals

Types of Circulatory Systems

Animals have evolved different types of circulatory systems:

1. Open Circulatory System:
   • Blood flows through open spaces called hemocoel
   • Found in arthropods and most mollusks
   • Less efficient but requires less energy
2. Closed Circulatory System:
   • Blood flows within vessels
   • Found in vertebrates, annelids, and cephalopods
   • More efficient but requires more energy

Human Circulatory System

The human circulatory system consists of:

1. Heart: Four-chambered muscular organ that pumps blood
2. Blood Vessels:
   • Arteries: Carry blood away from the heart
   • Veins: Carry blood toward the heart
   • Capillaries: Allow exchange of materials between blood and tissues
3. Blood: Fluid connective tissue consisting of plasma and formed elements

Structure and Function of the Human Heart

The human heart has four chambers:

1. Right Atrium: Receives deoxygenated blood from the body via the superior and inferior vena cavae
2. Right Ventricle: Pumps deoxygenated blood to the lungs via the pulmonary artery
3. Left Atrium: Receives oxygenated blood from the lungs via the pulmonary veins
4. Left Ventricle: Pumps oxygenated blood to the body via the aorta

The heart is separated by septa and has valves to ensure unidirectional blood flow:

• Atrioventricular (AV) Valves:
  • Tricuspid valve: Between right atrium and right ventricle
  • Bicuspid (mitral) valve: Between left atrium and left ventricle
• Semilunar Valves:
  • Pulmonary valve: Between right ventricle and pulmonary artery
  • Aortic valve: Between left ventricle and aorta

Cardiac Cycle and Heart Sounds

The cardiac cycle consists of:

1. Atrial Systole: Contraction of atria (0.1 seconds)
2. Ventricular Systole: Contraction of ventricles (0.3 seconds)
3. Diastole: Relaxation of all chambers (0.4 seconds)

Heart sounds are produced by the closing of valves:

• "Lubb" (First sound): Closure of AV valves at the beginning of ventricular systole
• "Dupp" (Second sound): Closure of semilunar valves at the beginning of ventricular diastole

Blood Pressure and Pulse

Blood pressure is the force exerted by blood against the walls of blood vessels:

• Systolic Pressure: Pressure during ventricular contraction (120 mmHg)
• Diastolic Pressure: Pressure during ventricular relaxation (80 mmHg)
• Normal blood pressure is expressed as 120/80 mmHg

Pulse is the rhythmic expansion and recoil of arteries due to the pumping action of the heart:

• Normal resting pulse rate: 72-80 beats per minute
• Factors affecting pulse rate include age, physical activity, emotions, and health conditions

Double Circulation

Humans have a double circulatory system:

1. Pulmonary Circulation:
   • Right ventricle → Pulmonary artery → Lungs → Pulmonary veins → Left atrium
   • Deoxygenated blood becomes oxygenated
2. Systemic Circulation:
   • Left ventricle → Aorta → Body tissues → Venae cavae → Right atrium
   • Oxygenated blood becomes deoxygenated

Composition and Functions of Blood

Blood consists of:

1. Plasma (55%):
   • Water (90-92%)
   • Proteins (albumin, globulin, fibrinogen)
   • Nutrients, hormones, waste products, gases
2. Formed Elements (45%):
   • Red Blood Cells (Erythrocytes): Transport oxygen
   • White Blood Cells (Leukocytes): Provide immunity
   • Platelets (Thrombocytes): Aid in blood clotting

Functions of blood include:

• Transport of respiratory gases, nutrients, hormones, and waste products
• Regulation of body temperature, pH, and fluid balance
• Protection against pathogens and blood loss
• Clotting to prevent excessive bleeding

Blood Groups and Transfusion

The ABO blood group system is based on the presence or absence of antigens on red blood cells:

• Type A: Has A antigen and anti-B antibody
• Type B: Has B antigen and anti-A antibody
• Type AB: Has both A and B antigens and no antibodies
• Type O: Has no antigens and both anti-A and anti-B antibodies

The Rh factor is another important blood group system:

• Rh+: Has Rh antigen
• Rh-: Does not have Rh antigen

Blood transfusion compatibility:

• Type O- is the universal donor
• Type AB+ is the universal recipient
• Incompatible transfusions can cause agglutination (clumping) of red blood cells

Lymphatic System

The lymphatic system complements the circulatory system:

• Collects excess tissue fluid and returns it to the bloodstream
• Absorbs fats from the digestive system
• Plays a crucial role in immune responses
• Components include lymph, lymph vessels, lymph nodes, and lymphoid organs (thymus, spleen, tonsils)

Transport in Plants

Xylem Transport

Xylem transports water and minerals from roots to shoots:

1. Components of Xylem:
   • Tracheids: Elongated cells with tapered ends
   • Vessels: Tube-like structures formed by vessel elements
   • Xylem parenchyma: Living cells for storage
   • Xylem fibers: Provide mechanical support
2. Mechanism of Water Transport:
   • Root pressure: Osmotic pressure in root cells pushes water upward
   • Capillary action: Water rises in narrow tubes due to adhesion and cohesion
   • Transpiration pull: Evaporation of water from leaves creates negative pressure
   • Cohesion-tension theory: Water molecules form a continuous column due to cohesive forces

Phloem Transport

Phloem transports organic nutrients (mainly sucrose) throughout the plant:

1. Components of Phloem:
   • Sieve tubes: Conducting cells with sieve plates
   • Companion cells: Regulate the function of sieve tubes
   • Phloem parenchyma: Storage cells
   • Phloem fibers: Provide mechanical support
2. Mechanism of Translocation:
   • Pressure flow hypothesis (Münch hypothesis)
   • Source (e.g., leaves): Loading of sucrose creates high osmotic pressure
   • Sink (e.g., roots, fruits): Unloading of sucrose creates low osmotic pressure
   • Pressure gradient drives the flow of phloem sap

Transpiration

Transpiration is the loss of water vapor from plant surfaces, primarily through stomata:

1. Types of Transpiration:
   • Stomatal transpiration (90-95%): Through stomata
   • Cuticular transpiration (5-10%): Through cuticle
   • Lenticular transpiration: Through lenticels
2. Factors Affecting Transpiration:
   • Environmental factors: Light intensity, temperature, humidity, wind speed
   • Plant factors: Leaf area, leaf structure, stomatal density, root-shoot ratio
3. Significance of Transpiration:
   • Creates transpiration pull for water transport
   • Cools the plant through evaporative cooling
   • Maintains turgidity and shape of cells
   • Helps in mineral salt distribution

Excretion in Living Organisms

Excretion in Humans

Excretion is the removal of metabolic waste products from the body:

1. Excretory Organs:
   • Kidneys: Remove nitrogenous wastes, regulate water and electrolyte balance
   • Lungs: Eliminate carbon dioxide and water vapor
   • Skin: Removes water, salts, and small amounts of urea through sweat
   • Liver: Produces urea from ammonia, breaks down toxins
2. Structure of the Urinary System:
   • Kidneys: Bean-shaped organs that filter blood
   • Ureters: Tubes that carry urine from kidneys to bladder
   • Urinary bladder: Temporary storage of urine
   • Urethra: Tube that carries urine from bladder to outside

Structure and Function of the Kidney

Each kidney contains about one million nephrons, the functional units of the kidney:

1. Parts of a Nephron:
   • Bowman's capsule: Cup-shaped structure that surrounds the glomerulus
   • Glomerulus: Tuft of capillaries where filtration occurs
   • Proximal convoluted tubule: Reabsorption of glucose, amino acids, and ions
   • Loop of Henle: Creates concentration gradient for water reabsorption
   • Distal convoluted tubule: Regulation of potassium, sodium, and pH
   • Collecting duct: Final water reabsorption and urine concentration
2. Urine Formation:
   • Glomerular filtration: Blood pressure forces water and small molecules into Bowman's capsule
   • Tubular reabsorption: Useful substances are reabsorbed into the bloodstream
   • Tubular secretion: Additional waste products are secreted into the tubule

Composition of Urine

Normal human urine consists of:

• Water (95%)
• Urea (2%): Main nitrogenous waste product
• Uric acid: From nucleic acid metabolism
• Creatinine: From muscle metabolism
• Inorganic salts: Sodium, potassium, chloride, etc.
• Pigments: Urochrome gives urine its yellow color

Abnormal constituents that may indicate disease:

• Glucose (glycosuria): May indicate diabetes mellitus
• Proteins (proteinuria): May indicate kidney damage
• Blood (hematuria): May indicate infection or injury
• Ketone bodies (ketonuria): May indicate diabetes or starvation

Excretion in Other Animals

Different animals have evolved various excretory structures:

1. Protozoa: Contractile vacuoles
2. Flatworms: Flame cells (protonephridia)
3. Earthworms: Nephridia
4. Insects: Malpighian tubules
5. Birds and Reptiles: Metanephric kidneys that produce uric acid (semi-solid, conserves water)
6. Mammals: Metanephric kidneys that produce urea (liquid, requires more water)

Excretion in Plants

Plants have different mechanisms for waste removal:

1. Storage of Waste Products:
   • In vacuoles: Tannins, resins, gums
   • In cell walls: Calcium oxalate crystals
   • In older tissues: Heartwood of trees
2. Elimination of Wastes:
   • Leaf fall: Shedding leaves containing waste products
   • Exudation: Secretion of gums, resins through bark
   • Gaseous exchange: Release of CO₂ during respiration
3. Recycling of Waste Products:
   • Conversion of ammonia to amino acids
   • Reuse of some minerals during leaf senescence

Disorders of the Respiratory, Circulatory, and Excretory Systems

Respiratory Disorders

1. Asthma: Chronic inflammation of airways causing wheezing, coughing, and breathing difficulty
2. Bronchitis: Inflammation of bronchi, often due to infection or irritants
3. Pneumonia: Infection causing inflammation of alveoli, filled with fluid
4. Tuberculosis (TB): Bacterial infection primarily affecting lungs
5. Emphysema: Destruction of alveolar walls, reducing surface area for gas exchange
6. Lung Cancer: Uncontrolled growth of cells in lung tissue, often linked to smoking

Circulatory Disorders

1. Hypertension: Persistently elevated blood pressure (>140/90 mmHg)
2. Coronary Artery Disease: Narrowing of coronary arteries due to atherosclerosis
3. Myocardial Infarction (Heart Attack): Death of heart muscle due to blocked blood supply
4. Stroke: Disruption of blood supply to the brain
5. Anemia: Reduced hemoglobin or red blood cell count
6. Leukemia: Cancer of blood-forming tissues, characterized by abnormal white blood cells

Excretory Disorders

1. Kidney Stones: Solid masses formed from minerals in urine
2. Urinary Tract Infection (UTI): Bacterial infection in any part of the urinary system
3. Nephritis: Inflammation of the kidneys
4. Renal Failure: Kidneys unable to filter waste products from blood
5. Dialysis: Artificial process to remove waste products when kidneys fail
6. Kidney Transplantation: Surgical replacement of a failed kidney with a healthy donor kidney

Summary

Life processes such as respiration, circulation, and excretion are essential for maintaining homeostasis in living organisms. These processes involve specialized structures and mechanisms that have evolved to meet the specific needs of different organisms. Understanding these processes helps us appreciate the complexity and diversity of life on Earth and provides insights into the treatment and prevention of various disorders.

Practice Questions

1. Compare and contrast aerobic and anaerobic respiration.
2. Explain the mechanism of breathing in humans.
3. Describe the structure and function of the human heart.
4. How does the transport of water in plants differ from the transport of organic nutrients?
5. Explain the process of urine formation in the human kidney.
6. Compare excretion in terrestrial and aquatic animals.
7. Discuss the relationship between the respiratory and circulatory systems.
8. How do plants manage their waste products differently from animals?