問題詳情

Question 32-40Generally, in order to be preserved in the fossil record, organisms must possess hard body partssuch as shells or bones. Soft, fleshy structures are quickly destroyed by predators pr decayed bybacteria. Even hard parts left on the surface for and length of time will be destroyed Therefore,organisms must be buried rapidly to escape destruction by the elements and to be protected(5) agents of weathering and erosion Marine organisms thus are better candidates forfossilization than those living on the land because the ocean is typically the site of sedimentation,whereas the land is largely the site of erosion.The beds of ancient lakes were also excellent sites for rapid burial of skeletal remains offreshwater organisms and skeletons of other animals, including those of early humans Ancient(10)swamps were particularly plentiful with prolific growths of vegetation, which fossilized inabundance. Many animals became trapped in bogs overgrown by vegetation. The environment ofthe swamps kept bacterial decay to a minimum, which greatly (aideD)in the preservation of plantsand animals. The rapidly accumulating sediments in flood plains, deltas, and stream channelsburied freshwater organisms, along with other plants and animals that happened to fall into the(15)water.Only a small fraction of all the organisms that have ever lived are preserved as fossils. Normally,the remains of a plant or animal are completely destroyed through predation and decay. Althoughit seems that fossilization is common for some organisms, for others it is almost impossible. Forthe most part, the remains of organisms are recycled in the earth, which is fortunate because(20)otherwise soil and water would soon become depleted of essential nutrients. Also, most of thefossils exposed on Earth’s surface are destroyed by weathering processes. This makes for anincomplete fossil record with poor or no representation of certain species.The best fossils are those composed of unaltered remains. Generally, it is the inorganic hard parts,composed mostly of calcium carbonate, that form the vast majority of unaltered fossils. Calcite and(25)aragonite also contributed to a substantial number of fossils of certain organisms.
32. According to the passage, an organism without hard body parts
(A)is not likely to appear in the fossil record
(B)is not heavy enough to sink below the surface
(C)is not attractive to predators
(D)takes a long time to decay

參考答案

答案：A
難度：簡單0.8
統計：A(4),B(0),C(1),D(0),E(0)

內容推薦

內容推薦