Life Processes: Nutrition, Respiration, Transportation & Excretion

Chapter 5: Life Processes

Introduction

Life processes are the basic functions performed by living organisms for survival and body maintenance. These include nutrition, respiration, transportation, and excretion.

Nutrition

There are two modes of nutrition: autotrophic and heterotrophic.

Autotrophic Nutrition (Photosynthesis)

Photosynthesis is the process by which green plants synthesize their own food using carbon dioxide (CO₂) and water (H₂O) in the presence of chlorophyll and sunlight.

Raw Materials for Photosynthesis: Carbon dioxide and water.

Site of Photosynthesis: Chloroplasts in the leaves. Chloroplasts contain a green pigment called chlorophyll.

Main Events of Photosynthesis:

• Absorption of light energy by chlorophyll.
• Conversion of light energy to chemical energy and splitting of water molecules into hydrogen and oxygen.
• Reduction of CO₂ to form carbohydrates.

Stomata: Tiny pores on the surface of leaves that facilitate gas exchange (including CO₂ intake and O₂ release) and transpiration (water loss).

The opening and closing of stomata are regulated by guard cells.

Heterotrophic Nutrition

Heterotrophic nutrition involves obtaining food from other sources. It is classified into three types:

• Holozoic: Organisms ingest and digest food internally (e.g., Amoeba, animals).
• Saprophytic: Organisms obtain nutrients from dead and decaying organic matter (e.g., fungi).
• Parasitic: Organisms derive nourishment from a living host, harming it in the process (e.g., Cuscuta, ticks, and mites).

Nutrition in Amoeba: Amoeba uses temporary finger-like extensions called pseudopodia to engulf food particles, forming a food vacuole for digestion.

Human Digestive System: In humans, digestion begins in the mouth and is completed in the small intestine.

Respiration

Respiration is the process of producing energy in living organisms. There are two modes of respiration:

• Aerobic Respiration: Occurs in the presence of oxygen.
• Anaerobic Respiration: Occurs in the absence of oxygen.

Human Respiratory System: Involves the passage of air through the respiratory tract.

Mechanism of Breathing: Involves inhalation (taking in air) and exhalation (releasing air).

Oxygen Transport: In humans, oxygen is transported by hemoglobin, a respiratory pigment in red blood cells (RBCs) with a high affinity for oxygen.

Respiration in Different Organisms:

• Terrestrial organisms use atmospheric oxygen for respiration.
• Aquatic organisms use oxygen dissolved in water.
• Plants exchange gases through stomata in leaves, lenticels in stems, and the general surface of roots.

Transportation

Transportation in Humans

Circulatory System: Consists of blood, lymph, blood vessels (arteries, veins, and capillaries), and the heart.

Blood: A fluid connective tissue composed of plasma, RBCs, WBCs, and platelets.

Lymph: A yellowish fluid that escapes from blood capillaries into intercellular spaces, assisting in transportation and immune defense.

Double Circulation: Blood travels twice through the heart in one complete cycle. It includes:

• Pulmonary Circulation: Blood moves from the heart to the lungs and back.
• Systemic Circulation: Blood moves from the heart to the rest of the body and back.

Transportation in Plants

Xylem: Transports water and minerals from roots to other parts of the plant.

Phloem: Transports food (produced during photosynthesis) from leaves to other parts of the plant.

Transpiration: The loss of water vapor from plants, primarily through stomata.

Translocation: The movement of food from leaves (source) to other parts of the plant (sink).

Excretion

Excretion is the removal of harmful metabolic wastes from the body.

Human Excretory System: Includes a pair of kidneys, a urinary bladder, a pair of ureters, and a urethra.

Kidneys: Filter waste products (urea) from the blood. The nephron is the structural and functional unit of the kidney.

Urine Formation: Involves glomerular filtration, tubular reabsorption, and secretion.

Hemodialysis: An artificial process to purify blood for patients with kidney failure.

Photosynthesis Equation

The process of photosynthesis is commonly represented as:

6CO₂ + 6H₂O ---^{chlorophyll, sunlight}---> C₆H₁₂O₆ + 6O₂