Which statement best exemplifies an edge effect?

Which statement best exemplifies an edge effect?

• A. Edge effects are typically negligible.
• B. Increased light at the boundary alters species composition at the edge.
• C. Edge effects occur only in aquatic habitats.
• D. Edge effects increase interior habitat area.

Answer: (B)

Edge effects arise when the boundary between two habitats creates a different set of conditions—like light, temperature, and moisture—that differs from the interior. Those altered conditions at the edge can favor different species than those found in the interior, changing the edge’s species composition. The statement about increased light at the boundary changing which species can live there directly captures this idea: the extra light modifies the microhabitat at the edge, leading to a different mix of plants and animals than in the surrounding areas. That is a classic example of how boundaries influence community structure. The other ideas don’t fit as well. Edge effects are not typically negligible; they occur in many habitats, not just aquatic ones; and they don’t usually increase interior habitat area—in fact, edges can expose more boundary area and sometimes reduce interior habitat through fragmentation.

Edge effects arise when the boundary between two habitats creates a different set of conditions—like light, temperature, and moisture—that differs from the interior. Those altered conditions at the edge can favor different species than those found in the interior, changing the edge’s species composition.

The statement about increased light at the boundary changing which species can live there directly captures this idea: the extra light modifies the microhabitat at the edge, leading to a different mix of plants and animals than in the surrounding areas. That is a classic example of how boundaries influence community structure.

The other ideas don’t fit as well. Edge effects are not typically negligible; they occur in many habitats, not just aquatic ones; and they don’t usually increase interior habitat area—in fact, edges can expose more boundary area and sometimes reduce interior habitat through fragmentation.