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Do more species develop in warm, tropical climates or cooler, temperate areas? It turns out the longtime answer—the tropics – may be wrong.
True, more different types of animals exist there than in places farther from the equator.
New research suggests that is because tropical species do not die out as readily. Cooler regions have a higher turnover rate, with more species developing but also more becoming extinct.
By analyzing the DNA of 618 mammal and bird species that lived in the past several million years, they were able to determine that new species develop more readily farther away from the tropics.
“It would take one species in the tropics 3 to 4 million years to evolve into two distinct species, whereas at 60 degrees latitude, it could take as little as 1 million years,” weir said.
“In other words, there’s a higher turnover of species in places like Canada, making it a hotbed of speciation, not the amazon,” said Schluter.
That, however, is balanced by a higher extinction rate in colder climates, so the tropics still have more diversity.
It also raises the question of whether a more variable climate causes more rapid evolution.
The next step is to look at changes in behavior and body form, comparing tropical and temperate areas.
Kenneth E. Filchak said, “scientists and naturalists have been wondering about patterns of diversity for well over a century. But these questions still hold a central place in science.”
He said the new report was “interesting and significant”, for its look at the process of evolution and patterns of diversity. One is left with the question of why.
Weir said the got interested in the topic while studying the effects of ice sheets on evolution. They found that new species developed more rapidly in areas that had been covered with ice sheets than in regions that did not have ice cover. That caused them to widen the research to cover a larger area. 【原创】
( ) 56. What did the subject discuss in the text?
Species evaluate quickly in a variable climate.
Species develop more in tropics than in temperate area.
Species develop more quickly in cooler areas.
Species have become extinct in cold climate.
(出题意图：本题侧重考察学生对文章主旨的正确把握。)
( ) 57. Why do species develop slowly in tropics? 【原创】
Because tropical species need more time to become different species.
Because tropical species have a long life.
Because tropical species in pattern of diversity are different.
Because tropical provide warm climate for species.
(出题意图：本题侧重考察学生对文章各类具体信息的理解)
( ) 58. The researchers still need to study ______.
how different climates affect species growth
what kind of climate makes species develop quickly
what are the effects of ice sheets on ecosystem
if species in tropics and cooler areas change in behavior and body form
( ) 59. What makes less diversity in colder climates? 【原创】
The process of evolution.
The ice sheets.
A higher extinction rate.
The cold climate.
(出题意图：本题侧重考察学生对文章各类具体信息的理解)
( ) 60. This text is most probably taken from a ______.【原创】
research paper
newspaper report
class presentation
geography textbook
(出题意图：本题侧重考察学生对文章体裁和观察细节的能力)
