Life Processes

Distinguishing Between Living and Non-living

• Living organisms exhibit movement, but not all movements are visible to the naked eye (e.g., molecular movement).
• Viruses are controversial in terms of being 'alive' due to their lack of molecular movement until they infect cells.

Why Molecular Movement is Essential

• Living organisms are organized structures (cells, tissues).
• Environmental effects can cause breakdown; hence, molecular movement is necessary for repair and maintenance.

5.1 What are Life Processes?

• Maintenance processes are required even during inactivity (e.g., sitting, sleeping).
• Energy, sourced externally as food, is essential for these processes.
• Processes involved include nutrition, respiration, transportation, and excretion.

5.2 Nutrition

Autotrophic Nutrition

• Autotrophs (e.g., green plants) use photosynthesis to convert carbon dioxide and water into carbohydrates, using sunlight and chlorophyll.
• Carbohydrates are stored as starch in plants, similar to glycogen in humans.

Photosynthesis Process

• Involves light absorption by chlorophyll, conversion to chemical energy, water splitting, and CO2 reduction to carbohydrates.
• Stomata play a key role in gaseous exchange.
• Guard cells regulate stomatal opening to minimize water loss during photosynthesis.

Heterotrophic Nutrition

• Heterotrophs depend on autotrophs for survival, utilizing complex substances broken down into simpler forms by enzymes.
• Various methods include saprophytic (e.g., fungi), holozoic (e.g., animals), and parasitic nutrition.

Human Digestive System

• Alimentary canal: mouth to anus, with specialized regions (e.g., stomach, intestines).
• Enzymes like salivary amylase aid in breaking down food into absorbable forms.
• Nutrients absorbed primarily in the small intestine via villi.

5.3 Respiration

• Cellular respiration converts glucose into energy (ATP).
• Aerobic respiration uses oxygen, takes place in mitochondria, and yields more energy.
• Anaerobic respiration occurs without oxygen, producing lactic acid or ethanol.

Human Respiratory System

• Involves lungs and alveoli for gas exchange.
• Oxygen is absorbed by hemoglobin, carbon dioxide transported dissolved in blood.

5.4 Transportation

In Human Beings

• Circulatory system: heart, blood, blood vessels.
• Double circulation prevents mixing of oxygenated and deoxygenated blood.
• Blood vessels: arteries (away from heart), veins (to heart), capillaries (exchange sites).
• Lymph system aids in transport of interstitial fluid.

In Plants

• Xylem transports water/minerals; phloem translocates food from leaves.
• Transpiration aids in upward movement of water.

5.5 Excretion

In Human Beings

• Excretory system: kidneys, ureters, bladder, urethra.
• Kidneys filter blood, forming urine.
• Nephrons are functional units where filtration and re-absorption occur.

In Plants

• Utilize storage and shedding (e.g., leaves) for waste disposal.
• Transpiration also helps in removing excess water.

Summary

• Life processes maintain homeostasis and energy flow.
• Differences exist between autotrophic and heterotrophic nutrition, aerobic and anaerobic respiration.
• Specialized structures in organisms ensure efficient transport and excretion.