broall
Only 1,000 to 2,000 species of fruit flies exist worldwide. Nowhere in the world are fruit flies more taxonomically diverse than in the Hawaiian islands, which host some 500 species. A subset of fruit flies called the picture-winged drosophilids is represented in Hawaii by 106 species. All of the fruit fly species now present in the Hawaiian archipelago are thought to be the descendants of the same one or two ancestral females.
Which one of the following can be inferred from the passage?
(A) All of the picture-winged drosophilids in Hawaii are believed to be the descendants of the same one or two ancestral female fruit flies.
(B) Picture-winged drosophilids are found only in the Hawaiian islands.
(C) All of the 1,000 to 2,000 species of fruit flies worldwide are believed to be the descendants of one or two females.
(D) If 500 new species of fruit flies were discovered, then Hawaiian fruit flies would no longer be the most taxonomically diverse
population.
(E) Some fruit flies originated in Hawaii and spread from there to other parts of the world.
Source: LSAT
We know three things:
1) There are 106 species of PWD in Hawaii.
2) PWDs are fruit flies.
3) All fruit flies in Hawaii are thought to be descended from the same 1 or 2 females
(A) Yep. PWDs are fruit flies, and all fruit flies in Hawaii are said to come from these ancestors.
(B) Though we know there are 106 species of PWDs in Hawaii, that doesn't mean there aren't 100 more somewhere else.
(C) This extrapolates out too far from the last sentence. We know this is true about all the fruit flies in Hawaii, not all the fruitflies in the world.
(D) This is an interesting one. There are about 500 species in Hawaii, so if, say, 600 species were found in another place, this answer would be true. However, 500 alone wouldn't be enough. ALSO (and more important), those 600 species would have to be found somewhere other than Hawaii.
(E) This goes into way more detail than the passage does. We don't know about the migrations of the fruit flies.