在线英语听力室_免费在线英语听力学习网站

This is Scientific American's 60-Second Science. I'm Adam Hinterthuer. Got a minute?

Farmers fertilize¹ their fields to get the maximum meal from their crops. But the effects of these loads of nitrogen and phosphorous extend beyond the field and past the growing season. According to a study published this week by the Proceedings² of the National Academy of Sciences, these nutrients⁴ can also drive the evolution of aquatic⁵ organisms. 

Agricultural fertilizers often drain into aquatic ecosystems⁶ and spur a frenzy⁷ of growth. Eventually the growth peaks and crashes as oxygen is consumed faster than it can be replenished⁸ - a condition called eutrophication. 

Using samples from two European lakes, Swiss researchers studied a century’s worth of eggs buried deep in the sediment⁹ by two species of Daphnia, a tiny crustacean¹⁰. They found that, during periods of high nutrient³ levels, genetically¹¹ distinct hybrid¹² species emerged. Those hybrids¹³ appeared better at surviving eutrophication and soon outnumbered the original species. 

What’s more, the hybrids remained the dominant¹⁴ Daphnia species decades after pollution control measures brought nutrient levels back to normal. The scientists say short-term human impacts can leave permanent changes in ecosystems and a species’ genetics. 

You could say we’ve got quite the ‘gene’ thumb.

Thanks for the minute for Scientific American's 60-Second Science. I'm Adam Hinterthuer.