Warblers A and B each catch ten insects. A takes eight from upper branches and two from lower branches. B takes three upper and seven lower. What resource is partitioned?

• Insect food divided by feeding height within the tree
• Insect food divided by feeding time within the tree
• Branch space divided by nesting height within the tree

In the standard two-species Lotka-Volterra competition model, which condition supports stable coexistence?

• One species grows from rarity against an established rival
• Both species grow from rarity against an established rival
• Both species decline from rarity against an established rival

Both species persist alone in a constant, well-mixed single-nutrient system with no other limits, enemies or immigration. A has R* = 3 mg/L; B has R* = 6 mg/L. What equilibrium outcome is predicted?

• B excludes A by lowering the nutrient to its own R* of 6 mg/L
• A excludes B by lowering the nutrient to its own R* of 3 mg/L
• Both persist with the nutrient halfway between their two R* values

Matched plots are randomly assigned to competitor removal or sham handling. Habitat stays alike. The remaining species expands its diet only after removal. What does this support?

• The species avoided those foods because of its inherited feeding preference
• The competitor's presence had restricted the species' use of those foods
• Handling disturbed the plots and changed the species' use of those foods

Two rodent species prefer different seed sizes. No data on seed scarcity or population trends are available. Which conclusion is supported?

• Diet differences suggest partitioning; competition and persistence remain untested
• Diet differences establish coexistence; seed limitation remains untested
• Diet differences establish competition; long-term persistence remains untested

A predator reduces a dominant competitor. The shared resource increases, and a weaker competitor then persists. Which indirect mechanism fits these observations?

• The predator provides food directly to the weaker species after each hunt
• The predator lowers the weaker species' demand for the shared resource
• Predation reduces resource use by the dominant rival, leaving food available

In the standard two-species competition model, each species declines when rare against its established rival. This proves the same species wins from every starting mixture.

A plant grows better in nitrogen-poor soil when associated with nitrogen-fixing microbes. Which mechanism can explain the advantage?

• Microbes convert nitrogen from the plant into gas that escapes to the atmosphere
• Microbes convert carbon from their plant partner into nitrogen that the plant can use
• Microbes convert atmospheric nitrogen into forms that their plant partner can use