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The authors of “The Development of the Concept of Electric Charge” emphasize the importance of ‘working hypotheses’ in scientific development. Explain, using examples from this case study, both how such hypotheses aid scientists in revealing new phenomena and how they might hinder scientists’ discovery of unexpected phenomena.

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Nelly Stracke
Nelly StrackeLv2
28 Sep 2019

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Related questions

QUESTION SET 3

Sexual Selection, Developmental Thresholds, and Ornamentation

INTRODUCTION

In Chapter 10 you read about how sexual selection can drive the evolution of bizarre and sometimes costly ornamentation or weaponry in animals, often in males. This paper reveals a situation where sexual selection is the driver, but the result is more complex than might be expected at first glance. The authors describe some beetle species where different thresholds encountered as larvae result in different levels of ornamentation, and consequently different reproductive strategies.

The authors show that in one family of beetles (the Scarabeidae [dung beetles]), two different threshold mechanisms have independently evolved. Each of these thresholds has a different effect on horn development in the males of these beetles. Both mechanisms are triggered by body size in larvae. For one mechanism, if a larva attains the threshold size its adult morphology (the phenotype it will have after it pupates) switches from being hornless to being horned. The second threshold, also based on larval body size, similarly results in either having a short or a long horn (see Figure 2).

This discovery led the authors to look more closely at other beetle species where male polymorphism was known to occur, and they found two other examples where this double threshold mechanism was operating (see Figure 1). In the family Lucanidae (stag beetles), they found that male trimorphism was characterized by differences in the mandibles, with male mandibles exhibiting three increasing sizes moderated by the thresholds. In the family Curculionidae (weevils), the thresholds controlled the development of ventral body spines. Here, the beetles either lacked spines (and thus resembled females), had short spines, or had long spines.

The authors suggest that this multiple-threshold system may be more prevalent than previously thought, and anticipate more examples coming to light.

QUESTIONS

Question 1

What are polyphenic regulatory developmental mechanisms?

Answer:

Question 2

Can you think of an example of polyphenic regulatory developmental mechanisms besides the beetles mentioned in this paper.

Answer:

Question 3

The authors use the “rock-paper-scissors” analogy to describe the potential result of this two threshold system when it comes to reproductive success in dung beetles. As in the game of rock-paper-scissors, each possible pair-wise comparison has a clearly defined winner. Give a hypothetical example of what this might look like in the context of dung beetle mating success.

Answer:

Question 4

What is the difference between the systems described in this paper and the other examples of male trimorphism cited by the authors (in isopods, lizards, and birds)?

Answer:

Question 5

Why might a trimorphic system such as this evolve? Why wouldn’t natural selection just drive all males to have the biggest possible horn, spine, or whatever the ornament involved is?

Answer:

What exactly was Hooker's response to Darwin's, Origin of Species? Thank you for your help. I need help deciphering what his opinions truly were.

Hooker, J. D. 1859. [Review of] On the origin of species. Gardeners' Chronicle (31 December): 1052. Part 1.

From the above expressions it will be inferred that we have risen from the perusal of Mr. DARWIN'S book much impressed with its importance, and have moreover found it to be so dependent on the phenomena of horticultural operations, for its facts and results, and so full of experiments that may be repeated and discussed by intelligent gardeners, and of ideas that may sooner fructify in their minds than in those of any other class of naturalists, that we shall be doing them (and we hope also science) a service by dwelling in some detail upon its contents. Thus much we may premise, that it is a book teeming with deep thoughts on numberless simple and complex phenomena of life; that its premises in almost all cases appear to be correct; that its reasoning is apparently close and sound, its style clear, and we need hardly add its subject and manner equally attractive and agreeable; it is also a perfectly ingenuous book, bold in expressions as in thought where the author adduces what he considers clear evidence in his favour, frank in the statement of objections to the hypotheses or conclusions founded on its facts and reasonings; and uniformly courteous to antagonistic doctrines. In fine, whatever may be thought of Mr. DARWIN'S ultimate conclusions, it cannot be denied that it would be difficult in the whole range of the literature of science to find a book so exclusively devoted to the development of theoretical inquiries, which at the same time is throughout so full of conscientious care, so fair in argument, and so considerate in tone. . . . Hitherto most [naturalists] have, as we have already observed, contented themselves with the hypothesis that they were independently created, and the minority have clung to the only other explanation hitherto conceived, that they have all been created by variation from a single first-created living organism, or a few such. Now it must be borne in mind that both these views are mere hypotheses in a scientific point of view; neither has any inherent or prescriptive right to a preference in the mind of the impartial inquirer; but the most superficial observation will show that the hypothesis of original creations is incapable of absolute proof, except the operation be witnessed by credible naturalists, and can only be supported by facts that are either not conclusive against the opposite doctrine, or may be regarded as equally favourable to it; and this hypothesis is hence placed at a disadvantage in comparison with that of the creation of species by variation, which takes its stand on the familiar fact that species do depart from the likeness of their progenitors, both in a wild and domestic state. On the other hand the hypothesis of creation by variation labours under the disadvantage of being founded upon a series of phenomena, the action of each of which individually, as explained by Mr. DARWIN, would appear to prevent the possibility of species retaining their characters for any length of time, and it therefore appears at first sight opposed to the undisputed fact, that many hundreds of animals and plants have transmitted their characters unchanged (or nearly so) through countless generations, and covered, even within the historic period, many square miles of country each with millions of its exact counterpart. To explain this anomaly and to raise this hypothesis of creations by variation to the rank of a scientific theory, is the object of Mr. DARWIN'S book, and to do this he has endeavoured to invent and prove such an intelligible rationale of the operation of variation, as will account for many species having been developed from a few in strict adaptation to existing conditions, and to show good cause how these apparently fleeting changelings may by the operation of natural laws be so far fixed as to reconcile both the naturalist and the common observer to the idea, that what in all his experience are immutable forms of life may have once worn another guise. The hypothesis itself is a very old one; it was, as all the world knows, strongly advocated by LAMARCK, and later still by the author of the "Vestiges of the Natural History of the Creation," but neither of these authors were able to suggest even a plausible method according to which Nature might have proceeded in producing suitable varieties, getting rid of intermediate forms, and giving a temporary stability to such as are recognised as species by all observers. Mr. DARWIN has been more successful, though whether completely so or not the future alone can show. We shall proceed to examine his method in another article.

1. What was Darwin's theory of pangenesis and how did it fit his model of blending inheritance? How did it allow for the influence of the environment on hereditary characters?

2. How was the idea of environmental influence criticized by Weismann? What his idea of "germ plasm"?

3. What were Mendel's laws on the segregation of traits and on recessive and dominant traits? How did he support these ideas with evidence?

4. What was Galton's argument regarding the inheritance of genius and how did he attempt to prove it?

1. What is the definition of eugenics? What is the difference between positive and negative eugenics?

2. What was "feeblemindedness"? Why did scientists want to eliminate these people from the population?

3. What was the argument presented for sterilization based on the Jukes family history?

4. How was feeblemindedness portrayed in the Norton pamphlet on “Selective Sterilization in Primer Form”?

5. How does the Carrie Buck case illustrate the concerns of eugenecists? How does it illustrate social values of the time?

1. What was the Kallikak family study, and how did it differ from the Jukes family study? What were its conclusions?

2. What were five factors that contributed to a growing concern over immigration and its threat to "nativism." (Be sure you know what American nativism was.)

3. What was the Immigration Restriction Act? How did passage of the act further eugenic goals?

4. How were eugenic doctrines popularized? What are some examples of positive eugenics?

5. What is the concept of "mental age" on which the Binet test was based? What did early researchers think they were measuring with these tests?

1. What were the results of the I.Q. test administered to World War I draftees? How did some people criticize this test and its results?

2. How did increasing research on development and genetics call into question the simple unit-character assumptions of earlier eugenecists?

3. What concerns did German “racial hygienists” express about different birthrates among Germans, Slavic peoples, and southern Europeans?

4. How was the rise of National Socialism (Nazism) in Germany based on promoting the genetically “healthy” and preventing reproduction among the “unhealthy”? Who was included in the unhealthy category?

5. What was the purpose of the German “health courts”? How did U.S. sterilization laws serve as models for German sterilization programs?

1. How were Margaret Sanger’s view on birth control similar to and different from eugenics?

2. What were the fears over the “population explosion” in the 1960s?

3.What similarities are there between the case of the Relf sisters and Madrigal vs. Quilligan?

4. How were sterilizations in the 1960s and 1970s similar to and different from the eugenic sterilizations of the 1920s and 1930s?

5. Why were so many women sterilized in Puerto Rico?

1. What are the basic particles of the atom? What is an isotope?

2. What were the contributions of Roentgen, Becquerel, and Marie Curie to the discovery of radioactivity?

3. How did Rutherford explain radioactive decay (Experiment 1)? How are atoms of one element transmuted into another element during radioactive decay?

4. What was Thompson’s model of the atom? What was Rutherford's model and how did he prove he was right (Experiment 2)?

5. What is the basic idea behind a nuclear chain reaction (fission)? Be able to explain 92235U → 56142Ba + 3691Kr + 3 neutrons + energy.

6. What were the circumstances that led Einstein to write to Roosevelt? What did he tell him?

1. How did the timing of the various decisions about deciding to make a bomb, making the bomb, and deciding to drop it coincide with the course of World War II? 2. What effect did the death of Roosevelt have on the decision to drop the bomb?

3. How did the relationship between the United States and the Soviet Union affect the decision to drop the bomb?

4. In what ways did Bohr, Szilard, and Franck try to get the politicians to think about the consequences of dropping the bomb? What were their various recommendations about international control?

5. How was the Interim Committee involved in the decision to drop the bomb? Which scientists advised the committee and what did they recommend?

1. How did Oppenheimer's attitudes toward the atomic bomb change over his lifetime? After the war was over, what was he advocating in relation to the bomb?

2. What were the reasons for and against initiating the project to build the atomic bomb? Did these reasons change during the course of the war?

3. What were the reasons in 1945 for and against dropping the bomb in a surprise attack?

4. With the benefit of hindsight, of more knowledge about the actual state of Japan in 1945, and of further understanding about the effects of the bomb, do you still think that the reasons you suggested in answer to question 3 are valid? Do you think there was any way to have done things differently?

1. How did the United States people first learn of the bombing of Hiroshima? What were they told?

2. What alternative to using the bomb was always mentioned by those justifying the bombings of Hiroshima and Nagasaki?

3. What was the Potsdam ultimatum and how did the Japanese respond? Why did they reject it?

4. What possibilities for a negotiated peace settlement with Japan existed during the summer of 1945? Why were they unsuccessful?

5. When and how did the American public first begin to learn about the effects of the bombings on the people of Hiroshima and Nagasaki?

1. What were some of the reactions of scientists to the bombing of Hiroshima and Nagasaki?

2. What were the major concerns of scientists after the war regarding the development and control of nuclear weapons?

3. How did the events of the Cold War influence the development of the Hydrogen Bomb?

4. What was the recommendation of the General Advisory Committee concerning the H-bomb, and on what reasons was it based?

1. In the years after World War II, how did scientists justify further research and development of nuclear weapons? How did cultural images facilitate this process? 2. What prompted U.S. policymakers to launch the "peaceful atom" campaign?

3. How was civil defense used to encourage public acquiescence during the early years of the nuclear arms race?

4. Why were so many civil defense campaigns directed toward women and children?

5. Did CDA materials provide an accurate portrayal of nuclear war?

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