Energy and 10% Rule

What are the three main groups of primary producers?

Plants, algae, and bacteria.

What is an autotroph?

An organism that uses energy from sunlight to make complex organic compounds from simple inorganic molecules.

What is photosynthesis?

The process of using sunlight to produce sugars from carbon dioxide and water.

What does photosynthesis require?

Sunlight.

What is cellular respiration?

The process of breaking down sugars to release energy for growth, reproduction, and other life processes.

What are the products of respiration shown in the lecture?

Carbon dioxide, water, waste, and heat; energy is used to build structures and maintain support systems.

What is gross primary productivity (GPP)?

The amount of energy created by autotrophs before subtracting energy lost through respiration.

What is net primary productivity (NPP)?

The chemical energy produced by autotrophs that remains after the costs of respiration.

What is the formula for NPP?

NPP = GPP − respiration.

How can GPP, respiration, and NPP be compared to finances?

GPP is income, respiration is operating costs, and NPP is profit.

What is biomass?

The mass of living biological organisms in a given area or ecosystem at a given time.

How does the lecture say we measure NPP in ecological systems?

By tracking biomass.

What two climate variables are associated with NPP in the lecture's graphs?

Precipitation and temperature.

What general relationship does the lecture show between precipitation and NPP?

NPP generally increases as precipitation increases, then the increase levels off.

What general relationship does the lecture show between temperature and NPP?

NPP generally increases as temperature rises, then levels off at higher temperatures.

What is a trophic level?

The position an organism occupies in a food chain.

What is a producer's role in a food chain?

It forms the base by producing organic matter using an energy source such as sunlight.

What is a primary consumer?

An organism that feeds on producers.

What is a secondary consumer?

An organism that feeds on primary consumers or other consumers at a lower trophic level.

What is an apex predator?

A predator at the top of a food chain, with no higher predator shown in that chain.

What is ecological efficiency?

The rate at which energy or biomass is transferred from one trophic level to the next.

What does the 10% rule describe?

Roughly 10% of energy or biomass is transferred to the next trophic level; about 90% is lost at each transfer.

If producers contain 1,000 g/m² of biomass, about how much reaches the next level under the 10% rule?

About 100 g/m².

If a trophic level contains 100 g/m², about how much reaches the next level under the 10% rule?

About 10 g/m².

If producers contain 1,000 g/m², about how much reaches a level two transfers above them?

About 10 g/m².

Why is less biomass available at higher trophic levels?

Only a small fraction—about 10%—is transferred to the next level at each step.

What organisms are used as an example of producers in the temperate woodland slides?

Plants.

What role do termites play in the temperate woodland example?

They are first-order grazers (primary consumers).

What role do songbirds such as the indigo bunting play in the temperate woodland example?

They are first-order predators.

According to the lecture, how do songbirds compare with insects in temperate woodlands?

Songbirds are about ten times larger but about one tenth as abundant.

What role do red foxes play in the temperate woodland example?

They are second-order predators.

According to the lecture, how do foxes compare with songbirds?

Foxes are about ten times larger but about one tenth as abundant.

What role do mountain lions play in the temperate woodland example?

They are apex predators.

How does the lecture describe mountain lions compared with foxes?

Mountain lions are much larger but much less abundant.

Which tree species is used in the Minnesota 10% rule example?

Bur oak (Quercus macrocarpa).

How long can a bur oak live, according to the lecture?

Nearly 500 years.

What do the words Quercus and macrocarpa mean in the bur oak's scientific name?

Quercus means “oak,” and macrocarpa means “large fruit.”

What is a muskrat?

A medium-sized rodent found in wetlands and native to North America.

What does the lecture say golden eagles mainly prey upon in North America?

Rabbits and ground squirrels.

What is a biomass pyramid?

A diagram showing the amount of biomass at different trophic levels, typically decreasing toward the top.

What biomass values are shown in the lecture's biomass pyramid?

1,000 g/m² at the producer level, 100 g/m² at the next level, and 10 g/m² at the highest level shown.

What is the main implication of the 10% rule for large predators?

Much less energy and biomass is available at higher trophic levels, helping explain why large predators are less abundant.

What does the 'leaky pipes' analogy suggest about ecosystems?

Energy transfer through ecosystems is inefficient; some energy is lost rather than passed along.

Why can't all energy captured by plants be passed to consumers?

Plants use some of the captured energy for respiration and their own life processes, and energy is lost as heat and waste along transfers.

What is the difference between GPP and NPP?

GPP is total energy created by autotrophs before respiration costs; NPP is what remains after respiration.