Reading passage:
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-miHion-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.
Essay:
The passage and the lecture are about the different materials found in fossils of the dinosour’s leg bone. The passage provide the information about several theories of remained materials of animal in the fossils. the lecture ,however, opposes the information provided in the passage.
First, the passage expalins about the branching canals found in a leg bone of the dinosour. These canals were filled with the organic materials which were once filled with the blood vessels. On the other hand, the lecture casts doubt on this by stating that the organic materials found in the canals are not the soft tissue. The bacteria colonized in the empty canal space and they left the trace of the organic material. Thus, this information of the lecture refutes the details of the passage.
Second, the passage states about presence of the iron into the bone sphere shows that once there were red blood cells. Iron is important to keep tissue vitalized by supply oxygen to it. On the contrary, the lecture claims that the presence of iron field doesn’t prove the presence of the red blood cells, as during that time no red blood cells were found in any other animals. So it can be a reddish mineral which shows a evidence of the iron. Hence, this point also contradicts the point made in the passage.
Lastly, the passage presents the evidence of presence of the collagen -a fibrous protein present in fossils, which is one of the component of the living bone tissue. Whereas, the lecture point out this evidence by stating that the fossil is 1700 years old. However, the collagen tissues can not last long more than 1000 years. So it can not be a recent human skin whoever handled it. Thus, this point made in the lecture also challenges the point made in the reading.
TOEFL listening discussions: Where does this conversation probably take place?