A species can occupy different trophic levels, depending on what it is eating; for example, an omnivore is a primary consumer when it eats plant leaves, but could be a secondary or tertiary consumer when it eats other animal species.

Food chains almost never have more than four or five trophic levels

Fluctuating population sizes at different trophic levels cause longer food chains to be less stable than shorter food chains

Producers always have the greatest biomass of any trophic level

All of these

Variety of organisms in an ecosystem

Genetic variation across the planet

Ecosystem variation

Herbivores eat plant material and are primary consumers

Herbivores eat plant material and are secondary consumers

Herbivores are secondary consumers

Herbivores are primary consumers

Saprotroph

Producer

Carnivore

Herbivore

Omnivore

Antelope

Flowering plant

Cacti

Kelp

The biomass at higher trophic levels needs a larger amount of biomass at lower levels to support it

The biomass at higher trophic levels needs a smaller amount of biomass at lower levels to support it

Decomposers consume at every trophic level

Plants cannot absorb toxins from the environment

The biomass at higher trophic levels needs to be equal to the amount of biomass at lower levels to support it

Photosynthesis

Carnivorous consumption

Decomposition

All of these

Heterotrophs

Autotrophs

Photoautotrophs

Biosphere producers

There is a unidirectional influence from higher to lower trophic levels

There is a unidirectional influence from lower to higher trophic levels

Lower trophic levels affect higher trophic levels unpredictably

Higher trophic levels affect higher trophic levels unpredictably

Trophic relationships are unpredictable and are dependent on environmental factors

The length of a food chain is limited by insufficient energy transfer through the food chain

The lower trophic levels provide sufficient energy for higher trophic levels

The abundance of organisms at higher trophic levels are supported by lower trophic energy

Several food chains linked together create food webs

Biomass increases with energy and trophic level