下列各项属于主观臆想联系的是()
A.江河污染影响人们的生活
B.核泄漏事故危及人类的生存
C.毁林导致生物物种的迅速减少
D.彗星出现预示将要发生战争
物种频度从高到低分A、B、C、D和E五级,其中属于E级频度的种类往往是()
A.优势种
B.伴生种
C.偶见种
D.残遗种
某一物种的个体样方数占全部样方数的百分比,这属于群落数量特征中的()
A.多度
B.密度
C.频度
D.优势度
According to the text, which of the following is true?
[A] the popularity of gap years results from an increasing number of charities.
[B] Prince William was working hard during his gap year.
[C] gap years are not as fashionable as they were ten years ago.
[D] a well-structured gap year is a guarantee of university success.
关于生物群落的描述,下列选项错误的是()
A.生物群落有时也可狭义地指某一分类单元物种数目的总和
B.生物群落为生态系统中生物成分的总和
C.每个生物群落都有一定的组成和营养结构
D.生物群落是任意物种的随意组合,生活在同一群落中的各个物种是通过长期历史发展和自然选择而保存下来的