1. What Are Life Processes?
Living organisms are highly organised systems. Their internal organisation is continuously affected by the surroundings, so they need processes that maintain, repair and operate the body. These essential maintenance functions are called life processes.
2. Nutrition
Nutrition is the process by which organisms obtain food and use it for energy, growth, repair and maintenance.
2.1 Autotrophic Nutrition
Green plants prepare their own food from carbon dioxide and water using sunlight and chlorophyll. This is photosynthesis.
Raw Materials and Their Sources
| Requirement | Source / role |
|---|---|
| Carbon dioxide | Enters leaves mainly through stomata. |
| Water | Absorbed by roots and transported through xylem. |
| Sunlight | Provides energy for photosynthesis. |
| Chlorophyll | Pigment that captures light energy. |
Stomata
Stomata are tiny pores, mainly on leaf surfaces. Their opening and closing regulate gaseous exchange and water loss. Guard cells control the stomatal pore.
2.2 Heterotrophic Nutrition
Organisms that cannot synthesise their own food and depend directly or indirectly on other organisms are heterotrophs.
2.3 Nutrition in Amoeba
Amoeba takes in food using temporary finger-like extensions called pseudopodia. Food is enclosed in a food vacuole, digested, absorbed and assimilated; undigested material is expelled.
2.4 Human Digestive System
| Part | Major function |
|---|---|
| Mouth | Chewing; saliva begins digestion of starch. |
| Oesophagus | Moves food to stomach by peristalsis. |
| Stomach | HCl provides acidic medium; pepsin begins protein digestion; mucus protects lining. |
| Small intestine | Receives bile and pancreatic juice; completes digestion; absorbs nutrients through villi. |
| Large intestine | Absorbs water and helps form faeces. |
| Rectum and anus | Temporary storage and elimination of faeces. |
Digestive Glands
Liver: produces bile, which helps in emulsification of fats and provides an alkaline medium. Pancreas: secretes digestive enzymes. Salivary glands: secrete saliva containing salivary amylase.
3. Respiration
Respiration is the process of breaking down food to release energy. The released energy is captured in a usable form, mainly ATP.
3.1 Breakdown of Glucose
| Condition | Pathway / products |
|---|---|
| With sufficient oxygen | Pyruvate → carbon dioxide + water + large amount of energy. |
| Low oxygen in muscles | Pyruvate → lactic acid + some energy; may cause cramps. |
| Yeast / absence of oxygen | Pyruvate → ethanol + carbon dioxide + some energy. |
3.2 ATP
ATP acts as an energy currency of the cell. Energy released during respiration is used to form ATP, which can power cellular activities.
3.3 Human Respiratory System
Alveoli are tiny air sacs where gaseous exchange occurs. They provide a large surface area and have thin, moist walls with a rich blood supply.
Breathing Mechanism
| Inhalation | Exhalation |
|---|---|
| Diaphragm contracts and flattens; ribs move up and out; chest cavity volume increases; air enters. | Diaphragm relaxes; ribs move down and in; chest cavity volume decreases; air is pushed out. |
Respiration in Plants
Plants exchange gases by diffusion. Leaves use stomata, stems have lenticels, and roots exchange gases with air spaces in soil.
4. Transportation
4.1 Transportation in Human Beings
The circulatory system consists mainly of the heart, blood and blood vessels.
Blood
| Component | Function |
|---|---|
| Plasma | Liquid medium carrying dissolved substances. |
| Red blood cells (RBCs) | Contain haemoglobin and transport oxygen. |
| White blood cells (WBCs) | Help defend the body against infection. |
| Platelets | Help in blood clotting. |
Heart and Double Circulation
The human heart has four chambers: right atrium, right ventricle, left atrium and left ventricle. Valves help prevent backflow.
Double circulation means blood passes through the heart twice during one complete cycle: pulmonary circulation between heart and lungs, and systemic circulation between heart and body.
Blood Vessels
| Arteries | Veins | Capillaries |
|---|---|---|
| Carry blood away from heart; generally thick, elastic walls. | Carry blood towards heart; valves prevent backflow. | Very thin vessels connecting arterioles and venules; exchange materials with tissues. |
Lymph
Lymph is a fluid involved in transport of substances and in returning excess tissue fluid to the blood. It also has roles in immunity and transport of absorbed fats from the intestine.
4.2 Transportation in Plants
Xylem transports water and minerals from roots to other parts. Phloem transports food from leaves to other parts of the plant.
5. Excretion
Excretion is the removal of metabolic wastes from an organism.
5.1 Excretion in Human Beings
Each kidney contains many filtering units called nephrons.
Urine Formation
- Filtration: Blood is filtered in the glomerulus and filtrate enters Bowman's capsule.
- Selective reabsorption: Useful substances and much of the water are reabsorbed according to the body's needs.
- Secretion / final processing: Additional wastes and ions are added to the filtrate, producing urine.
Dialysis
When kidneys cannot adequately filter blood, an artificial kidney may be used to remove wastes and excess fluid. This process is called dialysis.
Excretion in Plants
Plants remove wastes through diffusion, transpiration, storage in vacuoles, storage as gums and resins, and shedding of leaves or other parts. Oxygen and carbon dioxide can also leave through stomata and other openings depending on the process.
6. Important Comparisons
| Topic | Key distinction |
|---|---|
| Autotrophic vs heterotrophic nutrition | Autotrophs synthesise food; heterotrophs depend on other sources. |
| Aerobic vs anaerobic respiration | Aerobic respiration uses oxygen and generally releases more energy; anaerobic pathways operate without oxygen and release less energy. |
| Artery vs vein | Artery carries blood away from heart; vein carries blood towards heart. |
| Xylem vs phloem | Xylem mainly transports water/minerals; phloem transports food. |
| Breathing vs respiration | Breathing is physical movement of air; respiration is cellular chemical release of energy from food. |
| Filtration vs reabsorption | Filtration separates substances from blood into nephron; reabsorption returns useful substances to blood. |
7. Quick Revision Sheet
8. 30 Practice Questions
- Why are maintenance processes necessary for living organisms?
- Define life processes and name four major life processes studied in this chapter.
- What is autotrophic nutrition?
- Write the word equation for photosynthesis.
- What is the role of chlorophyll in photosynthesis?
- How do stomata help plants?
- Differentiate autotrophic and heterotrophic nutrition.
- Explain nutrition in Amoeba.
- What is the role of HCl in the stomach?
- Why is mucus present in the stomach?
- What is the function of bile in digestion?
- Why is the small intestine well suited for absorption?
- Define respiration.
- Why is ATP called the energy currency of the cell?
- What happens to pyruvate when oxygen is insufficient in muscle cells?
- Why do muscles sometimes develop cramps after strenuous exercise?
- State two features of alveoli that make gaseous exchange efficient.
- Describe the mechanism of inhalation and exhalation.
- Why do plants need to exchange gases?
- Name the components of the human circulatory system.
- Differentiate arteries and veins.
- Explain double circulation in humans.
- What is the function of haemoglobin?
- What is lymph and why is it important?
- Differentiate xylem and phloem.
- What is transpiration and how does it help plants?
- Define excretion.
- Describe the three major stages involved in urine formation.
- What is a nephron?
- Explain dialysis and state when it may be required.
9. CBSE PYQ / PYQ-Based Practice
These are exam-style and PYQ-based questions designed around recurring CBSE concepts and competency patterns.
- A student covers part of a leaf with black paper and exposes the plant to sunlight. Explain the purpose of this experiment and the expected observation.
- Why does the rate of breathing increase during vigorous physical activity?
- Explain why the separation of oxygenated and deoxygenated blood is useful in humans.
- Draw and label a nephron and explain how urine is formed.
- Explain how water is transported from roots to leaves in tall plants.
- Why is diffusion insufficient to meet the oxygen requirements of large multicellular organisms?
- Compare aerobic respiration and anaerobic respiration on the basis of oxygen requirement, end products and energy release.
- Explain the role of villi in the small intestine.
- Why are arteries thick-walled whereas veins contain valves?
- Explain how transpiration contributes to water movement in plants.
- Describe the pathway followed by food through the human alimentary canal.
- What would happen if stomata remain closed for a long period?
- Explain why the left ventricle has a thicker muscular wall than the right ventricle.
- A person has damaged nephrons. Which major function of the kidney would be affected? Explain.
- How does the structure of alveoli support efficient gaseous exchange?
- Why is the small intestine longer and more highly folded than the large intestine?
- Explain the role of blood in transportation of oxygen, nutrients and wastes.
- How do plants remove metabolic wastes despite having no specialised excretory organs?
- What is translocation? Why can it occur in different directions in a plant?
- Explain the significance of double circulation in humans.