Endotherms are animals such as modern birdsand mammals that keep their body temperatures constant. For instance, humansare endotherms and maintain an internal temperature of 37℃, no matterwhether the environment is warm or cold. Because dinosaurs were reptiles, andmodern reptiles are not endotherms, it was long assumed that dinosaurs were notendotherms. However, dinosaurs differ in many ways from modern reptiles, andthere is now considerable evidence that dinosaurs were, in fact, endotherms.
One reason for believing that dinosaurswere endotherms is that dinosaur fossils have been discovered in Polar Regions.Only animals that can maintain a temperature well above that of the surroundingenvironment could be active in such cold climates.
Legposition and movement
There is a connection between endothermyand the position and movement of the legs. The physiology of endothermy allowssustained physical activity, such as running. But running is efficient only ifan animal’s legs are positioned underneath its body, not at the body’s side, asthey are for crocodiles and many lizards. The legs of all modern endotherms areunderneath the body, and so were the legs of dinosaurs. This strongly suggeststhat dinosaurs were endotherms.
There is also a connection betweenendothermy and bone structure. The bones of endotherms usually includestructures called Haversian canals. These canals house nerves and blood vesselsthat allow the living animal to grow quickly; and rapid body growth is in facta characteristic of endothermy. The presence of Haversian canals in boneis astrong indicator that the animal is an endotherm, and fossilized bones ofdinosaurs are usually dense with Haversian canals.
- Main point: 恐龙是恒温动物
- Sub point 1: 恐龙的化石在极地发现，而极地只有恒温动物生存，所以恐龙是恒温动物。
- Sub point 2: 恐龙有跟恒温动物一样的腿结构，所以恐龙是恒温动物。(这个是有逻辑漏洞
- Sub point 3: 恐龙跟恒温动物一样的哈弗森管，所以恐龙是恒温动物。
Many scientists have problems with thearguments you read in the passage. They don’t think those arguments prove thatdinosaurs were endotherms.
Take the polar dinosaur argument. Whendinosaurs lived, even the Polar Regions, where dinosaur fossils have beenfound, were much warmer than today, warm enough during part of the year for animalsthat were not endotherms to live. And during the months when the Polar Regionswere cold, the so-called polar dinosaurs could have migrated to warmer areas orhibernated like many modern reptiles do. So the presence of dinosaur fossils inPolar Regions doesn’t prove the dinosaurs were endotherms.
Well, what about the fact those dinosaurshave their legs placed under their bodies, not out to the side like crocodiles.That doesn’t necessarily mean dinosaurs were high-energy endotherms built forrunning. There is another explanation for having legs under the body. This bodystructure supports more weight, so with the legs under their bodies, dinosaurscan grow to a very large size.
Being large had advantages for dinosaurs,so we don’t need the idea of endothermy and running to explain why dinosaursevolved to have their legs under their bodies.
那么，恐龙的腿在身体下方而不是两侧是怎么回事呢?这个是不足以证明恐龙是可以进行奔跑类剧烈运动的恒温动物。腿生长在身体下部对于恐龙是别有的意义的。这样的结构可以支撑更多的重量。所以腿长在身体下部可以让恐龙长到非常大。对于恐龙来说，巨大的重量是非常有意义的，所以没有比用要用恒温动物和奔跑来解释为什么恐龙进化出这样的身体结构的。Ok, so how about bone structure? Many dinosaur bones do haveHaversian canals, and that is true.
The dinosaur bones also have growth rings.Growth rings are thickening of the bone that indicates periods of time when thedinosaurs weren’t rapidly growing. These growth rings are evidence that dinosaursstopped growing or grew more slowly during cooler periods. This pattern ofperiodic growth, you know, rapid growth followed by no growth or slow growth,and then rapid growth again, is characteristic of animals that are notendotherms. Animals that maintain a constant body temperature year-round astrue endotherms do grow rapidly even when the environment becomes cool.
Sub point one: warmer, migrated,hibernated
Sub point two: doesn’t necessarily, forrunning, more weight, advantages
Sub point three: Haversian canals, growthring, slowly or stop V.S. rapid, periodic
The professor actually contradicts thestatements made in the passage. She is of the view that dinosaurs are notendotherms i.e. they were not able to keep their body temperature at a constantrate. The professor contradicts the issue of dinosaurs being endothers based onthe availability of fossils being available in thwe polar regions, she say thatthe polar regions in those days were not as cold as they are today i.e at leastwarm enough for dinosaurs to live. During harsh winters she says that there isa possibility of the dinosaurs actually migrating to warmer regions. The issueof leg position and movement being used as a reason to classify the dinosaursas endotherms does not please the professor either. She says that dinosaurs hadlegs under their bodies to support their huge bodies i.e the legs under thebody of the dinosaur were actually to support the huge weight of the dinosaurand not to provide it with a body structure like endotherms(which is actuallysuited for running).
The professor acknowledges the presence ofhaversian canals but also points out that that the fossils show the presence ofgrowth rings. These rings occur due to the thickening of the bone. Thethickening indicates that the dinosaurs were’nt actually growing continuouslybut were experiencing periods of rapid growth and periods of no growth insuccesion. This pattern. she says is characteristic of non-endothermicaanimals.
Thus it can be inferred that the professorchallenges the passage by giving reasons as to why she thinks that the dinosauris not an endotherm.
Description of Response:
Despite initial appearances, this responselargely succeeds in clearly and accurately presenting how the lecture points takeissue with the points in the reading passage that dinosaurs were endotherms.The first point regarding dinosaurs in polar regions could be a bit clearer.Otherwise, the response mainly suffers from typographical errors, but these arenot regarded as major problems; it is obvious that the writer has good controlof structure and vocabulary and the ability to use these to convey in anorganized and logical manner what has been understood and asked.