Chapter 5: Life Processes
Chapter learning goals: Understand the core concepts, explain key processes, interpret diagrams and apply the ideas to board-style questions.
Read each concept, mark definitions and formulae, practise the worked examples, then attempt the revision questions without looking at the answers.
1. What are life processes?
Living organisms need maintenance activities to stay alive. Nutrition supplies materials and energy; respiration releases usable energy from food; transportation moves substances; excretion removes metabolic wastes. Movement or growth alone is not enough to define life. These processes operate continuously, even when an organism appears inactive.
2. Nutrition: autotrophic and heterotrophic
Autotrophs make organic food from inorganic substances; green plants use photosynthesis. Equation: 6CO₂ + 6H₂O —light/chlorophyll→ C₆H₁₂O₆ + 6O₂. Chlorophyll captures light, stomata admit CO₂, roots absorb water, and sunlight powers conversion. Heterotrophs obtain food from other organisms. Modes include holozoic (ingestion, digestion, absorption, assimilation, egestion), saprophytic and parasitic.
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