Overview
This lecture covers life processes in living organisms, including nutrition, respiration, transport, and excretion, with examples from plants and animals, especially humans.
Life Processes and Criteria for Life
- Living organisms exhibit movement, growth, metabolism, and molecular-level activity.
- Life processes include nutrition, respiration, transport of materials, and excretion.
- Maintenance of molecular order in cells requires continuous energy input and repair.
- Specialized tissues and transport systems are needed in multicellular organisms for efficient distribution of food, oxygen, and removal of waste.
Nutrition
- Nutrition is obtaining energy and raw materials from outside for maintenance and growth.
- Autotrophs (e.g., green plants) use simple inorganic substances (COâ‚‚, Hâ‚‚O) and energy from sunlight to make food via photosynthesis.
- Heterotrophs (e.g., animals, fungi) depend on complex organic substances made by other organisms.
- Enzymes break down food to simpler molecules for absorption.
Photosynthesis
- Essential requirements: sunlight, chlorophyll, COâ‚‚, and water.
- Three major events: absorption of light by chlorophyll, conversion of light energy to chemical energy and splitting of water, reduction of COâ‚‚ to carbohydrates.
- Stomata on leaves facilitate gas exchange; guard cells control stomatal opening and closing.
Nutrition in Humans
- The digestive tract processes food mechanically and chemically.
- Enzymes such as salivary amylase, pepsin, trypsin, and lipase help break down carbohydrates, proteins, and fats.
- Villi in the small intestine absorb digested food into the bloodstream.
Respiration
- Respiration breaks down glucose to release energy (ATP).
- Aerobic respiration (with oxygen) yields COâ‚‚, water, and more energy.
- Anaerobic respiration (without oxygen) produces less energy and end-products like ethanol or lactic acid.
- In humans, gas exchange occurs in alveoli of lungs, aided by haemoglobin for oxygen transport.
Transportation
- In humans, the circulatory system (heart, blood, blood vessels) transports nutrients, gases, and waste.
- The heart separates oxygen-rich and oxygen-poor blood for efficient supply.
- Blood pressure is the force exerted by blood on vessel walls.
- Lymph transports tissue fluid, waste, and digested fats.
Plant Transport Systems
- Xylem transports water and minerals from roots to leaves via transpiration and root pressure.
- Phloem transports products of photosynthesis (like sucrose) from leaves to other plant parts by translocation, which requires energy.
Excretion
- Excretion removes harmful metabolic wastes.
- In humans, nephrons in the kidneys filter blood to form urine, reabsorbing useful substances.
- Plants excrete wastes by storing them in vacuoles, leaves, as resins/gums, or releasing them into the soil.
Key Terms & Definitions
- Autotroph — Organism making its own food from inorganic substances using sunlight.
- Heterotroph — Organism getting food from complex organic substances.
- Photosynthesis — Process by which plants convert CO₂ and water to carbohydrates using sunlight.
- Enzyme — Biological catalyst speeding up chemical reactions.
- ATP (Adenosine Triphosphate) — Main energy currency in cells.
- Haemoglobin — Blood pigment transporting oxygen.
- Xylem — Plant tissue transporting water/minerals.
- Phloem — Plant tissue transporting food.
- Nephron — Kidney unit filtering blood and forming urine.
Action Items / Next Steps
- Review activities and experiments mentioned (e.g., starch test in leaves, effect of saliva on starch, lime water test for COâ‚‚).
- Study diagrams of the human digestive and respiratory systems, heart, nephron, and plant tissues (xylem/phloem).
- Answer textbook exercise questions for practice.