Final answer:
Organisms always found at the bottom of the energy pyramid are producers, like plants and phytoplankton, which produce their own food through photosynthesis and support the rest of the ecosystem.
Step-by-step explanation:
The type of organism always found at the bottom of the energy pyramid is a) Producers. These organisms, such as plants and phytoplankton, are called primary producers and are essential for bringing energy into the ecosystem through processes like photosynthesis.
They create not only their own food but also the food for other organisms in the ecosystem, making them the base of the energy pyramid. Energy then flows from the producers to various levels of consumers such as herbivores, carnivores, and omnivores. Decomposers break down dead organic matter, but they are generally not represented at the base of the energy pyramid, which focuses on the flow of energy through living organisms.