Organisms that have this ability possess a specialized leading digit known as an alula. Animals that have lost this ability tend to have symmetrical remiges (“re-MEE-jez”). Echelon formations (-5[1])are adopted by groups of organisms with this ability. Structures that confer this ability are categorized as primary or secondary, and can include small serrations to reduce noise. (10[1])Tree-down and ground-up are two theories for the evolution of this ability, (-5[1])seen in the transition species Archaeopteryx (10[1])(“arch-ee-op-te-rix”). Organisms (10[1])with this ability have hollow bones. (10[3])For 10 points, name this ability to generate (10[1])lift in the air possessed by animals like birds. (10[1])■END■