One species lives only in tree holes; another species lives only in streams.

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#Question id: 12340

#Section 1: Ecology

Keystone species are thought to have profound effects on the structure and composition of ecological communities because they

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#Question id: 4941

#Section 2: Evolution

Which of the factors below weaken the hypothesis of abiotic synthesis of organic monomers in early Earthʹs atmosphere?

1.  the relatively short time between intense meteor bombardment and appearance of the first life forms

2.  the lack of experimental evidence that organic monomers can form by abiotic synthesis

3.  Uncertainty about which gases comprised early Earthʹs atmosphere

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#Question id: 4619

#Section 2: Evolution

Within six months of effectively using methicillin to treat S. aureus infections in a community, all new S.aureus infections were caused by MRSA. How can this best be explained?

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#Question id: 12327

#Section 1: Ecology

Which  of  the  following  is  the  most  accepted hypothesis as  to  why  invasive  species  take  over  communities into which they have been introduced?

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#Question id: 4590

#Section 2: Evolution

Which of the following statements describe evolution?