SAT OG 2016 Reading - Test 3 reading 3

Questions 21-30 are based on the following
passage.


This passage is adapted from Thor Hanson, Feathers. ©2011 by Thor Hanson. Scientists have long debated how the ancestors of birds evolved the ability to fly. The ground-up theory assumes they were fleet-footed ground dwellers that captured prey by leaping and flapping their upper limbs. The tree-down theory assumes they were tree climbers that leapt and glided among branches.




At field sites around the world, Ken Dial saw a

pattern in how young pheasants, quail, tinamous,

and other ground birds ran a long behind their
parents.“ They jumped up like popcorn,” he said,
5 describing how they would flap their half-formed

wings and take short hops into the air. So when a

group of graduate students challenged him

to come up with new data on the age-old

ground-up-tree-down debate, he designed a project
10 to see what clues might lie in how baby game birds

learned to fly.
Ken settled on the Chukar Partridge as a

model species, but he might not have made his

discovery without a key piece of advice from the local
15 rancher in Montana who was supplying him with

birds. When the cowboy stopped by to see how

things were going, Ken showed him his nice, tidy

laboratory setup and explained how the birds’ first

hops and flights would be measured. The rancher
20 was incredulous. “He took one look and said, in

pretty colorful language, ‘What are those birds doing

on the ground? They hate to be on the ground! Give

them something to climb on!’”At first it seemed

unnatural—ground birds don’t like the ground? But
25 as he thought about it Ken realized that all the

species he’d watched in the wild preferred to rest on

ledges, low branches, or other elevated perches where

they were safe from predators. They really only used

the ground for feeding and traveling. So he brought
30 in some hay bales for the Chukars to perch on and

then left his son in charge of feeding and data

collection while he went away on a short work trip.
Barely a teenager at the time, young Terry Dial

was visibly upset when his father got back. “I asked
35 him how it went, ”Ken recalled, “and he said,

‘Terrible! The birds are cheating!’” Instead of flying

up to their perches , the baby Chukars were using

their legs. Time and again Terry had watched them

run right up the side of a hay bale, flapping all the
40 while. Ken dashed out to see for himself, and that

was the “aha” moment. “The birds were using their

wings and legs cooperatively, ”he told me, and that

single observation opened up a world of possibilities.
Working together with Terry ( who has since gone
45 on to study animal locomotion ), Ken came up with a

series of ingenious experiments, filming the birds as

they raced up textured ramps tilted at increasing

angles. As the incline increased, the partridges began

to flap, but they angled their wings differently from
50 birds in flight. They aimed their flapping down and

backward, using the force not for lift but to keep

their feet firmly pressed against the ramp.“ It’s like

the spoiler on the back of a race car ,”he explained,

which is a very apt analogy. In Formula One racing,
55 spoilers are the big aerodynamic fins that push the

cars downward as they speed along, increasing

traction and handling. The birds were doing the very

same thing with their wings to help them scramble

up other wise impossible slopes.
60 Ken called the technique WAIR, for wing-assisted

incline running, and went onto document it in a

wide range of species. It not only allowed young

birds to climb vertical surfaces within the first few

weeks of life but also gave adults an energy-efficient
65 alternative to flying. In the Chukar experiments,

adults regularly used WAIR to ascend ramps steeper

than 90 degrees, essentially running up the wall and

onto the ceiling.
In an evolutionary context, WAIR takes on
70 surprising explanatory powers. With one fell swoop

the Dials came up with a viable origin for the

flapping flight stroke of birds (something gliding

animals don’t do and thus a shortcoming of the

tree-down theory ) and an aerodynamic function for
75 half-formed wings ( one of the main drawbacks to the

ground-up hypothesis ).

Question 21 Which choice best reflects the overall sequence of events in the passage?