The evolution of Birds
The Origin of Birds
P1 Analysis of birds and of reptilian fossils indicate that birds belong to the group called therapods. Several species of dinosaurs closely related to birds had feathers with vanes, and a wider range of species had filamentous feathers. Such findings imply that feathers evolved long before powered flight. Among the possible functions of these early feathers were insulation, camouflage, and courtship display.
1. Which of the sentences below best expresses the information in the highlighted statement in the passage? The other choices change the meaning or leave out important information.
A. Results of investigations indicate that birds probably flew before they had feathers
B. Analysis suggests that birds did not fly immediately after they had developed feathers
C. The time frame for the evolution of feathers is not clear from the studies cited
D. According to researchers, birds developed feathers in order to achieve flight
Derived Characteristics of Birds
P2 Many of the characteristics of birds are adaptations that facilitate flight, including weight-saving modifications that make flying more efficient. For example, birds lack a urinary bladder and the females of most species have only one ovary. Living birds are also toothless, an adaptation that trims the weight of the head.
2. The word modifications in the passage is closest in meaning to
A. Made different
B. Made better
C. Made smaller
D. Made modern
3. According to paragraph 2, how did birds adapt to achieve efficient flight?
A. They developed new lighter organs
B. Their muscles became smaller over time
C. Most of their weight was distributed in their heads
D. Heavy teeth disappeared during evolution
P3 A bird’s most obvious adaptations for flight are its wings and feathers. Feathers are made of the protein B-keratin, which is also found in the scales of other reptiles. The shape and arrangement of the feathers form the wings into airfoils, and they illustrate some of the same principles of aerodynamics as the wings of an airplane. Power for flapping the wings comes from contractions of large pectoral (breast) muscles anchored to a keel on the sternum (breastbone). Some birds, such as eagles and hawks, have wings adapted for soaring on air currents and flap their wings only occasionally; other birds, including hummingbirds, must flap their wings continuously to stay aloft. Among the fastest birds are the appropriately named swifts, which can fly up to 170 km/hr.
4. In paragraph 3, how does the author explain the term “keratin”?
A. By identifying it in feathers and scales
B. By comparing it to airfoils
C. By providing a definition in the text
D. By describing the way that it looks
5. According to paragraph 3, which of the following is true about the wings of birds?
A. All birds flap their wings constantly by using breast muscles
B. Eagles and hawks have wings that propel them at 170 km/hr
C. The airfoils of birds function like the wings on airplanes
D. Wings are attached to airfoils in the birds skeletal structure
6. The word principles in the passage is closest in meaning to
A. Criticism
B. Examples
C. Topics
D. Rules
P4 A Flight provides numerous benefits. B It enhances hunting and scavenging; many birds consume flying insects, an abundant, highly nutritious food resource. C Flight also provides ready escape from earthbound predators and enables some birds to migrate great distances to exploit different food resources and seasonal breeding areas. D
12. Look at the four squares that show where the following sentence could be inserted in the passage.
Furthermore, migration allows birds to avoid climates that are too hot or too cold during certain seasons.
Where could the sentence best be added?
Click on a square to insert the sentence in the passage.
P5 Flying requires a great expenditure of energy from an active metabolism. Birds are endothermic; they use their own metabolic heat to maintain a high, constant body temperature. Feathers, and in some species layers of fat, provide insulation that enables birds to retain their body heat. The lungs have tiny tubes leading to and from elastic air sacs that improve airflow and oxygen uptake. This efficient respiratory system with a four-chambered heart keep tissues well supplied with oxygen and nutrients, supporting a high rate of metabolism.
9. According to the passage, how did therapods develop flight?
A. Engineers believe that they flapped their wings to gain lift
B. Scientists have proposed several different possibilities for flight
C. Paleontologists think that they glided down from high trees
D. Researchers confirm that flight began with running and jumping
P6
Flight also requires both acute vision and fine muscle control. Birds have excellent eyesight. The visual and motor areas of the brain are well developed, and the brain is proportionately larger than those of amphibians and nonbird reptiles. Birds generally display very complex behaviors, particularly during breeding season, when they engage in elaborate courtship rituals.
7. The word elaborate in the passage is opposite in meaning to
A. Simple
B. Quiet
C. Sad
D. short
11. All of the following are mentioned as adaptations to the bird’s anatomy to accommodate flight EXCEPT
A. The arrangement of feathers
B. A high metabolic rate
C. Very sharp eyes
D. Small legs and feet
P7 How did flight evolve in the therapods? In one scenario, feathers may have enabled the small, running dinosaurs chasing prey or escaping predators to gain extra lift as they jumped up into the air. Or, small dinosaurs could have gained traction as they ran up hills by flapping their feathered forelimbs- a behavior seen in birds today. In a third scenario, some dinosaurs could have climbed trees and glided, aided by feathers. Whether birds took to the air from the ground up or from the trees down, an essential question being studied by scientist ranging from paleontologists to engineers is how their efficient flight stroke evolved.
8. The word essential in the passage is closest in meaning to
A. Very clear
B. Very important
C. Very difficult
D. Very new
P8 By 150 million years ago, feathered therapods had evolved into birds. Archaeopteryx, which was discovered in a German limestone quarry in 1861, remains the earliest known bird. It had feathered wings but retained ancestral characteristics such as teeth, clawed digits in its wings, but a long tail. Archaeopteryx flew well at high speeds, but unlike a present-day bird, it could not take off from a standing position. Fossils of later birds from the Cretaceous show a gradual loss of certain ancestral dinosaur features, such as teeth and clawed forelimbs, as well as the acquisition of innovations found in extant birds, including a short tail covered by a fan of feathers.
Glossary
Cretaceous: a time period, 144 – 65 million years ago
10. According to paragraph 8, what can be inferred about Archaeopteryx?
A feathered fantail was prominent
Lift off was achieved by running or gliding
Teeth had been replaced by a beak
The habitat extended throughout Europe
13. Directions: An introduction for a short summary of the passage appears below. Complete the summary by selecting the THREE answer choices that mention the most important points in the passage. Some sentences do not belong in the summary because they express ideas that are not included in the passage or are minor points from the passage.
This question is worth 2 points.
Birds evolved 150 million years ago.
* *
A. Birds and reptiles are most probably related.
B. Feathers are among the most unusual evolutionary changes.
C. Many structural adaptations were required for birds to fly.
D. Therapods are relatively small, meat-eating dinosaurs.
E. There are a number of advantages for creatures that fly
F. Migration patterns are typical of many species of birds.
ANS:
1. B, 2. A 3. D 4. A
5. C 6. D 7. A 8. B
9. B 10. B 11. D 12. C 13. A,C,E
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