19.1 Energy flow
- Syllabus
- 0610–2026–2027
- Topic
- 19.1
- Level
- —
Learning objectives
19.1.1Sun is the principal source of energy• State that the Sun is the principal source of energy input to biological systems19.1.2Flow of energy through living• Describe the flow of energy through living organisms, including light energy from the Sun and chemical energy in organisms, and its eventual transfer to the environment
Identify the principal energy source
The Sun is the principal source of energy input to biological systems.
Energy may reach an organism through several feeding steps, but trace the pathway backwards: the original input to the biological system is light energy from the Sun.
Plants and food contain chemical energy, but they are not the principal original input. For the biological systems in this syllabus, answer the Sun or sunlight.
Trace energy from sunlight to the environment
Light energy from the Sun is absorbed by producers during photosynthesis and stored as chemical energy in organic molecules. Feeding transfers chemical energy from one organism to another.
Living organisms release energy during their life processes. Energy is eventually transferred to the environment as heat, including heat produced through respiration.
Follow the form as well as the direction: Sun — light energy → producer — chemical energy in food → consumer — chemical energy → environment — heat energy.
Energy flows through a biological system and eventually leaves as heat; it is not recycled. Light is the input, chemical energy is transferred between organisms, and heat is the eventual transfer to the environment.