Parental Care by Frogs Only an estimated 10 percent of anuran (frog and toad) species provide any kind of parental care. But within this 10 percent there is very great diversity ...

Coal's Rise and Fall Changes in the use of coal over time are reflected in the environment. In the eighteenth century most peppered moths had black spots on white wings, but in th...

    题目： Transportation and Economic Change in the Nineteenth-Century       Between 1820 and 1860,the American economy entered a new stage of develop...

题目： Biological Rhythms     Biologists have identified many types of biological rhythms, including daily, monthly, and annual rhythms. Among many animals, physiologic...

  Part 1 READING PASSAGE 1 Read the text on the next page and answer Questions 1-13. Prison: The Solution or the Problem? In the Netherlands and parts of the USA such as Jo...

  Agricultural Practices of the Maya   题目：     The Maya civilization flourished for centuries on the Yucatan Peninsula and other areas of Mesoamerica, reac...

  题目： French Gothic Cathedrals Gothic-style cathedrals, known for their impressive height. pointed arches, and intricate line patterns, are among the most elaborate s...

题目： The Emergence of the State Before there was agriculture, people lived in small, loosely organized bands or tribes that hunted for and collected food in the wild. The emerg...

The Origin of Flight in Birds 题目： Debate over avian origins was stimulated in 1861 when the 150-million-year-old fossil of a bird-like creature was unearthed. Called Archaeopt...

  Archaeoptertx and Flight 题目： It is not known whether Archaeopteryx, the earliest birdlike creature for which fossils have been found, could fly-but it probably did, at ...