以下是
Animal fossils usually provide very little opportunity to study the actual animal tissues, because in fossils the animals' living tissues have been largely replaced by minerals. Thus, scientists were very excited recently when it appeared that a 70-million-year-old fossil of Tyrannosaurus rex (T. rex), a dinosaur, might still contain remains of the actual tissues of the animal. The discovery was made when researchers deliberately broke open the T. rex’s leg bone, thereby exposing its insides to reveal materials that seem to be remains of blood vessels, red blood cells, and collagen matrix.
First, the breaking of the fossilized leg bone revealed many small branching channels inside, which probably correspond to hollows in the bones where blood vessels were once located. The exciting finding was the presence of a soft, flexible organic substance inside the channels. This soft substance may very well represent the remains of the actual blood vessels of T. rex.
Second, microscopic examination of the various parts of the inner bone revealed the presence of spheres that could be the remains of red blood cells. Tests showed that the spheres contained iron-a material vital to the role of red blood cells in transporting oxygen to tissues. Moreover, the spheres had dark red centers (substances with iron tend to be reddish in color) and were also about the size of red blood cells.
Third, scientists performed a test on the dinosaur leg bone that showed that it contained collagen. Collagen is a fibrous protein that is a main component of living bone tissue, in which it forms a so-called collagen matrix. Collagen (or its chemical derivatives) is exactly the kind of biochemical material that one would expect to find in association with bone tissue.
Summarize the points made in the lecture, being sure to explain how they support/contradict specific points made in the reading passage.
网老师提醒：用TPO作为托福备考教材和练习工具，已经成为全球考生必选。由于TPO试题的权威性和实用性，SmartStudy(网)组织了权威师资对TPO进行了逐套逐项逐题的详细讲读，包括题目理解，答题思路，解题步骤，答案分析和难点重点针对解析，覆盖最全面的做题逻辑，输出细致贴心的答题辅导，并以精美的课件清晰呈现。相信SmartStudy(网)托福版块的“TPO逐题精讲”能有效帮助您查漏补缺，完美备考。
版权声明：本文系网独家稿件，版权为网所有。转载须注明来源及作者，否则必将追究法律责任。