1. What Defines Living Beings?

  • Living beings exhibit activities like movement, growth, and breathing.
  • Visible movement is common evidence of life but not a defining feature (e.g., dormant plants and sleeping animals).
  • Invisible molecular movements within organisms are crucial for life.
  • Viruses lack molecular movement unless inside a host, leading to debate about whether they are alive.

2. Why Molecular Movement is Essential for Life

  • Living organisms are highly organized, with tissues, cells, and molecular structures.
  • Environmental factors can cause these structures to break down.
  • Molecular movement helps repair and maintain order in living systems.

3. What Are Life Processes?

  • Life processes are essential activities that maintain the structure and function of living organisms.
  • These processes include obtaining energy (nutrition), energy conversion (respiration), material transport, and waste removal (excretion).

4. Energy and Nutrition

  • Energy is needed for all maintenance processes.
  • Food serves as the source of energy and raw materials.
  • Life on Earth is carbon-based; organisms rely on carbon-based food sources.
  • Autotrophs (e.g., plants) create food using sunlight, carbon dioxide, and water.
  • Heterotrophs (e.g., animals, fungi) consume autotrophs or other organisms for energy.

5. Photosynthesis: Energy Creation in Autotrophs

  • Photosynthesis is the process where plants convert sunlight into chemical energy (carbohydrates).
  • Key Steps:
    1. Absorption of light by chlorophyll.
    2. Conversion of light energy to chemical energy and water splitting into oxygen and hydrogen.
    3. Reduction of carbon dioxide into carbohydrates.
  • Excess carbohydrates are stored as starch.

6. Leaf Structure and Gas Exchange

  • Photosynthesis occurs in chloroplasts found in leaf cells.
  • Stomata are tiny pores in leaves that allow gas exchange (CO₂ in, O₂ out).
  • Guard cells regulate stomata opening and closing to minimize water loss.

7. Other Raw Materials for Plant Growth

  • Water: Absorbed by roots and used in photosynthesis.
  • Minerals: Nitrogen, phosphorus, magnesium, and iron are absorbed from soil for protein and compound synthesis.
  • Nitrogen: Taken in as nitrates/nitrites or fixed from atmospheric nitrogen by bacteria.

8. Energy Utilization

  • Energy from food is used to:
    • Maintain body order.
    • Enable growth and synthesis of proteins.
  • Oxidation-reduction reactions in cells convert food into usable energy.

9. Transportation and Waste Management in Multicellular Organisms

  • Larger, complex organisms need transport systems for distributing nutrients and oxygen.
  • Waste products from metabolic reactions must be removed (excretion).
  • Specialized tissues perform these functions (e.g., circulatory and excretory systems).

Additional Insights for Competitive Exams

  • Characteristics of Life: Understand molecular movements, organization, and maintenance as core indicators of life.
  • Autotrophs vs. Heterotrophs:
    • Autotrophs: Use inorganic substances to create food.
    • Heterotrophs: Depend on autotrophs for energy.
  • Photosynthesis Key Formula:
    • 6CO2​+6H2​O  →​ C6​H12​O6​+6O2
  • Role of Minerals: Essential for metabolic functions and structural integrity of cells.
  • Adaptations in Desert Plants: Carbon fixation happens at night to conserve water.

Heterotrophic Nutrition

  • Organisms depend on others for food.
  • Nutrition depends on food type, availability, and how it is obtained.
  • Different strategies:
    1. External Digestion: Breakdown of food outside the body, e.g., fungi like bread moulds, yeast, and mushrooms.
    2. Internal Digestion: Food is ingested whole and broken down inside the body.
    3. Parasitic Nutrition: Nutrients are obtained from living hosts without killing them (e.g., cuscuta, ticks, lice, leeches).

How Organisms Obtain Nutrition

  • In single-celled organisms:
    • Amoeba: Uses extensions called pseudopodia to engulf food into a food vacuole. Digestion occurs inside the vacuole.
    • Paramoecium: Food enters a specific spot via cilia movement.

Human Nutrition

  • Food passes through the alimentary canal, a long tube with specialized regions.
  • Process:
    1. Mouth:
      • Food is crushed by teeth and mixed with saliva containing the enzyme salivary amylase to break starch into sugar.
      • Muscular tongue moves food.
    2. Esophagus: Moves food to the stomach via rhythmic contractions (peristalsis).
    3. Stomach:
      • Mixes food with gastric juice (contains HCl, pepsin, and mucus).
      • HCl provides acidity for pepsin activity and kills germs.
    4. Small Intestine:
      • Main site for digestion of carbohydrates, proteins, and fats.
      • Liver produces bile to emulsify fats, and pancreas secretes enzymes like trypsin (for proteins) and lipase (for fats).
      • Nutrients are absorbed through villi (finger-like projections) into the blood.
    5. Large Intestine:
      • Absorbs water and forms feces, which exit via the anus.

Key Concepts for Competitive Exams

  1. Enzymes: Biological catalysts (e.g., amylase, lipase). Know their functions.
  2. Digestion Time in Herbivores vs. Carnivores: Herbivores have longer intestines to digest cellulose.
  3. Role of Bile: Emulsifies fats, making enzyme action easier.
  4. Peristalsis: Essential for moving food through the digestive tract.

Respiration

  • Types:
    1. Aerobic Respiration: Uses oxygen to break down glucose into CO₂ and H₂O, releasing high energy.
    2. Anaerobic Respiration: Without oxygen; produces less energy (e.g., lactic acid in muscles).
  • ATP (Adenosine Triphosphate):
    • The “energy currency” of the cell.
    • Formed during respiration and used for cellular activities.
  • Respiratory Organs:
    • Plants: Use stomata for gas exchange.
    • Humans: Use lungs with alveoli to maximize surface area for gas exchange.
    • Aquatic Animals: Extract dissolved oxygen via gills.

Transportation in Humans

  • Blood:
    • Plasma: Carries nutrients and wastes.
    • RBCs (Red Blood Cells): Carry oxygen via hemoglobin.
    • WBCs: Fight infections.
  • Heart: Pumps blood throughout the body.
    • Double circulation system: Separates oxygen-rich and oxygen-poor blood.

Blood Pressure

  1. Definition: The force blood exerts on vessel walls.
  2. Types of Pressure:
    • Systolic Pressure: During heart contraction (normal: 120 mm Hg).
    • Diastolic Pressure: During heart relaxation (normal: 80 mm Hg).
  3. Comparison:
    • Higher in arteries (close to heart, high pressure).
    • Lower in veins (far from heart, low pressure).

Blood Vessels

  1. Arteries:
    • Carry blood away from the heart.
    • Thick, elastic walls to handle high pressure.
  2. Veins:
    • Bring blood back to the heart.
    • Thin walls, valves to prevent backflow.
  3. Capillaries:
    • Smallest vessels, one-cell-thick walls.
    • Enable material exchange between blood and tissues.

Platelets and Clotting

  1. Role of Platelets:
    • Help stop blood loss when vessels are injured.
    • Plug leaks by forming blood clots.
  2. Importance:
    • Prevents blood loss and maintains pressure for efficient circulation.

Lymph

  1. Definition: A clear fluid derived from blood plasma.
  2. Formation:
    • Plasma, proteins, and cells escape capillaries into tissues.
  3. Functions:
    • Carries fats from the intestine.
    • Drains excess fluid back into blood.
  4. Structure:
    • Lymphatic capillaries → Large lymph vessels → Veins.

Transport in Plants

  1. Raw Materials for Plants:
    • Water, minerals (from soil).
    • CO₂, light (for photosynthesis).
  2. Two Transport Systems:
    • Xylem: Moves water and minerals from roots upward.
    • Phloem: Distributes food (sugar) and other products both upward and downward.

Water Transport in Plants

  1. Root Pressure:
    • Roots absorb water by creating ion concentration differences.
    • Pushes water upward at night.
  2. Transpiration Pull:
    • Evaporation of water from leaves creates suction.
    • Main daytime force driving water upward.

Food Transport (Translocation)

  1. Phloem Function:
    • Transports sugars, amino acids, and other products.
    • Requires energy (ATP).
  2. Mechanism:
    • Increases osmotic pressure in phloem.
    • Moves substances to where they’re needed (e.g., growing buds, storage).

Excretion

  1. In Humans:
    • Organs: Kidneys, ureters, bladder, urethra.
    • Function: Filters nitrogenous waste (urea) and excess water from blood.
    • Unit: Nephron (basic filtering unit in kidneys).
    • Process:
      • Filtration in Bowman’s capsule.
      • Reabsorption of useful substances (e.g., glucose, water).
      • Waste forms urine.
  2. Artificial Kidney:
    • Used in kidney failure.
    • Removes wastes through dialysis without reabsorption.
  3. In Plants:
    • Oxygen (photosynthesis byproduct) diffuses out.
    • Excess water released by transpiration.
    • Wastes stored in vacuoles, old xylem, or shed with leaves.

Key Concepts for Competitive Exams

  1. Blood Pressure:
    • Know systolic/diastolic pressures and their significance.
    • Understand why arteries have thick walls and veins have valves.
  2. Plant Transport:
    • Difference between xylem (passive, water) and phloem (active, food).
    • Role of root pressure and transpiration pull.
  3. Excretion:
    • Structure of nephron and how filtration/reabsorption occurs.
    • Role of kidney dialysis.
  4. Extra Knowledge:
    • Transpiration helps regulate temperature in plants.
    • Lymphatic system plays a secondary role in immune defense and nutrient transport.