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What is a pyramid of biomass?

A pyramid of biomass is a graphical representation of biomass present in each trophic level of an ecosystem at a given time.

In more detail, a pyramid of biomass illustrates the relative amount of living organic matter available at each trophic level in an ecosystem. Trophic levels refer to the different stages in a food chain, starting with producers at the bottom (like plants), followed by primary consumers (like herbivores), secondary consumers (like carnivores), and so on.

The pyramid shape is used because it typically represents the decrease in biomass from the bottom to the top. This means that there is usually more biomass at the lower levels (plants) and less at the higher levels (animals). This is because energy is lost at each trophic level due to factors such as respiration, excretion, and non-consumed parts.

However, it's important to note that not all pyramids of biomass are 'perfect' pyramids. In some aquatic ecosystems, for example, the pyramid can be inverted. This is because the producers (phytoplankton) have a smaller biomass than the primary consumers (zooplankton), but reproduce very quickly.

In your studies, you'll often use pyramids of biomass to understand the flow of energy through an ecosystem. They're a useful tool for visualising the general principle that energy decreases as you move up the food chain. This principle is known as the '10% rule', which states that, on average, only about 10% of the energy from one trophic level is transferred to the next.

Remember, a pyramid of biomass is a snapshot in time, as the biomass in an ecosystem can change over different seasons and for many other reasons. So, while it's a helpful model, it doesn't capture the full complexity of nature.

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