Final answer:
Energy flows through an ecosystem via a chain of energy transfers from producers to consumers, known as food chains and webs. Energy efficiency decreases with each transfer up trophic levels due to loss of energy as heat. The sun is the main source of energy for most ecosystems.
Step-by-step explanation:
The energy flow between organisms in an ecosystem starts with the primary producers, which are mostly plants. These producers harness energy directly from the sun through photosynthesis and convert it into chemical energy in the form of glucose. This energy is then transferred to primary consumers or herbivores when they consume the plants. Following this, when these herbivores are consumed by secondary consumers or carnivores, the energy continues to flow through the ecosystem. This chain of energy transfer is structured into what ecologists term as food chains and food webs, showing the direct feeding relationships between organisms in an ecosystem.
Within these food chains and webs, energy efficiency decreases with ascending trophic levels. This is because energy is lost as heat when organisms use it to maintain their life processes and is not entirely passed on to the next level. These losses mean that the higher an organism is in the food chain, the less energy it gets from its food source. The concept of ecological pyramids visualizes this effectiveness and movement of energy across different trophic levels, which is crucial for understanding ecosystem structure and dynamics. Additionally, the majority of ecosystems depend on the sun as the ultimate source of energy, except for a few ecosystems based on chemosynthesis from inorganic chemicals.