Answers to Mastering Concepts Questions

1.1
1. What characteristics distinguish the living from the nonliving?

All organisms (living individuals) are organized; use energy; maintain a constant internal environment; reproduce, grow and develop; and evolve.

2. List the levels of life’s organizational hierarchy from smallest to largest, starting with atoms and ending with the biosphere.

Atom, molecule, organelle, cell, tissue, organ, organ system, organism, population, community, ecosystem, biosphere

3. What are the roles of natural selection and mutations in evolution?

Individuals that are best adapted to their environment are most likely to reproduce. Offspring of these well-adapted individuals will likely have the same favorable traits as their parents. As this process continues, generation after generation, the genetic makeup of the population changes, or evolves. Mutations generate the genetic variation on which natural selection acts.

1.2
1. What are the goals of taxonomy?

The goals of taxonomy are to provide a unique name for species, and then classify each species based on evolutionary relationships.

2. How are domains related to kingdoms?

Domains are larger, more encompassing taxonomic categories than kingdoms. Each domain may contain one or several kingdoms.

3. Which kingdoms contain eukaryotic organisms?

Eukaryotes are organisms whose cells contain a nucleus.  The three most familiar groups of eukaryotes are Kingdom Fungi (which contains all of the fungi), Kingdom Plantae (which contains all of the plants), and  Kingdom Animalia (which contains all of the animals).  A fourth group of eukaryotes are the protists, which include many groups of unrelated eukaryotes.

1.3
1. What are the components of scientific inquiry?

Scientific inquiry begins with making observations and asking questions based on prior knowledge.  The process continues by forming a hypothesis and making predictions about what is expected if the hypothesis is supported.  An experiment must be designed to test the hypothesis (often the experiments are designed with a control).  The experiment allows the scientist to collect data and then interpret the data and make conclusions in light of prior knowledge.  Finally, the results are provided to the scientific community for peer review.

2. Identify the elements of the experiment summarized in the Why We Care box on page 15.

Sample size = 100 rats per treatment. Independent variable = presence or absence of saccharin. Dependent variable = incidence of tumors. Standardized variable = brand of chow. Control = group with no saccharin added to chow.

3. What is the difference between a hypothesis and a theory?

Hypotheses are untested tentative explanations, whereas theories have a great deal of independent supporting evidence.  Theories are also much more comprehensive and often have been tested across multiple scientific disciplines.

4. What are some limitations of scientific inquiry?

Scientific inquiry cannot answer subjective questions related to beauty, morality, ethics, or religion. Sometimes, multiple interpretations can be made based on the same experimental evidence.  It is also possible for data to be misinterpreted. 

1.4
1. What observations led Darwin and Wallace to predict the existence of a long-tongued moth in Madagascar?

They both made observations of orchids with long nectar tubes and reasoned that there must be an organism that could reach the sweet nectar at the bottom of the nectar tube.  If the organism could reach the nectar, it would then pollinate the orchid.

2. How does this story illustrate discovery science?

Darwin and Wallace inferred the relationship between the moth and the orchid based on their observations.  Many years later, scientists found the moth when cataloging the insects of the region.  Not all discoveries in science come from a controlled experiment, but the discoveries still require close observation, prediction, and collaboration with other scientists.

Answers to Write It Out Questions

1. Describe each of the five characteristics of life, and list several nonliving things that possess at least two of these characteristics.

a) Organization –a hierarchical pattern from atoms to the biosphere; b) requires energy – metabolic reactions acquire and use energy; c) maintains internal constancy – even in a changing environment, conditions inside living organisms remain within a constant range; d) reproduction, growth and development – organisms make new organisms similar to themselves, and those organisms mature into adults; e) evolution – the genetic makeup of a population changes over time, often as it adapts to the environment through natural selection.  Examples of nonliving things: a house is structurally organized and maintains a relatively constant temperature; automobiles are organized, require energy, and “evolve” as manufacturers come out with new models; crystal formations are organized and grow; viruses are organized and evolve; fires use energy and grow.

2. Draw and explain the relationship between producers, consumers, and  decomposers.

Answers will be visual; see Fig. 1.4. Producers convert light energy and nutrients into a form that consumers can also use.  When organisms die, the decomposers release the nutrients back into the soil to be taken up by the plants.

3. What is homeostasis? Give an example other than those mentioned in the book.

Homeostasis is the maintenance of a constant internal environment. An example is the human body’s ability to conserve water by producing more concentrated urine when water is scarce.

4. Describe the main differences between asexual and sexual reproduction. Why are both types of reproduction common?

In asexual reproduction all the genetic information comes from one parent, so organisms are almost identical.  In sexual reproduction the genetic information comes from two parents, generating variation.  Asexual reproduction is most adaptive in habitats that are stable.  Sexual reproduction allows populations to adapt to changing environmental conditions.

5. Describe a specific adaptation in an organism familiar to you, and explain how the environment could have selected for that adaptation.

[Answers will vary]

6. How are the members of the three domains similar? How are they different?

The members of all three domains are made of at least one cell and contain DNA.  Domains Bacteria and Archaea contain prokaryotic organisms; whereas domain Eukarya contains eukaryotes (their cells contain a nucleus). Also, the eukaryotes can be single-celled or multicellular, whereas the prokaryotes are all single-celled. DNA sequences differentiate all three domains.   

7. Find an example of a news story that describes an experiment. Which components of the scientific method can you identify in the article?

[Answers will vary]

8. Give two examples of questions that cannot be answered using the scientific method. Explain your reason for choosing each example.

Science cannot answer questions regarding moral, ethical, aesthetic, and religious issues.  Two examples of questions that science cannot answer are “Is a rattlesnake or a peacock more beautiful?” and “Is it ethical to use animals in cosmetics research?”

9. If you dissect and label the parts of an earthworm, are you “doing science”? Why or why not? Give an example of a testable hypothesis that could result from dissecting organisms.

The act of dissecting and identifying the parts of an earthworm is observational, and it provides investigators with the anatomical knowledge needed to ask questions and develop hypotheses.  A testable hypothesis resulting from such an activity could address the relationship between the size of an earthworm and the number of segments.

10. Studies show that research funded by drug companies is more favorable to new drugs than is publicly funded research. How can scientists avoid such systematic biases?

Double-blind experiments and the freedom to publish all results, both positive and negative, would help scientists to achieve studies without bias. 

11. For each of the following examples, state whether each of the following faults occurred: (I) experimental evidence does not support conclusions; (II) inadequate controls; (III) biased sampling; (IV) inappropriate extrapolation from the experimental group to the general population; (V) sample size too small.
a) “I ran 4 miles every morning when I was pregnant with my first child,” the woman told her physician, “and Jamie weighed only half as much as a normal baby. This time, I didn’t exercise at all, and Jamie’s sister had normal birth weight. Therefore, running during pregnancy must cause low birth weight.”
b) Eating foods high in cholesterol was found to be dangerous for a large sample of individuals with hypercholesterolemia, a disorder of the heart and blood vessels. It was concluded from this study that all persons should limit dietary cholesterol intake.
c) Osteogenesis imperfecta (OI) is an inherited condition that causes easily fractured bones. In a clinical study, 30 children with OI were given a new drug for 3 years. The children all showed less fatigue, improved bone density, and a lowered incidence of fractures compared with before treatment began. The conclusion: the drug is effective in treating OI.
d) Researchers studied HIV in blood and semen from 11 HIV-infected men. In eight of the men, the virus was resistant to several medications. In two men, viruses from the blood were resistant to the class of drugs called protease inhibitors, but viruses from semen were not resistant. The researchers concluded that protease inhibitors do not reach the male reproductive organs.

Scenario a): the evidence supports the conclusion, but faults (II), (IV), and (V) mean that the evidence is unreliable.  Scenario b):  Without more information, it is not possible to determine whether fault (II) occurred; fault (IV) is the main problem.  Scenario c):  The main faults are (II) and (V).  Scenario d):  Fault (V) certainly occurred; faults (I) and (IV) are possible; without more information, it is not possible to determine whether faults (II) or (III) occurred.

12. Design an experiment to test the following hypothesis: “Eating chocolate causes zits.” Include sample size, independent variable, dependent variable, the most important variables to standardize, and an experimental control.

Overall, the experiment would require dividing a pimple-free population into two groups, one of which received chocolate and the other not receiving chocolate.  After some predetermined amount of time, the researchers would measure the density of pimples in each group.  The independent variable in this experiment is the treatment group (chocolate or no chocolate), and the dependent variable is the density of zits.  The experiment should include a large sample size (hundreds of people at minimum).  The variables to standardize include other components of the diet, the age group of the subjects, and the subjects’ history of skin problems.  The control group would consist of individuals not consuming chocolate.  

13. Morgellons syndrome is a medical mystery. Patients experience sensations of stinging, biting, or crawling skin; they may also have rashes or sores that are slow to heal. Scientists have proposed several hypotheses to explain the symptoms: the patients may be imagining the disorder and creating the sores by picking at their skin; “Morgellons syndrome” may simply be a new name for a recognized skin disorder such as dermatitis or a bacterial infection; or exposure to toxins in the environment may cause the symptoms. If you had unlimited resources, what data might you collect to test each hypothesis?

Some possible data to collect could include the following:  Hypothesis 1 – video observations or 24 hour surveillance to check for picking sores; Hypothesis 2 – collect samples from all infected individuals and test for the presence of bacteria; Hypothesis 3 – test the home and work environments of all patients for toxin levels.

14. Review “The Saccharin Scare” box on page 15. If you were investigating a possible saccharin-cancer link today, how would you improve on the design of the experiments conducted in the 1970s? Also, develop a hypothesis that could explain why more male than female rats developed tumors. Design an experiment that would help you test your hypothesis.

Improvements could include multiple treatment levels for saccharin dosage, larger sample sizes in each treatment group, and multiple treatments over several animal species, all while maintaining a consistent experimental design.  Potential hypotheses and experimental design will vary, but experiments should have a large sample size for the control and experimental groups, state specific standardized variables, include a measurable outcome, and have a manipulated variable that differs between the groups.

Answers to Pull It Together Questions

1. What are the elements of a controlled experiment?

A controlled experiment consists of a control group and experimental group.  There should only be one difference between the two groups: the variable being tested in the experiment.  The variable being tested is the independent variable, and the variable being measured is the dependent variable (because it may depend on the effects or presence of the independent variable).  The control group is one that is not receiving or exposed to variable being tested.  The control group could be a healthy population compared to a diseased population or a population receiving no treatments compared to a population receiving treatments.  Standardized variables are held constant for both groups (the control group and the experimental group):  the same age of participants in a drug study, or the same soil type in a plant growth study for example.

2. What is the relationship between natural selection and evolution?

Natural selection is the driving force for evolution.  Populations have variation in traits that are passed on from parents to offspring.  The variation among individuals in populations means that some individuals in the population will be better able to survive environmental stress, more able to find resources, more able to avoid predation, and ultimately, more likely to reproduce.  Those individuals which successfully reproduce will pass their more adaptive traits on to their offspring.  

3. List the levels of biological organization, from atoms to the biosphere, and describe the relationships among them.

Atoms-Molecules-Organelles-Cells-Tissues-Organs-Organ Systems-Organism-Population-Community-Ecosystem-Biosphere.

Atoms (like an atom of hydrogen or oxygen) are the smallest particles which can be combined and assembled into molecules like water (H2O).  Molecules can then be assembled into organelles and cells.  Cells are the smallest unit of organization that can be considered living and are the “building blocks” of organisms.  Most multicellular organisms combine groups of cells into functional units called tissues.  Different tissue types can be combined in an organ.  Multiple organs combine to provide the function of an organ system. Organisms of the same type live together in populations.  Many different populations that live together make up a community.  The non-living components of the environment that interact with individuals of a community compose an ecosystem.   All the ecosystems on the planet make up the biosphere.

4. Where do the protists and kingdoms Plantae, Animalia, and Fungi fit into this concept map?

All four groups belong to the Domain Eukarya since they have a nucleus.  The protists include single-celled and multicelled individuals that are classified into several kingdoms. They may be heterotrophic and autotrophic.   The Kingdom Fungi are mostly multicellular (though there are a few unicellular forms) and are heterotrophic.  The Kingdom Plantae consists of all multicellular forms, and they are all autotrophic.  The Kingdom Animalia is also all multicellular forms, but they are all heterotrophic.