托福official24综合写作生物学类Integrated Writing范文+题目解析

As much as we would like to have the remains of actual dinosaur tissue, there are sound reasons for being skeptical of the identifications made in the reading.First, the soft, flexible substance inside the bone channels isn't necessarily the remains of blood vessels. It is much more likely to be something else. Like what? You might say. Well, long after an organism is died, bacteria sometimes colonize hollows, empty areas in bones, like the channels that once held blood vessels. When bacteria lived inside bones, they often leave behind traces of organic material. What the researchers in the reading are identifying as blood vessels might just be traces of soft and moist residue left by bacteria colonies.All right. What about the iron-filled spheres? Well, the problem is that scientists found identical reddish spheres in fossils of other animals found in the same place. That includes fossils of primitive animals that did not have any red blood cells when they were alive. Clearly, if these spheres appear in organisms that did not have any red blood cells, then the spheres cannot be the remains of red blood cells. The spheres probably have a very different origin. They are probably just pieces of reddish mineral.Third, the collagen. The problem is that we have never found collagen in animal remains that are older than one hundred thousand years. Collagen probably cannot last longer than that. Finding collagen from an animal that lived seventy million years ago would really contradict our ideas about how long collagen can last. It is just too improbable. The most likely explanation for the presence of collagen is that it doesn't come from the T. rex, but from another much more recent source. For example, human skin contains collagen, so the collagen may have come from the skin of the researchers who are handling the bone.