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.
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.
In the reading passage, it talks about the fossils related to animal tissues, however, the professor holds different ideas.
To begin with, in the reading material, we learn that the lots of tiny branching channels are found inside of the leg bone fossil. The reading material argues that soft tissue is expected to be found in the channels. However, the professor thinks that the channels are more likely to be left by bacteria. In addition, in the reading passage, it talks about that spheres are found in inner bone and red blood cells can be remained. And in the reading passage, it gives evidence that the sphere have red centers. However the professor indicates that there is no evidence show that creature at that time had red cells and the red centers should be something else.
As a final point, in the reading passage, it talks about that collagen is found on the leg bone. Collagen is actually a biochemical material, which is expected to be an association with bone tissue.
However, the professor says that collagen is not likely to live as long as 7 million year. It may be some recent material. For instant, it may be from the hand skin of the researchers. In conclusion the professor does not agree with the reading passage.
TPO 25 In 1938 an archaeologist in Iraq acquired a Your reading says that these vessels were not set of clay jars that had been excavated two years earlier by villagers constructing a railroad line. The vessel was about 2,200 years old. Each clay jay contained a copper cylinder surrounding an iron rod. The archaeologist proposed that vessel were ancient electric batteries and even demonstrated that they can produce a small electric current when filled with some liquids. However, it is not likely that the vessels were actually used as electric batteries in ancient times. First of all, if the vessels were used as batteries, they would probably have been attached to some electricity conductors such as metal wires. But there is no evidence that any metal wires were located near the vessels. All that has been excavated are the vessels themselves. Second, the copper cylinders inside the jars look exactly like copper cylinders discovered in the ruins of Seleucia, an ancient city located nearby. We know that the copper cylinders from Seleucia were used for holding scrolls of sacred texts, not for generating electricity. Since the cylinders found with the jars have the same shape, it is very likely they were used for holding scrolls as well. That no scrolls were found inside the jars can be explained by the fact that the scrolls simply disintegrated over the centuries. Finally, what could ancient people have done with the electricity that the vessels were supposed to have generated? They had no devices that replied on electricity. As batteries, the vessels would have been completely useless to them. used as batteries in ancient times, but the arguments used in the reading are not convincing. The battery explanation could very well be correct. First, about the absence of wires or other conductors, Remember, vessels were discovered by local people, not archaeologists. These people might have found other material located near the jars. But since they were not trained archaeologists, they may not have recognized the importance of that material. So materials serving as wires or conductors might have been overlooked as uninteresting or even thrown away. We’ll never know. Second, it is true that the copper cylinders in the vessels are similar to cylinders used to hold scrolls, but that does not really prove anything. It’s possible that the copper cylinders were originally designed to preserve scrolls. And that some ancient inventor later discovered that if you use them together with iron rods and some liquid in a clay vessel, they will produce electricity. That’s how the first ancient battery could have been born. In other words, the copper cylinders could have been originally used for one purpose, but then adapted for another purpose. Finally, there’s the question of the possible uses of the battery in the ancient world. Well, the battery could produce a mild shock or tingling sensation when someone touched it. This could very well have been interpreted as evidence of some invisible power. You can easily see how people could convince others that they had magical powers through the use of the battery. Also, the battery could have been used for healing. Modern medicine uses mild electric current to stimulate muscles and relieve aches and pains. Ancient doctors may have used the batteries for the same purpose.
In the reading material, the author states that the vessels found in Iraq in 1938 were not actually used as electric batteries in ancient times. However in the listening material, the professor refutes that the argument is unconvincing as it was used as batteries.
First, according to the reading passage, the author suggests that if they were used as batteries, they would have been attached to some electricity conductors. However in the listening, the professor claims that we should remember that the discovery was made by local people along with some other materials. As they were not trained as archaeologist, they could not recognize the importance of some certain excavations.
Perhaps they were overlook as something uninterested and then thrown away. Second, the author in the reading material mentions that the vessels were likely used for holding scrolls. Unfortunately the professor argues that it could not prove anything. It is possible that the vessels may be originally designed to scrolls. However ancient inventor then discovered that if the vessels were used with iron rod and some liquid, it could generate the electricity. So the copper cylinders may be originally used for one purpose but adapted for another purpose.
Finally, the author of the reading passage asserts that the vessels would have been completely useless to ancient people as they had no devices that replied on electricity. In the contrary in obviously contradicts with the listening passage in which the professor contends that the battery could generate some mild shock and this also interprets evidence of some invisible power that how people convince others they had the magic power. Also it could be used for healing. In modern society doctors would use batteries to stimulate muscles and release pains. In ancient times people could also do that.
In conclusion, according to the listening material, the argument that the vessels could not be used as batteries is unwarranted.
TPO 26
The zebra mussel, a freshwater shellfish native to Eastern Europe, has long been spreading out from its original habitats and has now reached parts of North America. There are reasons to believe that this invasion cannot be stopped and that it poses a serious threat to freshwater fish populations in all of North America.
First, the history of the zebra mussel's spread suggests that the invasion might be unstoppable. It is a prime example of an invasion made possible by human transportation. From the zebra mussel’s original habitats in Eastern Europe, ships helped spread it out along new canals built to connect Europe’s waterways. The mussel can attach itself to a ship’ s bottom or can survive in the water—called \"ballast water\"—that the ship needs to take on to properly balance its cargo. By the early nineteenth century, the mussel had spread to the whole of Europe. It was later carried to the east coast of North America in the ballast water of ships traveling from Europe. The way ships have spread the zebra mussel in the past strongly suggests that the species will soon colonize all of North America.
Moreover, once zebra mussels are carried to a new habitat, they can dominate it. They are a hardy species that does well under a variety of conditions, and they have a high rate of reproduction. Most important, however, zebra mussels often have no predators in their new habitats, and species without natural predators are likely to dominate their habitats. Finally, zebra mussels are likely to cause a decline in the overall fish population in habitats where they become dominant. The mussels are plankton eaters, which means that they compete for food with many freshwater fish species. Contrary to what you just read, there are ways to control the zebra mussel's spread. What's more, it is not so clear that the mussel is a serious threat to fish populations.
True, the spread of zebra mussels couldn't be controlled in the past, but that's because people didn't have enough knowledge. In fact, there are effective ways to stop ships from carrying the mussels to new locations. Here's an example. The way zebra mussels usually travel across the ocean is that a ship takes on some fresh \"ballast water\" in Europe and then empties that water into American waterways when it arrives. Full of zebra mussels, but the ship can be required to empty out the freshwater and refill with ocean water while still out in the ocean. Salt water will kill the mussels.
Second, it's true that zebra mussels often don't have predators in their new habitats, but that's only in the beginning. What's been happening in Europe is that local aquatic birds sooner or later notice there's a new food source around and change their habits to exploit it. They switch from whatever they were eating before to eating zebra mussels. And birds can eat a lot of mussels. So zebra mussels aren't so likely to dominate their new habitats after all.
Finally, even in habitats where zebra mussels become dominant, is the overall fish population likely to decrease. It's true that zebra mussels may have a negative impact on fish that eat plankton. But on other fish, they can have a positive impact. For example, the mussels generate nutrients that are eaten by fish that feed near the bottom of the lake or river. So bottom-feeding fish populations may increase, even if plankton-eating fish population decrease.
Contrary to what is argued in the passage, the lecture illustrates how zebra mussels are not likely to become a serious threat to freshwater fish populations in North America.
First and foremost, new knowledge of the zebra mussel has shed light on new ways to prevent their invasion, even though people in the past have not been able to stop the spread of zebra mussels effectively. For instance, although a large amount of zebra mussels spread to North America by staying in the ballast water of a ship, people can now get rid of them before the ship gets to the shore – if the ballast water is emptied halfway of the journey and refreshed with sea water, the zebra mussels can be exterminated as soon as they get exposed to salt water.
Furthermore, zebra mussels are not likely to dominate a new habitat for a long period of time. The lecture agrees that zebra mussels may have no predators and reproduce rapidly in the beginning, but it would not be long before predators notice this new source of food and therefore prevent its domination.
Finally, zebra mussels would not cause the decline of overall fish population. While zebra mussels would most likely cause the decline of plankton eaters, as the passage suggests, they would also provide nutrients for bottom-feeding fish and eventually cause the population of those fish to increase.
TPO 33
Carved stone balls are a curious type of artifact found at a number of |locations in Scotland. They date from the late Neolithic period, around 4,000 years ago. They are round in shape; they were carved from several types of stone; most are about 70 mm in diameter; and many are ornamented to some degree. Archaeologists do not agree about their purpose and meaning, but there are several theories.
One theory is that the carved stone balls were weapons used in hunting or fighting. Some of the stone balls have been found with holes in them, and many have grooves on the surface. It is possible that a cord was strung through the holes or laid in the grooves around the ball. Holding the stone balls at the end of the cord would have allowed a person to swing it around or throw it.
A second theory is that the carved stone balls were used as part of a primitive system of weights and measures. The fact that they are so nearly uniform in size - at 70 mm in diameter-suggests that the balls were interchangeable and represented some standard unit of measure. They could have been used as standard weights to measure quantities of grain or other food, or anything that needed to be measured by weight on a balance or scale for the purpose of trade.
A third theory is that the carved stone balls served a social purpose as opposed to a practical or utilitarian one. This view is supported by the fact that many stone balls have elaborate designs. The elaborate carving suggests that the stones may have marked the important social status of their owners.
None of the three theories presented in the reading passage are very convincing.
First, the stone balls as hunting weapons, common Neolithic weapons such as arrowheads and hand axes generally show signs of wear, so we should expect that if the stone balls had been used as weapons for hunting of fighting, they too would show signs of that use. Many of the stone balls would be cracked or have pieces broken off. However, the surfaces of the balls are generally well preserved, showing little or no wear or damage.
Second, the carved stone balls maybe remarkably uniform in size, but their masses vary too considerably to have been used as uniform weights. This is because the stone balls were made of different types of stone including sandstone, green stone and quartzite. Each type of stone has a different density. Some types of stone are heavier than others just as a handful of feathers weighs less than a handful of rocks. Two balls of the same size are different weights depending on the type of stone they are made of. Therefore, the balls could not have been used as a primitive weighing system.
Third, it's unlikely that the main purpose of the balls was as some kind of social marker. A couple of facts are inconsistent with this theory. For one thing, while some of the balls are carved with intricate patterns, many others have markings that are extremely simple, too simple to make the balls look like status symbols. Furthermore, we know that in Neolithic Britain, when someone died, particularly a high-ranking person, they were usually buried with their possessions. However, none of the carved stone balls have been actually found in tombs or graves. That makes it unlikely that the balls were personal possessions that marked a person's status within the community.
The author in the reading passage explores three major functions of the carved stone balls. However, in the lecture, the professor respectively contradicts all his assertions by using three specific points as supports.
First, even though the reading passage suggests that the stone balls were weapons because of the holes and grooves on their surface, the professor argues that the stone balls didn’t show signs of use, which means they are neither cracked nor broken and thus cannot be used as weapons.
Second, despite the statement in the reading passage that the stone balls were used as primitive weighing system due to their uniform size, the professor contends that their masses vary too considerably from each other. Therefore, the balls could not function as weighing system.
Third, the author asserts that the stone balls served a social purpose owing to their elaborate designs while the professor proves that this claim is indefensible by pointing out that the balls were carved with not only intricate patterns but also simple ones, besides, none of the balls were found in the ancient tombs or graves. Consequently, it’s impossible that the balls were social markers.
TPO 34
A huge marine mammal known as Steller’s sea cow once lived in the waters around Bering Island off the coast of Siberia. It was described in 1741 by Georg W. Steller, a naturalist who was among the first European to see one. In 1768 the animal became extinct. The reasons for the extinction are not clear. Here are three theories about the main cause of the extinction.
First, the sea cows may have been overhunted by groups of native Siberian people. If this theory is correct, then the sea cow population would have originally been quite large, but hundreds of years off too much hunting by the native people diminished the number of sea cows. Sea cows were a good source of food in a harsh environment, so overhunting by native people could have been the main cause of extinction.
Second, the sea cow population may have become extinct because of ecosystems disturbances that caused a decline in their main source of food, kelp (a type of sea plant). Kelp populations respond negatively to a number of ecological changes. It is possible that ecological changes near Bering island some time before 1768 caused a decrease of the kelp that the sea cows depend on.
Third, the main cause of extinction of the sea cows could have been European fur traders who came to the island after 1741. It is recorded that the fur traders caught the last sea cow in 1768. It thus seems reasonable to believe that hunting by European fur traders, who possessed weapons that allowed them to quickly kill a large number of the animals, was the main cause of the sea cow’s extinction. Now I want to tell you about what one company found when it decided that it would turn over some of its new projects to teams of people, and make the team responsible for planning the projects and getting the work done. After about six months, the company took a look at how well the teams performed. On virtually every team, some members got almost a “free ride”… they didn’t contribute much at all, but if their team did a good job, they nevertheless benefited from the recognition the team got. And what about group members who worked especially well and who provided a lot of insight on problems and issues? Well … the recognition for a job well done went to the group as a whole, no names were named. So it wont surprise you to learn that when the real contributors were asked how they felt about the group process, their attitude was just the opposite of what the reading predicts.
Another finding was that some projects just didn’t move very quickly. Why? Because it took so long to reach consensus; it took many, many meetings to build the agreement among group members about how they would move the project along. On the other hand, there were other instances where one or two people managed to become very influential over what their group did. Sometimes when those influencers said “that will never work” about an idea the group was developing, the idea was quickly dropped instead of being further discussed. And then there was another occasion when a couple influencers convinced the group that a plan of theirs was “highly creative.” And even though some members tried to warn the rest of the group that the project was moving in directions that might not work, they were basically ignored by other group members. Can you guess the ending to this story? When the project failed, the blame was placed on all the members of the group.
The writer and the professor all talk about the possible reasons for the extinction of sea cows. While the passage raises three theories about the main cause of the extinction, the lecture has differing views.
According to the author, sea cows may have been over hunted by groups of native Siberian people, which could have been the main cause of the extinction. Not as the author puts it, the professor argues that over hunting for food could not be the main cause. He mentions that the sea cow was such a massive creature that could feed a small village for a month, and the population of native Siberian people was not very large. So, it was unlikely the native people hunted too much sea cow, the population of which would have originally been quite large.
In the passage, it is said that a decline in their main source of food,caused by ecosystems' disturbance, may be the second explanation. On the contrary, the lecture suggests that no real evidence indicated the sea cows had little kelp to eat. The ecosystems' disturbances really happened before 1768, but it caused other part of marine creatures decreased, not sea cows' main source of food, kelp.
At the points out the main cause could have been European fur traders, who were recorded catching sea cows. Quite the opposite, the speaker claims that it was not the real reason. Since the population was already small before Eropeanfur traders came to the island, there could have been something else decline a large number of the sea cows. And that is what the professor thinks the real reason of the extinction.
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