Extinction and the Mammoth Steppe

Extinction and the Mammoth SteppeDuring the Pleistocene Ice Age that ended 12,000 years ago, many largemammals coexisted in an ecosystem that paleontologist Dale Guthrie dubbedthe “mammoth steppe,” an icy prairie too cold, windy, and dry to support morethan a few trees. When this ecosystem faded away at the end of the IceAge, many of its characteristic animals, like the mammoth, the woollyrhino, and the short-faced bear, went extinct, while a new set ofmegafauna – moose, elk, and bison – invaded Alaska and the Yukon. Tounderstand the varied fates of these big herbivores, Guthrie looks to theirdigestive systems.Which of the sentences below best expresses the essential information in thehighlighted sentence in the passage? Incorrect choices change the meaning inimportant ways or leave out essential information.A.Moose, elk, and bison replaced mammoths, woolly rhinos, andshort-faced bears as the ecosystem changed at the end of the Ice Age.B.Many of the animals of the Ice-Age ecosystem, including themammoth, the woolly rhino, and the short-faced bear, faded awaybecause a new set of megafauna invaded the area.C.Animals such as mammoth, the woolly rhino, and the short-facedbear were replaced by animals such as moose, elk, and bison as thecharacteristic megafauna of the Ice Age.D.When new megafauna species such as moose, elk, and bisoninvaded Alaska and the Yukon, this ecosystem faded away.Any creature that lives off leaves or stems must overcome an arrayof defenses to absorb the nutrients inside. Many plants produce toxinsdesigned to discourage herbivores – and the longer the vegetation grows, themore poisonous it gets. Even the youngest, freshest buds and leaves are full ofcellulose, the complex sugar that builds plants’ cell walls. Only bacteria areable to break down cellulose, so every herbivore from rabbit to elephant hasevolved ways to nurture cellulose-digesting bacteria in its gut. Wild ruminantslike bison and moose ferment (breakdown) their food in a large forestomachcalled the rumen. [▇] Inside this chamber, microbes tear apart plant cells andreconstruct their contents into a complete nutritional package that includesevery B vitamin and every essential amino acid. [▇] Because they fermenttheir food before it reaches their intestines, ruminants can eat toxic plants thatwould sicken or kill a horse. [ ▇ ] However, their digestion is slow bycomparison – and because of the way their guts are designed, it cannot besped up. [▇]The word “an array of” in the passage is closest in meaning toA.variousB.strongC.tinyD.well-developedAccording to paragraph 2, what do all herbivores have in common?A.They digest their food relatively slowly.B.They can eat plants that produce different kinds of toxins.C.They ferment their food before it reaches their intestines.D.They all need bacteria to break down cellulose.According to paragr...