Amphibian orientation: an unexpected observation     

Twitty V  Grant D  Anderson O 《Science (New York, N.Y.)》1967,155(3760):352-353

The study of homing movements of displaced newts (Taricha rivularis) revealed unexpected features of the migratory behavior of amphibians. Newts leaving the breeding stream in the spring move not directly uphill but at an angle carrying them upstream. When they emerge after summer estivation this tendency is not evident in captures made during the autumn and winter. During the latter period, however, newly metamorphosed frogs (Rana boylii) show the same pronounced upstream migration that characterizes T. rivularis in the spring.  相似文献   

Hybridization of bird species     

Grant PR  Grant BR 《Science (New York, N.Y.)》1992,256(5054):193-197

Hybridization, the interbreeding of species, provides favorable conditions for major and rapid evolution to occur. In birds it is widespread. Approximately one in ten species is known to hybridize, and the true global incidence is likely to be much higher. A longitudinal study of Darwin's finch populations on a Galápagos island shows that hybrids exhibit higher fitness than the parental species over several years. Hybrids may be at an occasional disadvantage for ecological rather than genetic reasons in this climatically fluctuating environment. Hybridization presents challenges to the reconstruction of phylogenies, formulation of biological species concepts and definitions, and the practice of biological conservation.  相似文献   

Grand banks and j-anomaly ridge: a geological comparison     

Gradstein FM  Grant AC  Jansa LF 《Science (New York, N.Y.)》1977,197(4308):1074-1076

Geological and geophysical evidence supports the hypothesis that the J-anomaly ridge was a part of the Grand Banks in (late) Early Cretaceous time.  相似文献   

Avian strategies     

Grant PR 《Science (New York, N.Y.)》1980,209(4457):682-683

  相似文献   

Acid precipitation in the Western United States     

Lewis WM  Grant MC 《Science (New York, N.Y.)》1980,207(4427):176-177

Precipitation chemistry data from a rural area at an elevation of 2900 meters near the Continental Divide in Colorado show unexpectedly low pH values for bulk precipitation. A significant downward trend in pH over the last 3 years is associated with increasing amounts of nitric acid in precipitation.  相似文献   

SIR ISAAC NEWTON AND THE SENSITIVE RADIOMETER     

Grant K 《Science (New York, N.Y.)》1945,102(2647):311-312

  相似文献   

LUNAR RINGS     

Hanna GD  Grant WM 《Science (New York, N.Y.)》1935,81(2088):18-19

  相似文献   

Ecological speciation in South Atlantic island finches     

Ryan PG  Bloomer P  Moloney CL  Grant TJ  Delport W 《Science (New York, N.Y.)》2007,315(5817):1420-1423

Examples of sympatric speciation in nature are rare and hotly debated. We describe the parallel speciation of finches on two small islands in the Tristan da Cunha archipelago in the South Atlantic Ocean. Nesospiza buntings are a classic example of a simple adaptive radiation, with two species on each island: an abundant small-billed dietary generalist and a scarce large-billed specialist. Their morphological diversity closely matches the available spectrum of seed sizes, and genetic evidence suggests that they evolved independently on each island. Speciation is complete on the smaller island, where there is a single habitat with strongly bimodal seed size abundance, but is incomplete on the larger island, where a greater diversity of habitats has resulted in three lineages. Our study suggests that the buntings have undergone parallel ecological speciation.  相似文献   

A closer look at water-related geologic activity on Mars     

McEwen AS  Hansen CJ  Delamere WA  Eliason EM  Herkenhoff KE  Keszthelyi L  Gulick VC  Kirk RL  Mellon MT  Grant JA  Thomas N  Weitz CM  Squyres SW  Bridges NT  Murchie SL  Seelos F  Seelos K  Okubo CH  Milazzo MP  Tornabene LL  Jaeger WL  Byrne S  Russell PS  Griffes JL  Martínez-Alonso S  Davatzes A  Chuang FC  Thomson BJ  Fishbaugh KE  Dundas CM  Kolb KJ  Banks ME  Wray JJ 《Science (New York, N.Y.)》2007,317(5845):1706-1709

Water has supposedly marked the surface of Mars and produced characteristic landforms. To understand the history of water on Mars, we take a close look at key locations with the High-Resolution Imaging Science Experiment on board the Mars Reconnaissance Orbiter, reaching fine spatial scales of 25 to 32 centimeters per pixel. Boulders ranging up to approximately 2 meters in diameter are ubiquitous in the middle to high latitudes, which include deposits previously interpreted as finegrained ocean sediments or dusty snow. Bright gully deposits identify six locations with very recent activity, but these lie on steep (20 degrees to 35 degrees) slopes where dry mass wasting could occur. Thus, we cannot confirm the reality of ancient oceans or water in active gullies but do see evidence of fluvial modification of geologically recent mid-latitude gullies and equatorial impact craters.  相似文献   

Territorialism in Two Species of Salamanders     

Grant WC 《Science (New York, N.Y.)》1955,121(3135):137-138

  相似文献