A grassland's producers fix 10,000 energy units. Using the 10% rule, about how many units are available to secondary consumers?

Use the energy pyramid. About how much energy reaches the primary consumers?

Algae contain 100,000 kJ, zooplankton eat algae, minnows eat zooplankton, and herons eat minnows. About how much energy is available to minnows?

Why is much of the energy eaten by an herbivore unavailable to the next trophic level?

A field produces 5,000 kg of plant biomass. If herbivores convert about 10% into biomass, what biomass could support the next trophic level?

A primary consumer obtains 2,000 kJ from plants. Roughly how much energy is available to a secondary consumer that eats it?

Use the energy pyramid. Which trophic level has about 80 energy units available?

A student says energy lost between trophic levels has vanished. What is the best correction?

A community feeds people beans directly rather than feeding beans to cattle first. Compared with eating beef, what does this change do to producer energy needed per food energy delivered?

A food chain is corn → caterpillar → songbird → hawk. If corn captures 1,000,000 J, about how much is available to the hawk?

In a lake food web, zooplankton receive 600 kJ from algae. About how much energy can small fish receive from zooplankton?

Dead leaves enter a forest detrital food web. What happens to the chemical energy in those leaves when decomposers use it?

Which process returns nitrogen from soil compounds to the atmosphere as nitrogen gas?

Fertilizer runoff reaches a lake, algae bloom, and decomposers later use oxygen while breaking down dead algae. What condition is most likely to follow?

Legumes with root-nodule bacteria gain usable nitrogen from atmospheric N₂. What transformation do the bacteria perform?

Wastewater releases ammonium into a stream, and bacteria oxidize it to nitrate. What nitrogen-cycle process occurred?

Microbes break down organic nitrogen in livestock manure and produce ammonium. What process is this?

A reforestation project increases the mass of living trees. Which carbon-cycle process removes CO₂ from the atmosphere into that biomass?

A power plant burns coal that formed from ancient biomass. What is the immediate carbon-cycle effect?

A forest is cleared and its wood is burned for development. Which change most directly increases atmospheric CO₂ over the short term?

A city replaces a permeable field with parking lots. During a later dry spell, what change is most likely in a nearby stream that is fed by groundwater?

After heavy irrigation, nitrate fertilizer moves downward through soil into a shallow well. What transport process moved the nitrate?

Phosphate fertilizer erodes from a farm into a reservoir. Where is phosphorus most commonly stored long term in its cycle?

A dam creates a broad reservoir in a hot, dry region. Which water-cycle flux may increase from the enlarged exposed surface?

Two squirrel species feed on the same limited nuts, and both have lower survival where their ranges overlap. What interaction is occurring?

Ticks gain blood meals from deer, while heavily infested deer lose blood and may transmit disease. What interaction is this?

A bee obtains nectar from a flowering crop and transfers pollen that helps the plant reproduce. What interaction is shown?

Cattle egrets eat insects flushed by grazing cattle, while the cattle are not significantly helped or harmed. What interaction is this?

Wolves capture and consume elk in a protected landscape. What species interaction directly occurs?

A nonnative grass and a native grass occupy the same restored prairie plots, and each produces fewer seeds when the other is present. What interaction limits both populations?

After sea otters are removed, sea urchins increase and kelp forests decline. Which lost interaction most directly allowed the urchin increase?

A pesticide reduces native bee populations, and a nearby orchard produces less fruit. Which interaction was disrupted?

An introduced insect consumes the leaves of a native shrub, reducing the shrub's growth and seed production. What interaction describes the insect's effect?

An introduced predatory fish eats juvenile native fish in a lake, and the native fish population declines. What interaction is directly responsible?

Engineers raise a pipeline on supports across land with permanently frozen subsoil. Which biome creates this concern?

Use the climatograph for Station B. Which biome does this climate best match?

A site receives about 20 cm of rain annually, has sparse shrubs, and is irrigated for crops. Which biome is it, and what soil problem can irrigation promote?

A farmer converts native temperate grassland to annual row crops. Which ecological function is most reduced when deep perennial roots are removed?

Irrigation water evaporates from a field faster than salts are flushed downward. What soil change is most likely?

After a watershed is heavily paved, a storm produces a higher and faster stream peak. What landscape change most directly caused that pattern?

A highway splits a forest into isolated patches. Why can a wildlife corridor help conserve populations in the patches?

After rain, a stream beside a cleared bank has higher turbidity than a stream with a forested riparian buffer. What service did the buffer provide?

A farm field is abandoned, but its soil, roots, and seed bank remain. Which process is most likely to begin?

A retreating glacier exposes bare rock with no soil. Which type of succession begins as lichens and other pioneer species colonize it?

A lava flow cools into bare rock with no soil or surviving organisms. Which organisms are most likely to colonize the rock first?

A wildfire kills trees but leaves soil, buried seeds, and some roots intact. What recovery pattern is expected?

A mine removes all topsoil and exposes bedrock. Before shrubs can establish, what must pioneer organisms help create?

A reclaimed strip mine receives replaced topsoil and native seeds. Which factor most directly makes recovery faster than on exposed bedrock?

A hurricane uproots many trees but leaves the forest soil in place. Which plants are most likely to grow first in the sunny openings?

Wind exposes a newly formed sand dune with little organic matter, and pioneer grasses begin trapping sediment. What is their role in succession?