Energy Transfer in Ecosystems

Energy Transfer in Ecosystems

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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

Trophic levels define nutritional roles in an ecosystem.

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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.

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Examples: wolves, wildcats, eagles, sharks, and toothed whales.

Video Segments

During this lesson you will watch 5 short video segments. to watch each segment, click on the video preview image.

Multiple Choice

Which of these is not a heterotroph?

• producer

• primary consumer

• secondary consumer

• tertiary consumer

Multiple Choice

Which organisms would be found at trophic level 1 (first trophic level)?

• grasses

• mice

• hawks

• grasshoppers

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: Decomposer

Decomposers are organisms that break down dead material and waste (feces, dung). Decomposers include:

- Fungi

- Bacteria

- Worms

- Insects, including fly larvae (maggots) and many beetles

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 3 factors are most likely to affect biodiversity in an area?

• 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

Decomposers are

• Producers

• Autotrophs

• Heterotrophs

Multiple Select

Which organisms are considered decomposers? (Choose 3.)

• bacteria

• fungi

• bears

• trees

• dung beetles

Multiple Choice

A bird that eats both insects and seeds is a(n)

• herbivore

• omnivore

• carnivore

• producer

Multiple Select

Which of these organisms are producers? (Choose 3.)

• fungi

• wildflowers

• bacteria

• grasses

• trees

Multiple Choice

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

• heat, only

• heat and waste

• 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.

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Notice that in this energy pyramid there are many plants shown at the producer level, 4 rabbits, 2 snakes, and 1 eagle. 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.

Biomass Pyramids

Some biomass and energy pyramids have an alternate appearance that looks more like stacked blocks...but we still consider it a biomass pyramid. This diagram uses a large green box to show that a very large amount of plants is needed to support each hawk.

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