Life Processes

  • Understanding Life Processes

    • Identifying living vs non-living:

    • Examples: dog running vs cow chewing, etc.

    • Criteria for life: breathing, growth, and movement.

    • Presence of molecular movements essential for life.

    • Controversy with Viruses:

    • Lack of molecular movement when uninfected raises questions on their life status.

  • Life Processes

    • Maintenance processes are vital even in inactivity (e.g. while asleep).

    • Energy needed for these processes comes from nutrition.

    • Nutritional processes: delivery of external energy (food) for maintenance and growth.

    • Most food sources are carbon-based due to the reliance of life on carbon compounds.

  • Energy Transfer Processes:

    • Energy from food is processed through chemical reactions, usually oxidation (oxidising-reducing reactions).

    • Oxygen's role in energy generation via respiration.

5.1 Nutrition

  • Nutrition Defined:

    • Required for energy, growth, and maintenance of body order, even during inactivity.

    • Types of Nutrition:

    • Autotrophic Nutrition:

      • Organisms (e.g. plants, bacteria) obtain energy from inorganic substances (CO2 + water) via photosynthesis.

      • Carbohydrates produced serve as energy storage (e.g. starch).

    • Heterotrophic Nutrition:

      • Organisms (e.g. animals, fungi) require complex organic materials and depend directly or indirectly on autotrophs.

5.2 The Process of Photosynthesis

  • Photosynthesis Steps:

    • Absorption of light by chlorophyll.

    • Conversion of light energy into chemical energy.

    • Splitting of water molecules and reduction of CO2 to carbohydrates.

    • Example activities:

    • Starch test to identify photosynthesis occurrence in leaves.

    • Plant Nutrient Needs: Water absorption from soil; Nitrogen and other minerals essential for growth.

  • Heterotrophic Nutrition Examples:

    • Organisms that break down food externally (e.g. fungi) vs those that ingest and digest internally (e.g. humans).

5.3 Respiration

  • Respiration Types:

    • Aerobic Respiration:

    • Requires oxygen; breaks down glucose completely for maximum energy (ATP production).

    • Anaerobic Respiration:

    • No oxygen; releases less energy (e.g. fermentation).

5.4 Transportation

  • Human Circulatory System:

    • Components: Heart, blood, blood vessels, carrying oxygen, nutrients, and waste products.

    • Double circulation in mammals allows efficient oxygenation and waste removal.

    • Plant Transport Processes:

    • Xylem: moves water and minerals from roots to leaves.

    • Phloem: moves nutrients (sugars) produced in leaves to other plant parts.

  • System Components:

    • Xylem: Water conducting.

    • Phloem: Nutrient conducting.

    • Both systems highlight adaptations for efficient transport given plant structure.

5.5 Excretion

  • Excretion Defined:

    • Removal of harmful metabolic waste (e.g. nitrogenous wastes).

    • Human Excretory System:

    • Kidneys filter blood, producing urine. Functional unit: nephron.

    • Plant Excretion:

    • Excess oxygen, water loss via transpiration; waste stored in cells or lost with leaves.

  • Key Learnings:

    • Life requires processes for maintaining order through nutrition, respiration, transport, and excretion.

    • Autotrophic and heterotrophic methods define how organisms obtain and use energy.

    • Circulatory and excretory systems play crucial roles in maintaining homeostasis and overall health.