- Conodonts, the spiky phosphatic remains (bones and teeth composed of calcium phosphate) of tiny marine animals that probably appeared about 520 million years ago, were once among the most
- controversial of fossils. Both the nature of the organism to which the remains belonged and the function of the remains were unknown. However, since the 1981 discovery of fossils preserving not just the phosphatic elements but also other remains
- of the tiny soft-bodied animals (also called conodonts) that bore them, scientists' reconstructions of the animals' anatomy have had important implications for hypotheses concerning the development of the vertebrate skeleton.
- The vertebrate skeleton had traditionally been regarded as a defensive development, champions of this view postulating that it was only with the much later evolution of jaws that vertebrates became predators. The first vertebrates, which were soft-
- bodied, would have been easy prey for numerous invertebrate carnivores, especially if these early vertebrates were sedentary suspension feeders. Thus, traditionalists argued, these animals developed coverings of bony scales or plates, and teeth were
- secondary features, adapted from the protective bony scales. Indeed, external skeletons of this type are common among the well-known fossils of ostracoderms, jawless vertebrates that existed from approximately 500 to 400 million years ago.
- However, other paleontologists argued that many of the definitive characteristics of vertebrates, such as paired eyes and muscular and skeletal adaptations
for active life, would not have evolved unless the
- first vertebrates were predatory. Teeth were more primitive than external armor according to this view, and the earliest vertebrates were predators.
- The stiffening notochord along the back of the body, V-shaped muscle blocks along the sides,
- and posterior tail fins help to identify conodonts as among the most primitive of vertebrates. The lack of any mineralized structures apart from the elements in the mouth indicates that conodonts were more primitive than the armored jawless fishes such as the
- ostracoderms. It now appears that the hard parts that first evolved in the mouth of an animal improved its efficiency as a predator, and that aggression rather than protection was the driving force behind the origin of the vertebrate skeleton.
1. According to the passage, the anatomical evidence provided by the preserved soft bodies of conodonts led scientists to conclude that
A. conodonts had actually been invertebrate carnivores
B. conodonts' teeth were adapted from protective bony scales
C. conodonts were primitive vertebrate suspension feeders
D. primitive vertebrates with teeth appeared earlier than armored vertebrates
E. scientists' original observations concerning the phosphatic remains of conodonts were essentially correct
2. The second paragraph in the passage serves primarily to
A. outline the significance of the 1981 discovery of conodont remains to the debate concerning the development of the vertebrate skeleton
B. contrast the traditional view of the development of the vertebrate skeleton with a view derived from the 1981 discovery of conodont remains
C. contrast the characteristics of the ostracoderms with the characteristics of earlier soft-bodied vertebrates
D. explain the importance of the development of teeth among the earliest vertebrate predators
E. present the two sides of the debate concerning the development of the vertebrate skeleton
3. It can be inferred that on the basis of the 1981 discovery of conodont remains, paleontologists could draw which of the following conclusions?
A. The earliest vertebrates were sedentary suspension feeders.
B. Ostracoderms were not the earliest vertebrates.
C. Defensive armor preceded jaws among vertebrates.
D. Paired eyes and adaptations for activity are definitive characteristics of vertebrates.
E. Conodonts were unlikely to have been predators.
1. Does "According to the passage" always mean the author's point of view?
2. What should have been the strategy in Q1? First locate where conclusions are mentioned in the passage and then eliminate conclusions one by one or Read each ans. choice and locate where these conclusions are mentioned in the passage?
3. How did we conclude that ans. option D is the hypothesis the evidence led to? Why can't the traditional view be the hypothesis? These are just two sides right? Is there any weightage for why paleontologists' view was chosen as the hypothesis of scientists?
1) Yes. "According to the passage" questions should be answered from the point of view of the author.
2) Locating the answer to the question is very important. After you have identified the location, say, para 2, now you carefully eliminate each option based on what you have read. But do not get stuck in any question. If it's taking you a lot of time to select an answer, go with your gut feeling and mark an answer. Time spent on a question is not directly proportional to your accuracy. We need to accept that :)
3) The conclusion to ques 1 ie the evidence is mentioned in para 3. We get option D from para 3 as well. Para 3 supports other paleontologists who argued that these vertebrates were predators. We can boil down to option D from para 2 and para 3.
We cannot consider the traditional view as the hypothesis regarding new evidence.
para 1- Conodonts - one of the most controversial fossils, the discovery of the fossil of other remains-
- had important implications for hypotheses concerning the development of the vertebrate skeleton.
controversial fossil- two views presented.
Evidence supports which view? the latter. not the traditional view.