Foundations In Microbiology 1 1Th Edition By Kathleen Park Talaro – Test Bank Sample Test Answers to Writing to Learn Questions/Writing Challenge Questions CHAPTER 1 1. What does it mean to say microbes are ubiquitous? From the Latin ubique , meaning “everywhere”, it is a succinct way of saying that microbes exist everywhere throughout the natural world, even areas with extreme conditions. Other ways to express this idea are the terms universally widespread and constantly present. The only environments that are microbefree have probably been artificially sterilized by humans. 2. What is meant by diversity? The term diversity is used to denote the immense variety in different typ es of organisms, with regard to such characteristics as appearance, life style, and distribution. Although about 1.2 million different species of organisms have been discovered and named, this is only a small fraction of the true diversity present over the entire planet and its millions of habitats. The case study emphasizes that we are still at the early stages in exploring the richness of life (especially of the microbial type) that is hidden and largely unknown because of small size and inaccessiblity. 3. Most important events and discoveries: Many hundreds of separate scientists and labs contributed to the rise of microbiology during its early history. Tools such as the microscope allowed direct observation of samples and their microbial contents. Micro bes were subsequently seen as discrete entities that could be observed, described, and documented much like larger organisms. Development of laboratory techniques for culturing microbes using sterile techniques allowed macroscopic handling and control of microbes so they could be studied and understood in greater depth. Application of the scientific method and experiments to standardize the requirements for fact -based inquiries were very important. The abandonment of the spontaneous generation theory was e specially significant because it departed from superstition and prejudice in favor of the scientific method. The institution of the germ theory of disease and the development of aseptic techniques were an essential contribution to medical aspects of microb iology. The knowledge that microbes cause food spoilage and disease led to early attempts to control microbes using heat and other methods. 4. Use of the scientific method: A hypothesis is a statement put forth by an investigator that purports to explain a phenomenon based upon a collection of observations, tests, and other objective criteria. It can be tested experimentally. A theory is a statement of confidence that scientifically -based observations provide a factual explanation for some natural phenomenon . It is supported by measurable data collected from numerous experiments used to test the hypothesis. Examples: For years, it was not really known what was the exact cause of tooth decay. Various hypotheses were proposed that acid, sugar, tooth hygiene, and other factors were involved. Finally, after having the correct conditions for experimentation (on animals that lacked normal resident microbes), it was determined that a combination of excess dietary sugar, lack of cleaning, and certain streptococci living in the mouth were the primary factors. Likewise, the germ theory of disease started out as a hypothesis, but after thorough verification, it became not only a theory, but is now considered a law because it has held true over several centuries of inv estigation. 5. Classification of microbes Evolution is a process by which organisms gradually change (evolve) over long periods of time through inheritance of modified characteristics from ancestors. It asserts that all organisms arise from preexisting forms and that this relatedness shows itself by similarities in structure, physiology, and genetics. Biologists and microbiologists use various means to show the pattern of evolution, including trees, taxonomy, classification, and nomenclature. Taxonomy i s a hierarchical system, from general to specific, for assembling organisms into a scheme that emphasizes their origins and relatedness. Classification is the process of collecting organisms into distinct taxonomic groups according to defined characteristi cs. Nomenclature is the naming of these categories in collaboration with their level of classification. Most classification schemes are based on evolutionary relatedness, with organisms that are more closely related placed in the same taxonomic groups. The correct order of taxa, from broadest and most inclusive to most specific, is: Domain, Kingdom, Phylum, Class, Order, Family, Genus, and Species. The five Kingdom system groups the archaea with the bacteria in the prokaryotic category. In comparison th e domain system emphasizes the evolutionary separation of the Archaea from the Bacteria and their early relatedness with the Eukarya. The binomial system of nomenclature assigns a genus and species (scientific) name to each organism; the first letter of th e genus is capitalized, the species is lowercase, and the two names are underlined or italicized. This system standardizes naming and ensures consistency and universality. Names may also provide an indication of noteworthy characteristics of the organism s or its discoverer. 6. Sources for new infections (a) A large number of new infectious diseases arise from animals living in environments where they have crossed paths with humans. Since 1969, at least 20 new viral diseases have been reported in humans (see Making Connections 25.1). Most of these have not spread uncontrollably through the population, but a few, such as HIV and Zika virus infections, developed into pandemics. Some of the new diseases are caused by well -known microbes that have become dru g resistant (MRSA) and others have mutated to become more infectious for human beings (some influenza strains). (b) Most of the time outbreaks of newer diseases receive more negative attention from the media than is warranted, often leading to unfounded fear o f diseases and germ phobia rather than helping to educate and inform the public. Understanding the facts about disease outbreaks and learning methods of dealing with them would be a much more valuable contribution to sensible coverage. Chapter 2 1. Explain why all compounds are molecules but not visa versa. A molecule is any combination of two or more bonded atoms, regardless of the types of atoms present. Compounds are molecules that contain at least two different atoms. For example, O 2 and N 2 are molecules but not compounds, whereas CO 2 and NaCl are both molecules and compounds. 2. What causes bonding? Atoms form chemical bonds because they have a structure that allows them to lose, gain, or share the electrons in their outer orbitals. Covale nt bonds form when atoms share electrons. Elements that tend to make covalent bonds have valences that are more suitable for sharing electrons rather than donating or receiving. Ionic bonds form when an atom donates electrons to another atom, which leaves the participating atoms now oppositely charged. Atoms with unfilled outer electrons shells can easily lose or gain electrons to create stability and usually form ionic bonds. Hydrogen bonds from between atoms that have polar covalent bonds that are shared unequally. This creates partial charges on atoms within molecules and creates attraction between oppositely charged atoms on the same or adjacent molecules. 3. Why are some covalent molecules polar and others nonpolar? Polarity of covalent molecules arises w hen the electron pairs of atoms in the molecule are being shared unequally. This is usually because the atoms differ greatly in the sizes of their atomic nuclei and number of protons. The atom exerting greater electronegativity (pull on the electrons) ke eps the electrons in its sphere. Examples of molecules that show polarity are H 20 and phospholipids. Since water is a polar molecule, it allows intramolecular hydrogen bonding, which makes water cohesive. 4. What causes diatomic molecules? A few elements exist in their natural elemental state as two identical atoms bonded by a covalent bond. Examples include oxygen (O 2), hydrogen (H 2), and chlorine (Cl 2). This state arises from the electron numbers in their outer orbitals. Diatomic elements are most sta ble when they share these electrons with a partner having the same number of electrons. Chlorine, for example, has a single unpaired electron that
