Life Processes

Life processes are the basic functions performed by living organisms to maintain life, such as nutrition, respiration, transportation, and excretion. These processes ensure the survival and proper functioning of organisms by providing energy, removing waste, and facilitating growth. Without these processes, organisms would not be able to sustain life.

Autotrophic nutrition involves organisms producing their own food using sunlight, water, and carbon dioxide, like plants through photosynthesis. Heterotrophic nutrition involves organisms consuming other organisms or organic matter for food, like animals and fungi. Autotrophs are producers, while heterotrophs are consumers in the food chain.

Photosynthesis occurs in the chloroplasts of plant cells, where chlorophyll absorbs sunlight. The process converts carbon dioxide and water into glucose and oxygen using light energy. This glucose is used for energy or stored as starch, while oxygen is released into the atmosphere.

Chlorophyll is a green pigment found in chloroplasts that absorbs sunlight, which is essential for photosynthesis. It captures light energy and converts it into chemical energy to synthesize glucose from carbon dioxide and water. Without chlorophyll, plants cannot perform photosynthesis.

Digestion in humans starts in the mouth where saliva breaks down starch. Food then moves to the stomach, where gastric juices digest proteins. In the small intestine, bile and pancreatic juices break down fats, and nutrients are absorbed into the bloodstream.

The small intestine is where most digestion and nutrient absorption occur. It receives secretions from the liver and pancreas to break down fats, proteins, and carbohydrates. Villi in the small intestine increase surface area for efficient absorption of nutrients into the blood.

Aerobic respiration occurs in the presence of oxygen, producing carbon dioxide, water, and a large amount of energy (ATP). Anaerobic respiration occurs without oxygen, producing lactic acid in muscles or ethanol and carbon dioxide in yeast, yielding less energy.

Haemoglobin in red blood cells binds with oxygen to form oxyhaemoglobin, transporting oxygen from the lungs to tissues. It also carries some carbon dioxide back to the lungs. A deficiency in haemoglobin can lead to fatigue and anemia due to reduced oxygen supply.

Double circulation involves two pathways: pulmonary circulation (heart to lungs and back) and systemic circulation (heart to body and back). This ensures oxygenated and deoxygenated blood do not mix, providing efficient oxygen supply to tissues and removing carbon dioxide.

The human circulatory system consists of the heart, blood vessels (arteries, veins, capillaries), and blood. The heart pumps blood, arteries carry oxygenated blood, veins carry deoxygenated blood, and capillaries facilitate exchange of materials between blood and tissues.

Plants transport water and minerals from roots to leaves through xylem vessels. Transpiration pull and root pressure help in the upward movement of water. Minerals are absorbed by roots and transported along with water to various plant parts.

Transpiration is the loss of water vapour from plant leaves through stomata. It creates a suction pull that helps in the upward movement of water and minerals from roots. It also cools the plant and maintains turgidity in cells.

Food is transported in plants through phloem via translocation. Sugars produced in leaves are converted into sucrose and transported to other parts like roots, fruits, and seeds. This process requires energy and occurs in both upward and downward directions.

Plants excrete oxygen as a by-product of photosynthesis. Other waste products include resins, gums, and tannins stored in leaves, bark, or vacuoles. Some wastes are excreted into the soil or shed with falling leaves.

Nephrons are the filtering units of kidneys, consisting of a glomerulus and Bowman’s capsule for blood filtration. They reabsorb useful substances like glucose and water, and excrete waste as urine. Nephrons maintain the body’s fluid and electrolyte balance.

Urine is formed in kidneys through filtration, reabsorption, and secretion. Blood is filtered in glomeruli, and useful substances are reabsorbed in tubules. Waste products like urea and excess water form urine, which is stored in the bladder before excretion.

The excretory system removes toxic nitrogenous wastes like urea and uric acid from the body. It regulates water, salt, and pH balance, maintaining homeostasis. Without it, waste accumulation would poison the body and disrupt cellular functions.

Aerobic respiration uses oxygen, produces more energy (36-38 ATP), and yields CO2 and water. Anaerobic respiration occurs without oxygen, produces less energy (2 ATP), and results in lactic acid or ethanol. Aerobic is more efficient but requires continuous oxygen supply.

The small intestine is long and coiled to increase surface area for maximum nutrient absorption. Its length ensures food stays longer for complete digestion. Villi and microvilli further enhance absorption efficiency by providing a large contact area.

Fermentation is anaerobic respiration where yeast converts glucose into ethanol and carbon dioxide. It releases energy and is used in baking (CO2 makes dough rise) and brewing (ethanol production). Lactic acid fermentation occurs in muscles during heavy exercise.

Guard cells control stomatal opening by changing shape due to water flow. When water enters, they swell and open stomata for gas exchange. When water exits, they shrink and close stomata to prevent water loss, especially in dry conditions.

Bile, produced by the liver, emulsifies fats into smaller droplets for easier digestion by lipases. It neutralizes stomach acid in the small intestine, creating an alkaline environment for enzyme action. Bile also helps in the absorption of fat-soluble vitamins.

Herbivores have a longer small intestine to digest cellulose from plant matter, which is harder to break down. The extended length allows more time for microbial fermentation and nutrient absorption. Carnivores digest meat faster, needing a shorter intestine.

Alveoli have thin walls (one-cell thick) for easy gas diffusion. A large surface area and moist lining enhance oxygen and CO2 exchange. Surrounding capillaries ensure efficient transport of gases between lungs and bloodstream.

Urine production is regulated by hormones like ADH, which controls water reabsorption in kidneys. More ADH reduces urine volume by retaining water, while less ADH increases urine output. This maintains the body’s water and salt balance.

Xylem transports water and minerals upwards from roots to leaves, composed of dead cells, and provides structural support. Phloem transports food (sugars) bidirectionally, made of living cells, and relies on energy for active transport. Both are vascular tissues but serve different functions.