We sometimes show the amount of energy and matter in an ecosystem by level, with producers on the bottom and top consumers at the top. Why do these figures have a pyramid shape, with the smallest amount of energy and matter (biomass) in the portion representing the top predators?

Figures have a pyramid shape because there is no other shape which describes the amount or number of populations of living organisms in the ecosystem. The organisms which are maximum number of population i. e. Plants are placed at the bottom of the pyramid while the organisms which are less in number are placed at the top of the pyramid i. e. predators or tertiary consumers.