Organisms that have this ability possess a specialized leading digit known as an alula. Animals that have (-5[1])lost this ability tend to have symmetrical remiges (“re-MEE-jez”). Echelon (10[1])formations (-5[1])are adopted by groups of organisms with this ability. Structures that confer this ability are categorized as (10[1])primary or secondary, and can include small serrations (10[1])to reduce noise. (10[1]-5[1])Tree-down (10[1])and ground-up (10[1]-5[1])are two theories for the evolution (10[3])of this ability, (10[7]-5[4])seen in the transition (10[1]-5[3])species (-5[1])Archaeopteryx (10[8]-5[4])(“arch-ee-op-te-rix”). Organisms (10[5]-5[1])with (10[1])this (10[2])ability have hollow bones. (10[9])For 10 points, (10[2])name this ability (10[3])to generate (10[1])lift (10[1])in the air possessed by animals like birds. (10[3])■END■ (10[8])