Trophic Levels and Energy Pyramids

Energy Pyramids and Biomass

​E.Q: How can an energy Pyramid be used to explain the relationship between amount of energy and population size?

In this lesson we will

• Review food chains and food webs

• Define biodiversity

• Explore energy transfer among trophic levels

• Define biomass

• Understand why pyramids are used to show both energy transfer and biomass

Vocabulary: Trophic Level

Recall that trophic levels are used to group organisms according to their nutritional role in an ecosystem.

For example, in Yellowstone National Park, willow trees, aspen trees, and berry bushes are producers. Elk, beavers, and bees are herbivores.

Vocabulary: Apex predator

An apex predator is a carnivore that is at the top of a food chain, for example, wolves, wildcats, eagles, sharks, and toothed whales.

Multiple Choice

How much of a plant's energy is transferred to the insects that eat it?

• 1%

• 10%

• 50%

• 100%

Multiple Choice

Which of these is an apex predator?

• elephant

• elk

• eagle

Multiple Choice

If an apex predator is removed from an ecosystem, which organisms are affected?

• the predator's prey, only

• primary and secondary consumers

• it is possible that all organisms in the ecosystem will be affected in some way

Vocabulary: Biodiversity

Biodiversity is the degree of variety of plant and animal life in an area. Deserts have low biodiversity due to the limited water supply. Rainforests have high biodiversity thanks to a moist environment.

Multiple Select

Which factors are most likely to affect biodiversity in an area? Choose all that apply.

• climate

• size of the area

• time of day

• human activity

Multiple Choice

Biodiversity in an ecosystem affects a species' ability to recover from a problem in the ecosystem.

• True

• False

Multiple Choice

The reason only 10% of energy is transferred up to the next trophic level is that 90% is lost as

• food

• heat

• nutrition

Multiple Choice

In healthy ecosystems

• there are many more producers than consumers

• thee are an equal number of producers and consumers

• consumers outnumber producers

Multiple Choice

In a healthy ecosystem, the organism with the smallest population would be

• plants

• grasshoppers

• eagles

• sparrows

Vocabulary: Biomass

Biomass is the mass of living organisms, in total, or at each level of the energy pyramid.

Notice that in this energy pyramid there are many plants shown at the producer level, 4 rabbits, 2 snakes, and 1 eagle. This illustrates that at as we go up the energy pyramid, fewer individuals, or total mass for a species, can be supported.

Biomass example

Elephants are herbivores. They eat only plants, placing them on the second trophic level in an ecosystem. Since each adult African bush elephant weighs about 13,000 pounds (huge biomass!), they require a large amount of plant life in a large area to sustain the species. When studying the amount of biomass an ecosystem can support, we must consider both the number of individuals and their size.

Multiple Choice

What will you always find at the first level (bottom) of an energy pyramid?

• plants

• animials

• decomposers

Multiple Choice

The top of a biomass pyramid is small because only a few apex predators can be supported in an ecosystem.

• True

• False

Multiple Choice

Based on the model, which consumers would receive the greatest amount of energy captured by the producers in their food chains? 

• Beluga Whale

• Polar Bear and Arctic Hare

• Ptarmigan and Arctic Bumble

• Lichens and Shrubs

Multiple Choice

In this energy pyramid, what is the proper name for ANY ORGANISM ABOVE THE PRODUCER LEVEL?

• decomposers

• consumers

• producers

• omnivores

Multiple Choice

In the energy pyramid here, which organisms have the most energy available?

• Producers

• Carnivores

• Herbivores

• Top Predator

Multiple Choice

In the energy pyramid here, how much of the energy in each level gets lost as heat or used by the organism for survival?

• 80%

• 90%

• 10%

• 20%

Multiple Choice

If these organisms were arranged in a food pyramid, which organism would have the least amount of total energy available?

• coyote

• insect

• lizard

• shrub

Multiple Choice

In the energy pyramid here, how much of the energy in the producers gets passed to the herbivores?

• 10%

• 20%

• 80%

• 90%

Multiple Choice

A food pyramid represent the relative amount of energy in trophic levels. Which of the following correctly shows a food pyramid?

• A

• B

• C

• D

Multiple Choice

The diagram represents a model of a food pyramid.  Which statement best describes what happens in this food pyramid?

• More organisms die at higher levels than at lower levels, resulting in less mass at higher levels.

• Energy is lost to the environment at each level, so less mass can be supported at each higher level.

• When organisms die at higher levels, their remains sink to lower levels, increasing the mass of lower levels.

• Organisms decay at each level, and thus less mass can be supported at higher levels

Multiple Choice

A pyramid shape is used to show the amount of available energy at each trophic level because... 

• energy decreases as you go up the food chain, just like the pyramid shape gets smaller as you go up. 

• energy increases up the food chain just like the pyramid shape gets smaller as you go up. 

• energy amounts are the same at each trophic level