【正文】
ated over and over again, gradually involving all the islands in the chain.The species on the Galapagos Islands today, most of which occur nowhere else, descended from organisms that floated, flew, or were blown over the sea from the South American mainland For instance, the Galapagos island chain has a total of thirteen species of closely related birds called Galapagos finches These birds have many similarities but differ in their feeding habits and their beak type, which is correlated with what they eat Accumulated evidence indicates that all thirteen finch species evolved from a single small population of ancestral birds that colonized one of the isolated on the island after migrating from the mainland, the founder population may have undergone significant changes in its gene pool and bee a new species. [■] Later, a few individuals of this new species may have been blown by storms to a neighboring island. [■]Isolated on this second island, the second founder population could have evolved into a second new species, which could later recolonize the island from which its founding population emigrated.[■]Today each Galapagos island has multiple species of finches, with as many as ten on some islands.[■]:An introductory sentence for a brief summary of the passage is provided the summary by selecting the THREE answer choices that express the most important ideas in the passage. Some sentences do not belong in the summary because they express ideas that are not presented in the passage or are minor ideas in the passage.The geographic isolation of a population can result in the rise of a new species.Answer Choices can result when a geographic barrier forms and splits a population or when a few organisms somehow get carried across an existing geographic barrier and form a new population is more likely when an isolated population is small because significant genetic changes are more likely to occur in a small population than in a large one of the geographic isolation of the Galapagos Islands, the species that now inhabit them have gene pools that have not changed very much since the islands were first populated. populations are more easily isolated by geographic barriers than are populations of most other organisms because fish cannot move across areas where there is no water. Galapagos Islands are well situated for speciation because they provide opportunities for population isolation while also making occasional dispersions between islands possible. indicates that the first organisms to reach the Galapagos Islands were probably a small population of finches that,in less than two million years of isolation,evolved into thirteen species. focus on dinosaur extinction?A. Dinosaurs became extinct so long ago that no theory about their disappearance can be proven scientifically.B. Dinosaurs were not the only organisms that went extinct at the end of the Cretaceous period.C. More marine organisms went extinct during the Cretaceous than did dinosaur species.D. It is more important to understand how plankton and other marine organisms came to thrive during the Cretaceous period.5. According to paragraph 2, each of the following became extinct during the KT event EXCEPTA. early species of whalesB. marine reptilesC. various species of clamsD. many species of land plants6. What makes the extinction of “the ammonites” especially significant?A. They were among the largest creatures that ever lived.B. They existed at the lowest level of the food chain.C. They had been able to survive in the Mesozoic seas.D. They had survived many previous mass extinctions.7. The word “halted” in the passage is closest in meaning toA. slowedB. stoppedC. contractedD. declined8. The word “strictly in the passage is closest in meaning toA. exclusivelyB. mainlyC. initiallyD. Wrongly9. The word “crisis” in the passage is closest in meaning toA. collapseB. disturbanceC. critical situationD. loss10. How does paragraph 3 relate to paragraph 2?A. Paragraph 3 provides an alternative explanation to the one provided in paragraph 2.B. Paragraph 3 provides an explanation that satisfies the conditions set forth in paragraph 2.C. Paragraph 3 provides the facts to support the theory presented in paragraph 2.D. Paragraph 3 presents a theory that calls into question the position described in paragraph 2.paragraph 3According to one theory, the Age of Dinosaurs ended suddenly 65 million years ago when a giant rock from space plummeted to Earth. Estimated to be ten to fifteen kilometers in diameter, this bolide (either a et or an asteroid) was traveling at cosmic speeds of 2070 kilometers per second, or 45,000156,000 miles per hour. Such a huge mass traveling at such tremendous speeds carries an enormous amount of energy. When the bolide struck this energy was released and generated a huge shock wave that leveled everything for thousands of kilometers around the impact and caused most of the landscape to burst into flames. The bolide struck an area of the Yucatan Peninsula of Mexico known as Chicxulub, excavating a crater 1520 kilometers deep and at least 170 kilometers in diameter. The impact displaced huge volumes of seawater, causing much flood damage in the Caribbean. Meanwhile, the bolide itself excavated 100 cubic kilometers of rock and debris from the site, which rose to an altitude of 100 kilometers. Most of it fell back immediately, but some of itremained as dust in the atmosphere for months. This material, along with the smoke from the fires, shrouded Earth, creating a form of nuclear winter. According to puterized climate models, global temperatures fell to near the freezing point, photosynthesis halted, and most plants on land and in the sea died. With the bottom of the food chain destroyed, dinosaurs could not survive.11. Paragraph 3 answers all of the following questions EXCEPT:A. Why did the bolide fall to Earth?B. How fast was