Onset of Spermatogenesis in Meishan and Large White Male Piglets     

MT Hochereau-de Reviers  C Perreau  V Rahal-Perola  D Royere 《Reproduction in domestic animals》1999,34(3-4):213-217

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Pleistocene extinction of genyornis newtoni: human impact on australian megafauna     

GH Miller  JW Magee  BJ Johnson  ML Fogel  NA Spooner  MT McCulloch  LK Ayliffe 《Science (New York, N.Y.)》1999,283(5399):205-208

More than 85 percent of Australian terrestrial genera with a body mass exceeding 44 kilograms became extinct in the Late Pleistocene. Although most were marsupials, the list includes the large, flightless mihirung Genyornis newtoni. More than 700 dates onGenyornis eggshells from three different climate regions document the continuous presence of Genyornis from more than 100,000 years ago until their sudden disappearance 50,000 years ago, about the same time that humans arrived in Australia. Simultaneous extinction of Genyornis at all sites during an interval of modest climate change implies that human impact, not climate, was responsible.  相似文献   

Killer whale predation on sea otters linking oceanic and nearshore ecosystems   总被引：2，自引：0，他引：2  

JA Estes  MT Tinker  TM Williams  DF Doak 《Science (New York, N.Y.)》1998,282(5388):473-476

After nearly a century of recovery from overhunting, sea otter populations are in abrupt decline over large areas of western Alaska. Increased killer whale predation is the likely cause of these declines. Elevated sea urchin density and the consequent deforestation of kelp beds in the nearshore community demonstrate that the otter's keystone role has been reduced or eliminated. This chain of interactions was probably initiated by anthropogenic changes in the offshore oceanic ecosystem.  相似文献