Science and Nature Critical Reading Practice Exercises Set 3

Science and Nature Critical Reading

Questions 1–9 are based on the following passage.

The following passage describes the composition and nature of ivory.

Ivory skin, ivory teeth, Ivory Soap, Ivory Snow—we hear "ivory" used all the time to describe something fair, white, and pure. But where does ivory come from, and what exactly is it? Is it natural or man-made? Is it a modifier, meaning something pure and white or is it a specialized and discrete substance?

Historically, the word ivory has been applied to the tusks of elephants. However, the chemical structure of the teeth and tusks of mammals is the same regardless of the species of origin, and the trade in certain teeth and tusks other than elephant is well established and widespread. Therefore, ivory can correctly be used to describe any mammalian tooth or tusk of commercial interest that is large enough to be carved or scrimshawed. Teeth and tusks have the same origins. Teeth are specialized structures adapted for food mastication. Tusks, which are extremely large teeth projecting beyond the lips, have evolved from teeth and give certain species an evolutionary advantage that goes beyond chewing and breaking down food in digestible pieces. Furthermore, the tusk can be used to actually secure food through hunting, killing, and then breaking up large chunks of food into manageable bits.

The teeth of most mammals consist of a root as well as the tusk proper. Teeth and tusks have the same physical structures: pulp cavity, dentine, cementum, and enamel. The innermost area is the pulp cavity. The pulp cavity is an empty space within the tooth that conforms to the shape of the pulp. Odontoblastic cells line the pulp cavity and are responsible for the production of dentine. Dentine, which is the main component of carved ivory objects, forms a layer of consistent thickness around the pulp cavity and comprises the bulk of the tooth and tusk. Dentine is a mineralized connective tissue with an organic matrix of collagenous proteins. The inorganic component of dentine consists of dahllite. Dentine contains a microscopic structure called dentinal tubules which are micro-canals that radiate outward through the dentine from the pulp cavity to the exterior cementum border. These canals have different configurations in different ivories and their diameter ranges between 0.8 and 2.2 microns. Their length is dictated by the radius of the tusk. The three dimensional configuration of the dentinal tubules is under genetic control and is therefore a characteristic unique to the order of the mammal.

Exterior to the dentine lies the cementum layer. Cementum forms a layer surrounding the dentine of tooth and tusk roots. Its main function is to adhere the tooth and tusk root to the mandibular and maxillary jaw bones. Incremental lines are commonly seen in cementum.

Enamel, the hardest animal tissue, covers the surface of the tooth or tusk which receives the most wear, such as the tip or crown. Ameloblasts are responsible for the formation of enamel and are lost after the enamel process is complete. Enamel exhibits a prismatic structure with prisms that run perpendicular to the crown or tip. Enamel prism patterns can have both taxonomic and evolutionary significance.

Tooth and tusk ivory can be carved into an almost infinite variety of shapes and objects. A small example of carved ivory objects are small statuary, netsukes, jewelry, flatware handles, furniture inlays, and piano keys. Additionally, wart hog tusks, and teeth from sperm whales, killer whales, and hippos can also be scrimshawed or superficially carved, thus retaining their original shapes as morphologically recognizable objects.

The identification of ivory and ivory substitutes is based on the physical and chemical class characteristics of these materials. A common approach to identification is to use the macroscopic and microscopic physical characteristics of ivory in combination with a simple chemical test using ultraviolet light.

1. In line 5, what does the term discrete most nearly mean?
   1. tactful
   2. distinct
   3. careful
   4. prudent
   5. judicious
2. Which of the following titles is most appropriate for this passage?
   1. Ivory: An Endangered Species
   2. Elephants, Ivory, and Widespread Hunting in Africa
   3. Ivory: Is It Organic or Inorganic?
   4. Uncovering the Aspects of Natural Ivory
   5. Scrimshaw: A Study of the Art of Ivory Carving
3. The word scrimshawed in line 12 and line 52 most nearly means
   1. floated.
   2. waxed.
   3. carved.
   4. sunk.
   5. buoyed.
4. Which of the following choices is NOT part of the physical structure of teeth?
   1. pulp cavity
   2. dentine
   3. cementum
   4. tusk
   5. enamel
5. As used in line 13, what is the best synonym for mastication?
   1. digestion
   2. tasting
   3. biting
   4. chewing
   5. preparation
6. Which sentence best describes dentinal tubules?
   1. Dentinal tubules are a layer surrounding the dentine of tooth and tusk roots.
   2. Dentinal tubules are micro-canals that radiate outward through the dentine from the pulp cavity to the exterior cementum border.
   3. Dentinal tubules are responsible for the formation of enamel and are lost after the enamel process is complete.
   4. Dentinal tubules cover the surface of the tooth or tusk which receives the most wear, such as the tip or crown.
   5. Dentinal tubules are extremely large teeth projecting beyond the lips that have evolved from teeth and give certain species an evolutionary advantage.
7. According to the passage, all of the following are organic substances EXCEPT
   1. cementum.
   2. dentine.
   3. dahllite.
   4. ameloblasts.
   5. collagen.
8. According to the passage, how can natural ivory be authenticated?
   1. by ultraviolet light
   2. by gamma rays
   3. by physical observation
   4. by osmosis
   5. by scrimshaw
9. According to the passage, which statement is NOT true of enamel?
   1. It is an organic substance.
   2. It is the hardest of animal tissues.
   3. It should never be exposed to ultraviolet light.
   4. It structure is prismatic.
   5. It is formed with the aid of ameloblasts.

Questions 10–18 are based on the following passage.

This passage is about the process by which scientists prove theories, the scientific method.

The scientific method usually refers to either a series or a collection of processes that are considered characteristic of scientific investigationand of the acquisition of new scientific knowledge.

The essential elements of the scientific method are:

Observe: Observe or read about a phenomenon.

Hypothesize:Wonder about your observations, and invent a hypothesis, or a guess, which could explain the phenomenon or set of facts that you have observed.

Test: Conduct tests to try out your hypothesis.

Predict: Use the logical consequences of your hypothesis to predict observations of new phenomena or results of new measurements.

Experiment: Perform experiments to test the accuracy of these predictions.

Conclude: Accept or refute your hypothesis.

Evaluate: Search for other possible explanations of the result until you can show that your guess was indeed the explanation, with confidence.

Formulate new hypothesis: as required.

This idealized process is often misinterpreted as applying to scientists individually rather than to the scientific enterprise as a whole. Science is a social activity, and one scientist's theory or proposal cannot become accepted unless it has been published, peer reviewed, criticized, and finally accepted by the scientific community.

Observation

The scientific method begins with observation. Observation often demands careful measurement. It also requires the establishment of an operational definition of measurements and other concepts before the experiment begins.

Hypothesis

To explain the observation, scientists use whatever they can (their own creativity, ideas from other fields, or even systematic guessing) to come up with possible explanations for the phenomenon under study. Deductive reasoning is the way in which predictions are used to test a hypothesis.

Testing

In the twentieth century, philosopher Karl Popper introduced the idea that a hypothesis must be falsifiable; that is, it must be capable of being demonstrated wrong. A hypothesis must make specific predictions; these predictions can be tested with concrete measurements to support or refute the hypothesis. For instance, Albert Einstein's theory of general relativity makes a few specific predictions about the structure of space and flow of time, such as the prediction that light bends in a strong gravitational field, and the amount of bending depends in a precise way on the strength of the gravitational field. Observations made of a 1919 solar eclipse supported this hypothesis against other possible hypotheses, such as Sir Isaac Newton's theory of gravity, which did not make such a prediction. British astronomers used the eclipse to prove Einstein's theory and therefore, eventually replaced Newton's theory.

Verification

Probably the most important aspect of scientific reasoning is verification. Verification is the process of determining whether the hypothesis is in accord with empirical evidence, and whether it will continue to be in accord with a more generally expanded body of evidence. Ideally, the experiments performed should be fully described so that anyone can reproduce them, and many scientists should independently verify every hypothesis. Results that can be obtained from experiments performed by many are termed reproducible and are given much greater weight in evaluating hypotheses than non-reproducible results.

Evaluation

Falsificationism argues that any hypothesis, no matter how respected or time-honored, must be discarded once it is contradicted by new reliable evidence. This is, of course, an oversimplification, since individual scientists inevitably hold on to their pet theory long after contrary evidence has been found. This is not always a bad thing. Any theory can be made to correspond to the facts, simply by making a few adjustments—called "auxiliary hypothesis"—so as to bring it into correspondence with the accepted observations. The choice of when to reject one theory and accept another is inevitably up to the individual scientist, rather than some methodical law.

Hence all scientific knowledge is always in a state of flux, for at any time new evidence could be present[ed] that contradicts long-held hypotheses.

The experiments that reject a hypothesis should be performed by many different scientists to guard against bias, mistake, misunderstanding, and fraud. Scientific journals use a process of peer review, in which scientists submit their results to a panel of fellow scientists (who may or may not know the identity of the writer) for evaluation. Peer review may well have turned up problems and led to a closer examination of experimental evidence for many scientists. Much embarrassment, and wasted effort worldwide, has been avoided by objective peer review, in addition to continuing the use and proving the necessity of the scientific method.

10. Which step in the process of scientific method do lines 63–72 speak of?
    1. operational definition
    2. verification
    3. evaluation
    4. phenomenon
    5. hypothesizing
11. What is the tone of this passage?
    1. enigmatic
    2. apathetic
    3. abstruse
    4. instructive
    5. revealing
12. In line 63 the word falsificationism most nearly means
    1. validation.
    2. qualification.
    3. confirmation.
    4. facilitation.
    5. refutation.
13. Which statement is FALSE?
    1. Reproducible results can be obtained by experiments performed by a variety of scientists.
    2. An auxiliary hypothesis can be made to correspond to the facts.
    3. Einstein's theory of relativity makes space and time predictions.
    4. Peer review is usually not a valuable tool for scientists.
    5. Experiments are a necessary element in the scientific method.
14. According to the passage, which is true of a hypothesis?
    1. It is not a necessary process in the scientific method.
    2. It cannot be discarded by a competing theory.
    3. It is a guess.
    4. It can make a broad and general prediction.
    5. It is always considered auxiliary.
15. What is the best title for this passage?
    1. The Theory of Relativity
    2. The Scientific Method: A Step-by-Step Process
    3. The Two Stages of Proving Theories
    4. How to Form a Hypotheses
    5. Evaluating Data with the Scientific Method
16. What is meant by the term operational definition in line 28 of the passage?
    1. a scientific law
    2. a theory
    3. a clear definition [of a measurement]
    4. scientific method
    5. hypothesis
17. What do lines 37–48 of the passage indicate?
    1. The theory of general relativity is a hypothesis.
    2. The theory of general relativity is a hypothesis.
    3. Einstein was the father of the scientific method.
    4. Space and the flow of time theories are still in a state of flux.
    5. Sir Isaac Newton's theory of gravity disproved Einstein's theory.
18. Which is NOT a step used in the process of scientific method?
    1. observation
    2. simplification
    3. evaluation
    4. verification
    5. hypothesize