Energy Flow in Ecosystems and Ecological Efficiency

Sunlight – the primary energy source for ecosystems

• Altitude and light intensity: The higher the altitude, the thinner the layer of air, resulting in stronger sunlight.

• Distance from the equator and light intensity: The further away from the equator, the weaker the sunlight, and the longer the daylight hours.

• Seasonal variation: Sunlight changes with the time of year. In summer, light is strong and days are longer, while in winter the opposite is true.

Energy flow through trophic levels

• Nutrient cycle: Energy is passed from lower trophic levels to higher trophic levels.

• Energy loss: As you go up the trophic levels, energy decreases due to energy loss through respiration, excretion, movement, etc.

Ecological efficiency

• Definition: Ecological efficiency is the percentage of energy transferred between trophic levels in an ecosystem. In other words, it reflects the efficiency of converting energy from one trophic level to another.

Note: Ecological efficiency is usually very low, typically only around 10% of energy is transferred from a lower trophic level to a higher one. This explains why food chains usually only have 4-5 trophic levels.