Final answer:
In ecological pyramids, there is a general trend of decreasing number of individuals, total biomass, and increasing organism size with each ascending trophic level.
Step-by-step explanation:
Ecological pyramids visually represent the structure of ecosystems by showing the distribution of biomass, number of organisms, and energy across different trophic levels. Typically, these pyramids illustrate that as one moves from lower to higher trophic levels—from producers to primary consumers (herbivores), and then to secondary consumers (carnivores) and so on—there is often a decrease in the number of individuals, a decrease in the total biomass, and an increase in the size of the organisms.
For example, starting with producers, which have the largest biomass due to their high numbers, there is a large amount of energy available at this level. If producers in an ecological pyramid have 1,000,000 kilocalories of energy, then the primary consumers would have significantly less due to energy loss through metabolism and heat. The energy transfer efficiency from one trophic level to the next is typically around 10%, which means that primary consumers would have approximately 100,000 kilocalories of energy available from producers. As a direct result, there are fewer organisms as we move up the trophic levels since less energy means the environment can sustain smaller populations of larger organisms.
An inverted biomass pyramid occurs in ecosystems where producers, like phytoplankton, have a rapid turnover rate and are consumed quickly by the primary consumers, resulting in a lower biomass at any given moment. Despite this, they can reproduce quickly enough to support the ecosystem. An example of this is found in the English Channel where the biomass of the primary consumers (zooplankton) exceeds that of the phytoplankton. In contrast, energy pyramids are always upright because each trophic level loses energy, primarily due to metabolic processes.