题干

在烧杯中加入一定量的枯草浸出液,烧杯中的枯草杆菌以其中的有机物为食.过几天后放入大草履虫,再过一段时间后,放入双小核草履虫,它们均以枯草杆菌为食.三种生物在浸出液中数量的增减情况如图所示,据图分析错误的是(  )

A:枯草杆菌和草履虫之间构成捕食关系,两种草履虫之间构成竞争关系

B:a、b两条曲线分别表示枯草杆菌和双小核草履虫的数量变化情况

C:烧杯内混合培养的每一种生物,均存在种内斗争

D:经过足够长的时间后,a、b两条曲线最终趋向动态平衡

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D

同类题2

    More than 2.25 billion cups of coffeeare consumed across the globe each day, and it's likely that many taste bitter.

    Now, a new study suggests that coffeefans can make their drink taste sweeter by simply changing the color of theircups.

Scientists claim that blue and glass mugs,which are popular in some coffee shops, can reduce coffee's bitterness, withoutany need for sugar, and that coffee drunk from white cups tastes the bitterest.

    To prove their claims, the researchersinvited 36 volunteers and used three different colored cups— blue, white andtransparent glass—to do an experiment.

    In the experiment, coffee consumed fromthe white cup was found to taste less sweet when compared to the other twocolored cups, while the blue cup made the coffee taste the sweetest.

    The scientists believe that the colorbrown may be associated with coffee's bitterness because coffee in a white cupappears the brownest and tastes the bitterest.

  “Our study clearly shows that the colorof a coffee cup does influence the perceived (感受到的) taste and flavor of coffee,” said DrGeorge Doorn of Federation University Australia, “but the potential effects maybe different between a one-time purchase and a return customer.”

  “Anyhow, the effect of the color of thecup on the flavor of the coffee suggests that café owners, baristas (服务员), aswell as coffee cup manufacturers should carefully consider the color of theircups, ” he added.

    However, the idea that color can alterthe taste of food and drink is not new.

    A study published last year revealedthat red, strawberry-flavored mousse (慕斯蛋糕) served on a white plate was rated as10 percent sweeter and 15 percent more flavorous than the same food presentedon a black plate.