When considering an energy pyramid, it's important to remember that energy is lost as it moves through each trophic level. This loss of energy occurs mainly through metabolic processes like respiration and heat production.
Here's why there are typically fewer organisms at the top of an energy pyramid:
1. **Energy Loss:** At each trophic level, energy is lost, usually around 90% due to metabolic processes. This means that only about 10% of the energy from one trophic level is passed on to the next.
2. **Calculation Example:** Let's say a plant absorbs 1000 units of energy from the sun. The primary consumer (herbivore) that eats the plant will only receive around 100 units of energy (10% of 1000). If a secondary consumer (carnivore) eats the primary consumer, it will only receive about 10 units of energy (10% of 100).
3. **Accumulation of Energy Loss:** As we move up the energy pyramid, the energy available decreases significantly. This means that fewer organisms can be supported as we reach the top due to the cumulative effects of energy loss at each level.
4. **Example Calculation:** Following the example above, by the time we reach the top predator (tertiary consumer), they would receive only about 1 unit of energy. This limited energy availability at the top level of the pyramid results in fewer organisms being able to be sustained.
In summary, the decrease in available energy due to energy loss at each trophic level results in a pyramid-shaped distribution of organisms, with fewer individuals at the top due to the limited energy resources available to support them.
