Life Processes Overview

Overview

This lecture covers the "Life Processes" chapter in biology, focusing on nutrition, respiration, transportation, and excretion in plants and animals. It explains definitions, examples, processes, and key points important for board exams, with detailed explanations and diagrams.

Life Processes: Introduction

Life processes are essential functions that living organisms perform to sustain life on Earth.
Main life processes: nutrition, respiration, transportation, and excretion.
These processes are necessary for survival, growth, and maintenance of the body.
All living organisms, from unicellular (e.g., amoeba) to multicellular (e.g., humans, plants), perform these processes.
The chapter is based on NCERT and is relevant for all boards (CBSE, SSC, UP Board, etc.).

Nutrition

Nutrition is the process by which living organisms obtain and utilize food for energy, growth, and repair.
Importance of nutrition:
- Provides energy for all activities.
- Supports growth and development.
- Repairs damaged tissues.
Types of nutrition:
- Autotrophic nutrition: Organisms make their own food (e.g., plants).
  - Photosynthetic autotrophic nutrition: Plants use sunlight, CO₂, water, and chlorophyll to make food through photosynthesis.
    - Photosynthesis reaction:
      6CO₂ + 6H₂O → C₆H₁₂O₆ + 6O₂
    - Requirements: carbon dioxide (from air via stomata), water (from soil via roots), sunlight, and chlorophyll (green pigment in leaves).
    - Plants store glucose as starch.
    - Photosynthesis occurs in three steps: absorption of light by chlorophyll, conversion of light energy to chemical energy (splitting water into hydrogen and oxygen), and reduction of CO₂ to carbohydrates.
    - Stomata: tiny pores on leaves for gas exchange and transpiration.
    - In desert plants, stomata open at night to reduce water loss.
  - Chemosynthetic autotrophic nutrition: Some bacteria (e.g., sulfur bacteria) use chemicals (not sunlight) to make food.
- Heterotrophic nutrition: Organisms depend on others for food (e.g., animals, fungi).
  - Holozoic nutrition: Ingest solid food, digest, and absorb (e.g., humans, animals).
    - Types: herbivores (plant-eaters), carnivores (meat-eaters), omnivores (eat both).
  - Saprotrophic nutrition: Organisms (e.g., fungi, bacteria) digest food outside their body and absorb nutrients.
  - Parasitic nutrition: Organisms (e.g., lice, leeches, Cuscuta plant) live on or inside another organism and obtain food from the host.
Nutrition in unicellular organisms (e.g., amoeba) involves five steps: ingestion, digestion, absorption, assimilation, and egestion.

Human Nutrition & Digestion

The human digestive system consists of the alimentary canal and associated organs.
- Alimentary canal: mouth (buccal cavity), esophagus, stomach, small intestine, large intestine, anus.
- Associated organs: liver, pancreas, salivary glands.
Digestion process:
- Mouth: Teeth break down food; saliva (contains salivary amylase) converts starch to maltose.
- Esophagus: Moves food to stomach by peristalsis (wave-like muscle contractions).
- Stomach: Secretes hydrochloric acid (kills bacteria, provides acidic medium), pepsin (digests proteins), and mucus (protects stomach lining).
- Small intestine: Receives bile (from liver, stored in gall bladder—emulsifies fats, neutralizes acid) and pancreatic juices (trypsin for proteins, lipase for fats, amylase for carbohydrates). Intestinal juices further digest food. Villi (finger-like projections) absorb nutrients into blood.
- Large intestine: Absorbs water, forms feces from undigested food.
Five steps of nutrition in humans: ingestion, digestion, absorption, assimilation (distribution and use of absorbed nutrients), and egestion (removal of undigested waste).
Herbivores have a longer small intestine than carnivores to digest cellulose from plants.

Respiration

Respiration is the process of breaking down food (mainly glucose) to release energy (ATP) for cellular activities.
Types of respiration:
- Aerobic respiration: Occurs in the presence of oxygen; glucose is broken down into CO₂, H₂O, and ATP (energy).
  - Equation: Glucose + O₂ → CO₂ + H₂O + ATP
  - Occurs in mitochondria.
- Anaerobic respiration: Occurs in the absence or low amount of oxygen; glucose is partially broken down, producing less energy.
  - In yeast: glucose → ethanol + CO₂ + ATP
  - In muscles (during heavy exercise): glucose → lactic acid + ATP (causes cramps).
Difference between breathing and respiration:
- Breathing: physical process of inhaling and exhaling air.
- Respiration: chemical process of breaking down food to release energy.
Gas exchange in humans:
- Air enters through the nasal cavity, passes through the larynx (voice box), trachea (windpipe), bronchi, bronchioles, and reaches alveoli (tiny air sacs in lungs).
- In alveoli, oxygen diffuses into blood (binds to hemoglobin in RBCs), and carbon dioxide diffuses out to be exhaled.
- Double circulation ensures efficient oxygen supply and removal of CO₂.
In fish, respiration occurs through gills, which extract oxygen from water.

Transportation

Transportation is the movement of substances (nutrients, gases, wastes) within the body.
Circulatory system in humans:
- Components: heart (pumps blood), blood vessels (arteries, veins, capillaries), blood.
- Blood:
  - Plasma: liquid part.
  - RBCs (red blood cells): contain hemoglobin, transport oxygen.
  - WBCs (white blood cells): provide immunity.
  - Platelets: help in blood clotting.
  - Functions: transport oxygen, nutrients, hormones; maintain temperature and pH; remove wastes.
- Blood vessels:
  - Arteries: carry blood away from heart (usually oxygenated, except pulmonary artery).
  - Veins: carry blood to heart (usually deoxygenated, except pulmonary vein).
  - Capillaries: connect arteries and veins; site of exchange of substances.
  - Arteries have thick walls (high pressure); veins have valves (prevent backflow).
- Heart:
  - Four chambers: right atrium, right ventricle, left atrium, left ventricle.
  - Double circulation: blood passes through heart twice in one cycle (systemic and pulmonary circuits).
  - Oxygenated blood from lungs enters left atrium, pumped to body; deoxygenated blood returns to right atrium, pumped to lungs for oxygenation.
  - Valves prevent backflow of blood.
- Lymphatic system:
  - Lymph: colorless fluid, part of immune system.
  - Lymph vessels and nodes: transport lymph, maintain fluid balance, help in fat absorption, and provide immunity.

Transportation in Plants

Plants have two main transport tissues:
- Xylem: transports water and minerals from roots to leaves (unidirectional).
  - Composed mainly of dead cells.
  - Water moves upward due to transpiration pull (loss of water vapor from leaves).
- Phloem: transports food (glucose) from leaves to other parts (bidirectional).
  - Composed of living cells.
  - Translocation: movement of food up and down the plant.
Functions of transportation in plants:
- Absorption and movement of water and minerals.
- Distribution of food.
- Regulation of temperature (transpiration).
- Removal of excess water.
Differences between xylem and phloem:
- Xylem: unidirectional, dead cells, transports water/minerals.
- Phloem: bidirectional, living cells, transports food.

Excretion

Excretion is the removal of metabolic (mainly nitrogenous) wastes from the body.
Excretory system in humans:
- Main organs: kidneys, ureters, urinary bladder, urethra.
- Kidneys: filter blood, remove wastes, regulate water and salt balance, produce urine.
  - Functional unit: nephron.
    - Steps in urine formation:
      1. Glomerular filtration: blood filtered in Bowman's capsule; wastes, water, and small molecules enter nephron.
      2. Selective reabsorption: useful substances (glucose, amino acids, water) reabsorbed into blood.
      3. Tubular secretion: additional wastes secreted into nephron.
    - Urine passes from nephron to collecting duct, then to ureter, bladder, and out via urethra.
- Dialysis: artificial process to remove wastes from blood if kidneys fail (acts as an artificial kidney).
Excretion in plants:
- Remove excess water by transpiration.
- Release oxygen and CO₂ via stomata.
- Store waste in vacuoles, or secrete as resins, gums, latex.

Key Terms & Definitions

Autotrophic nutrition: Organisms make their own food (e.g., plants).
Heterotrophic nutrition: Organisms depend on others for food (e.g., animals).
Photosynthesis: Process of making food using sunlight, CO₂, and water.
Peristalsis: Wave-like muscle contractions in the alimentary canal.
Villi: Finger-like projections in the small intestine for absorption.
ATP (Adenosine Triphosphate): Energy currency of the cell.
Hemoglobin: Protein in RBCs that carries oxygen.
Double circulation: Blood flows twice through the heart per cycle.
Nephron: Functional unit of the kidney for filtration.
Dialysis: Artificial process to remove waste from blood.
Stomata: Small pores on leaves for gas exchange and transpiration.
Transpiration: Loss of water vapor from plant leaves.
Translocation: Movement of food in plants via phloem.
Assimilation: Utilization of absorbed nutrients for growth and repair.

Action Items / Next Steps

Revise and practice diagrams of digestive, respiratory, circulatory, and excretory systems (label all parts).
Practice past exam and sample questions on all life processes.
Review the NCERT textbook line-by-line for this chapter, focusing on definitions and diagrams.
Memorize key differences (e.g., xylem vs. phloem, arteries vs. veins, aerobic vs. anaerobic respiration).
Prepare for the next lecture on "Control and Coordination."
Join the class Telegram group for extra questions and updates.
Share and discuss concepts with classmates for better understanding.