Life processes Complete - Class 10 AP Board Biology

Life Processes

Life processes are the essential functions carried out by living organisms to maintain life. These include nutrition, respiration, transportation, and excretion. Each process is vital for growth, energy production, material transfer, and waste elimination.

Characteristics of Living Organisms

Living organisms exhibit molecular mechanisms and chemical reactions within their cells, distinguishing them from non-living things. The presence of continuous molecular reactions is a major proof of life.

• Molecular Mechanisms: Organic molecules undergo reactions in living cells.
• Cellular Basis: All living things are made of cells, which are composed of atoms and molecules.
• Comparison: Non-living…

Life Processes

Life processes are the essential functions carried out by living organisms to maintain life. These include nutrition, respiration, transportation, and excretion. Each process is vital for growth, energy production, material transfer, and waste elimination.

Characteristics of Living Organisms

Living organisms exhibit molecular mechanisms and chemical reactions within their cells, distinguishing them from non-living things. The presence of continuous molecular reactions is a major proof of life.

• Molecular Mechanisms: Organic molecules undergo reactions in living cells.
• Cellular Basis: All living things are made of cells, which are composed of atoms and molecules.
• Comparison: Non-living objects may contain atoms and molecules but lack ongoing molecular reactions.

Nutrition: Types and Mechanisms

Nutrition is the process by which organisms take in food and utilize it for growth, energy, and repair. It is not just food intake but also its utilization.

• Purpose: Food is required for growth, energy, and repair mechanisms.
• Definition: The process of taking food into the body and utilizing it is called nutrition.

Types of Nutrition

Organisms are classified based on how they obtain food:

• Autotrophic Nutrition: Organisms prepare their own food (e.g., green plants, blue-green algae/cyanobacteria).
  • Key pigment: Chlorophyll enables food synthesis.
• Heterotrophic Nutrition: Organisms depend on others for food.
  • Types:
    • Holozoic: Whole food is ingested and digested (e.g., humans, amoeba).
    • Saprophytic: Feed on dead and decaying matter (e.g., fungi, mushrooms).
    • Parasitic: Depend on live hosts for food (e.g., lice, ticks, Plasmodium, Cuscuta plant).

Autotrophic Nutrition and Photosynthesis

Autotrophs synthesize food using inorganic substances, mainly through photosynthesis. This process occurs in green plants due to chlorophyll.

• Photosynthesis Definition: The process of making food by green plants with chlorophyll using sunlight, carbon dioxide, and water.
• Key Points:
  • Chlorophyll is the kitchen of the plant cell.
  • Light energy is converted to chemical energy.

Photosynthesis Equation

The transcript provides the photosynthesis formula:

• Raw Materials: Carbon dioxide, water, sunlight.
• Main Product: Glucose ($C_6H_{12}O_6$).
• By-product: Oxygen.

Leaf Structure and Photosynthesis

Photosynthesis occurs in the leaf, specifically in mesophyll cells containing chloroplasts.

• Leaf Layers: Outer epidermal layer, inner mesophyll (palisade and spongy cells).
• Chloroplast Structure: Contains thylakoids (coin-like), grana (group of thylakoids), and stroma (space between grana).
• Stomata: Guard cells and subsidiary cells regulate gaseous exchange and transpiration.

Experiments Related to Photosynthesis

Two key experiments are described to prove requirements for photosynthesis:

Variegated Leaf Experiment

This experiment demonstrates the necessity of chlorophyll for photosynthesis.

• Procedure:
  1. Select a plant with variegated leaves (green and yellow parts).
  2. Destarch the plant by keeping it in darkness for 24–48 hours.
  3. Expose to sunlight for 4–6 hours.
  4. Boil leaf in water, then in alcohol to remove chlorophyll.
  5. Add iodine solution to test for starch.
• Observation: Green parts turn blue-black (starch present), yellow parts show no color change (no starch).
• Conclusion: Chlorophyll is necessary for photosynthesis.

Bell Jar Experiment

This experiment proves carbon dioxide is essential for photosynthesis.

• Setup:
  • Two bell jars, each with a potted plant.
  • In one jar, place potassium hydroxide (KOH) to absorb CO$_2$.
  • The other jar serves as control (no KOH).
• Procedure:
  1. Destarch plants.
  2. Arrange setup and expose to sunlight.
  3. Test leaves for starch with iodine.
• Observation: Only the plant with CO$_2$ available forms starch (blue-black color).
• Conclusion: CO$_2$ is essential for photosynthesis.

Heterotrophic Nutrition in Detail

Heterotrophs depend on other organisms for food. Three main types are described:

• Holozoic Nutrition: Involves ingestion, digestion, absorption, assimilation, and egestion.
  • Amoeba: Uses pseudopodia to engulf food, forms food vacuole, digests, absorbs, and ejects waste.
  • Humans: Food is ingested via mouth, mixed with saliva (salivary amylase), moves through esophagus (peristaltic movement), digested in stomach (HCl, pepsin), and absorbed in small intestine (villi).
• Saprophytic Nutrition: Fungi feed on dead matter.
• Parasitic Nutrition: Parasites feed on live hosts (e.g., lice, ticks, Plasmodium, Cuscuta).

Human Digestive System

The digestive system involves several organs and processes for food breakdown and absorption.

• Mouth: Grinding, mixing with saliva (salivary amylase breaks down starch).
• Esophagus: Peristaltic movement pushes food to stomach.
• Stomach: HCl creates acidic medium, activates pepsin for protein digestion, mucus protects stomach lining.
• Small Intestine: Complete digestion and absorption occur. Bile from liver emulsifies fats, pancreatic juice contains amylase (carbohydrates), trypsin (proteins), lipase (fats). Villi increase surface area for absorption.
• Large Intestine: Water reabsorption, waste moves to rectum and anus for egestion.

Respiration: Types and Pathways

Respiration is the biochemical process of energy release from food. It differs from breathing, which is only the physical intake and expulsion of gases.

• Definition: Breakdown of glucose to release energy.
• Types:
  • Aerobic Respiration: Occurs in presence of oxygen; glucose breaks down to pyruvate (glycolysis in cytoplasm), then further in mitochondria to CO$_2$, water, and ATP (more energy released).
  • Anaerobic Respiration: Occurs in absence of oxygen; glucose converts to lactic acid (in muscle cells during vigorous exercise) or ethanol (in yeast, fermentation). Less energy released.

Key Points

• ATP: Adenosine triphosphate is the energy currency of the cell.
• Glycolysis: Glucose (6-carbon) breaks down to pyruvate (3-carbon) in cytoplasm.
• Fermentation: In yeast, glucose converts to ethanol (alcohol).

Human Respiratory System

The pathway for air in humans involves several structures:

• Nasal Cavity: Filters dust, regulates temperature.
• Pharynx: Common pathway for food and air.
• Larynx: Voice box.
• Trachea: Windpipe.
• Bronchi and Bronchioles: Branches leading to lungs.
• Alveoli: Balloon-like sacs for gaseous exchange; thin walls, large surface area, rich in blood capillaries.
• Epiglottis: Separates food and air pathways.

Transportation in Humans and Plants

Transportation involves the movement of materials like oxygen, nutrients, hormones, and waste.

Human Circulatory System

• Heart: Pumping machine, size of a fist, four chambers (two atria, two ventricles).
• Double Circulation: Blood enters heart twice—once as deoxygenated, once as oxygenated.
  • Pulmonary Circulation: Heart to lungs and back.
  • Systemic Circulation: Heart to body and back.
• Valves: Tricuspid (right), bicuspid (left) prevent backflow.
• Blood Vessels: Arteries (carry oxygenated blood away from heart), veins (carry deoxygenated blood to heart), capillaries (connect arteries and veins).
• Exceptions: Pulmonary artery carries deoxygenated blood; pulmonary vein carries oxygenated blood.
• Blood Pressure: Normal is 120/80 mmHg, measured by sphygmomanometer.

Plant Transportation

• Vascular Bundle: Composed of xylem and phloem.
  • Xylem: Transports water and minerals (unidirectional, root to shoot).
    • Mechanisms: Root pressure (short plants), transpiration pull (tall plants).
  • Phloem: Transports food (bidirectional, process called translocation).

Excretion: Human and Plant Mechanisms

Excretion is the process of removing waste materials from the body.

Human Excretory System

• Organs: Pair of kidneys, ureters, urinary bladder, urethra.
• Kidney Structure: Contains nephrons (structural and functional unit).
  • Nephron Parts: Glomerulus, Bowman's capsule (Malpighian body), proximal convoluted tubule (PCT), loop of Henle, distal convoluted tubule (DCT), collecting duct.
• Urine Formation Steps:
  1. Ultrafiltration: Occurs in glomerulus; blood filtered, primary urine formed.
  2. Selective Reabsorption: Useful substances reabsorbed in PCT, loop of Henle, DCT.
  3. Tubular Secretion: Impurities secreted into urine.
  4. Concentration: Water reabsorbed, urine concentrated; regulated by ADH (vasopressin).
• Urine Pathway: Kidneys → ureters → urinary bladder (temporary storage) → urethra (excretion).
• Dialysis: Artificial kidney process for patients with kidney failure; impure blood purified by diffusion.

Plant Excretion

• Mechanisms: Not detailed in transcript.

Blood Components and Functions

Blood consists of three main components, each with specific functions.

• Red Blood Cells (RBCs): Contain hemoglobin, carry oxygen.
• White Blood Cells (WBCs): Provide immunity.
• Platelets: Help in blood clotting (coagulation).

Key Exam Points and Diagrams

• Photosynthesis equation and leaf structure diagrams are essential.

• Variegated leaf and bell jar experiments are important for 8-mark questions.

• Digestive system, heart, nephron diagrams must be practiced for exams.

• Peristaltic movement, double circulation, and blood pressure values are frequently asked.

• Exceptions in blood vessels (pulmonary artery/vein) should be noted.

• Dialysis and kidney transplantation are discussed as solutions for kidney failure.

• Practice all diagrams and revise notes for full marks.