Chapter 1: LEARNING ABOUT HUMAN BIOLOGY

1 LEARNING ABOUT human biology Chapter Outline THE CHARACTERISTICS OF LIFE OUR PLACE IN THE NATURAL WORLD Humans have evolved over time Humans are related to all other living things—and they have some distinctive characteristics life’s organization Nature is organized on many levels Organisms are connected through the flow of energy and cycling of materials USING SCIENCE TO LEARN about the natural world Science is a systematic study of nature Many scientists conduct experiments Science never stops CRITICAL THINKING IN SCIENCE AND LIFE Evaluate the source of information Evaluate the content of information SCIENCE IN PERSPECTIVE It is important to understand what the word theory means in science Science has limits LIVING IN A WORLD OF INFECTIOUS DISEASE Emerging diseases present new challenges Antibiotics are a major weapon against infectious disease Increasing resistance to antibiotics is a major public health issue CONNECTIONS: HOMEOSTASIS SUMMARY Review questions critical thinking EXPLORE ON YOUR OWN your future Objectives List features that distinguish living organisms from nonliving matter. Explain the interrelatedness that exits among organisms. Describe the general pattern of energy flow through Earth’s life forms, and explain how Earth’s resources are used again and again (cycled). Explain the interdependency that exists among organisms. List the steps of the scientific method of inquiry and use an example to illustrate. Define the word “theory” as correctly used in science. Understand, as well as you can, what limitations are imposed on science and scientists. Explain the importance of alternative hypotheses and control groups in scientific experimentation. Recognize the cause of infectious disease and the role of antibiotics in their treatment. Key Terms cell homeostasis primates vertebrates biosphere scientific method hypothesis experiment variable control group sampling error critical thinking fact opinion scientific theory emerging diseases antibiotic Lecture Outline Current world events seem chaotic. Infectious diseases such as “bird flu” pose global threats. Natural disasters cause widespread devastation. Human activities greatly affect our environment. Despite the chaos, we have tools available to help us meet these challenges. Systematic observation allows us to ask questions and find answers. Scientific investigation helps us to understand our place in the world. 1.1 The Characteristics of Life Several basic characteristics allow us to distinguish between living things and nonliving objects. Living things, though, have many distinctive features: Living things take in and use energy and materials. Living things sense and respond to changes in their environment. Living things consist of one or more cells. Living things maintain homeostasis. Living things reproduce and grow. Our Place in the Natural World Humans have evolved over time. Human beings are a part of biological “evolution”—the change in organisms through the generations. Humans are mammals belonging to the animal kingdom, one of the four kingdoms of life in the domain Eukarya. Humans are related to all other living things—and they have some distinctive features. Humans share characteristics with our closest primate relatives. Humans also have distinctive features: increased dexterity, large brain, analytical skills, sophisticated communication, and culture. Life’s Organization Nature is organized on many levels. Atoms and molecules are nonliving materials from which all of nature is built. Cells are organized into increasingly complex levels: tissues >>> organs >>> organ systems >>> organisms. Organisms, in turn, form populations >>> communities >>> ecosystems >>> biosphere. Organisms are connected through the flow of energy and the cycling of materials. Energy flows from the sun. Plants (“producers”) trap this energy by photosynthesis. Animals (“consumers”) feed on the stored energy in plants, using cellular respiration. Bacteria and fungi (“decomposers”) break down the biological molecules of other organisms in order to recycle raw materials. All organisms are part of networks that depend on one another for energy and raw materials. Using Science to Learn About the Natural World Science is a systematic study of nature. Biology, like all science, pursues a methodical search for information that reveals the secrets of the natural world. Explanations are sought using an approach known as the “scientific method”: Observe some aspect of nature. Ask a question about the observation or identify a problem to explore. Develop a hypothesis. Make a prediction. Test the prediction. Repeat the tests or develop new ones. Analyze and report the tests and conclusions. Many scientists conduct experiments. Experiments involve tests in which conditions are carefully controlled. Control groups are used to identify side effects during a test that involves an experimental group. The experimental group experiences all of the same conditions as the control except for the variable being studied. The sample size must be large enough to be representative of the whole, that is, to avoid sampling error. Science never stops. Single experiments rarely provide concrete answers. Conclusions must be adapted to reflect all findings. Critical Thinking in Science and Life Critical thinking is an objective evaluation of information. Evaluate the source of the information. Let credible scientific evidence, not opinions or hearsay, do the convincing. Question credentials and motives. Evaluate the content of the information. Be able to distinguish between cause and correlation. Separate facts from opinions. Science in Perspective It is important to understand what the word theory means in science. A scientific theory is a related set of hypotheses that form a broad-ranging explanation of many phenomena. Theories are accepted or rejected on the basis of tests and are subject to revision. Scientists must be content with relative certainty, which becomes stronger as more repetitions are made. Scientists must be prepared to change their minds in light of new evidence. Science has limits. Science is limited to questions that can be tested; subjective questions do not readily lend themselves to scientific analysis or experiments. Science has the potential to be used for controversial endeavors, which means that all of society must commit to responsible use of scientific knowledge. Living in a World of Infectious Disease Emerging diseases present new challenges. These diseases have either recently appeared or become widespread. High population density and global travel have made them more common. Antibiotics are a major weapon against infectious disease. Antibiotics are natural chemicals that can destroy bacteria. Antibiotics will not work against viruses. Increasing resistance to antibiotics is a major public health issue. Abuse of antibiotics has lead to an increased number of antibiotic-resistant bacteria—this is becoming a major health concern. 1.8 Connections: Homeostasis A. All organ systems contribute to homeostasis. Suggestions for Presenting the Material Although this chapter is a general introduction to human biology and to this textbook, it will be viewed very differently by instructor and student. For the instructor, this chapter is a review rather than a preview. That means the instructor must take extra care not to “intimidate” the students during early lectures. The following points will help the instructor to introduce the material. A casual glance at the chapter contents will reveal terms unfamiliar to most students. These might include: metabolism, homeostasis, and DNA. Individual instructors will have to decide if these terms need explanation now or are to be deferred until later. Possibly this decision will depend on the time available. It is would be very easy to lose the attention and enthusiasm of newly enrolled students if too much is presented too soon so pacing is important. Figure 1.5 (levels of organization) is an excellent road map and can be used throughout the course to guide the progression along the organizational ladder. It can also be used in the exercise listed first in the “Classroom and Laboratory Enrichment” section below. The diagram in Figure 1.6 (flow of energy and cycling of materials) also has relevance to future lectures. When introducing it, stress the flow of energy and the recycling of raw materials. Sometimes students think that the methods of scientific investigation are used only by scientists. Show that this is not true by discussing the use of these methods in a routine investigation of “Why won’t the car start?” (See the “Classroom and Laboratory Enrichment” section below.) Explain carefully the necessity for control groups in scientific investigations. Point out the difficulty of determining which groups of human patients will not receive a valuable drug (the controls) and who will receive a possibly life-saving medication. Classroom and Laboratory Enrichment Bring several organisms into the classroom or lab. Ask your students to name characteristics that identify each item as living or nonliving. (For some organisms, this may be difficult to do without specialized equipment, such as a microscope.) Ask the students to identify equipment or experiments that would help to determine if an item is a living organism. Obtain an overhead transparency or use a PowerPoint slide of the levels of organization in nature (Figure 1.5). With the lower labels of the figure covered, ask your students to help you name each level as you proceed from left to right. Show the video Introduction to Biodiversity from the Suggested Videos below as a general introduction to biological diversity. Present fossil evidence (actual specimens or video) showing how a group of related organisms or a single genus (for example, Equus) has evolved and changed through time. Briefly list the steps of the scientific method in the wrong order. Ask the class to place them, one by one, in the correct order. Show how we use the scientific method in everyday problem solving, as illustrated by this example: Event Method Step a. Auto will not start………………………………….. a. Observation b. Battery dead………………………………………… b. Hypothesis Ignition problem…………………………………… Hypothesis Out of gas…………………………………………… Hypothesis c. Turn on headlights………………………………… c. Experiment Check spark at plug……………………………….. Experiment Check gas gauge…………………………………… Experiment Dip long stick into gas tank………………………. Experiment d. Headlights burn brightly (battery OK)…………… d. Analyze results Strong ignition spark……………………………… Analyze results Gauge says half tank, but no gas on stick………... Analyze results e. Gas gauge is not accurate; car needs gas to run… e. Generalize; form principle Classroom Discussion Ideas Of what possible value could infectious diseases be to the overall continuity of life on Earth? Could you propose one overarching reason for the deterioration of the quality of the Earth’s air, water, soil, etc.? During your first lecture, ask students to name as many characteristics of living things as possible. While this may at first seem like an obvious and overly simple exercise, students will be surprised at some of the less obvious characteristics, such as homeostasis. Ask your students to consider fire using the characteristics of living things. What is metabolism? What metabolic steps in humans are different from those found in green plants? What metabolic steps in humans are the same as those found in green plants? What are some examples of homeostasis? Why must living organisms be able to perform it? Provide a handout with pictures of 10 random organisms (or, better yet, let your students do this). Identify ways in which all of the organisms are similar, then ways in which all of the organisms are different. How would you classify (that is, place into meaningful groups) these organisms? Why is it important for a species to be able to change? Would a species be more successful if it could be assured of remaining the same from one generation to the next? Name some organisms you might find in a grassy area nearby. Using arrows, arrange the organisms in a diagram depicting energy flow and the cycling of materials (for help, see Figure 1.6). What are some organisms that may be invisible to the eye but are essential for the recycling of nutrients during decomposition? An animal carcass infested with insect larvae is not an attractive sight. Yet it is a biological necessity. Explore the role of these and other “recyclers.” Is there such a concept as the “balance of nature”? Humans are able to manipulate certain aspects of nature for their own benefit. However, it is often said that “humans are the only animals that engineer their own destruction.” Give examples to support this allegation. Distinguish among independent, dependent, and controlled variables. Can you identify each if presented with an actual experimental design? Why is it difficult to obtain a control group when selecting volunteers to test a new anticancer drug? How in general is research on humans different from research on animals? Is there a need for both types of research in science? Why is the term “scientific creationism” an oxymoron? Describe why this body of thought cannot be considered a science. How is a principle different from a belief? Those who wish to berate certain scientific principles sometimes say: “It’s only a theory.” This statement is used by creationists when referring to evolution. Does the use of “theory” in biology mean the concept is in doubt? Explain using examples. Term Paper Topics, Library Activities, and Special Projects Discover more about how the first cells are thought to have evolved. How do biologists “draw the line” between that which is living and that which is nonliving? Outline ways in which biologists attempted to explain inheritance of particular characteristics prior to the discovery of the role of DNA in heredity. Describe how any one of several modern scientific investigative tools (such as electron microscopy, radioactive labeling, gas chromatography, or gel electrophoresis) has made it possible to discover similarities and differences among living organisms. The supply of easily obtainable energy sources such as coal and oil is a matter of debate today. Some persons see a bleak future; others are optimistic. What are the issues that each of these camps sees? The pupal stage of insect metamorphosis is erroneously called the “resting stage.” Actually, there is a complete transformation of larval tissues to adult tissues. Consult several entomology and biochemistry texts to learn the current status of our knowledge concerning these transformations. The origin of life on this planet has always fascinated humankind. Several explanations have been advanced. Compare and contrast the principal ones that are still in contention today. Can we see evolution actually happening? Find examples of natural occurrences in the wild or experimental situations in the laboratory in which we can observe evolution occurring. Describe how Darwin’s development of his principle of evolution was an example of the scientific method in action. Selected Videos, Animations, and Websites VIDEOS TED Talk – Drew Berry Visualizing biology through computer animations. http://www.ted.com/talks/drew_berry_animations_of_unseeable_biology.html Science Friday – Why Don’t Spiders Stick to the Web? An applied example of the scientific method at work. http://www.sciencefriday.com/videos/bytopic/c100100/ Introduction to Biodiversity – Howard Rosen Productions A 15 minute film featuring E.O. Wilson explaining the concept of biological diversity and its importance to humans. http://www.bullfrogfilms.com/catalog/nat1.html Human Body – 101 A 3 minute National Geographic film on an overview of the human body. http://video.nationalgeographic.com/video/science/health-human-body-sci/human-body/human-body-sci/ ANIMATIONS The Scientific Method This Flash animation walks students through a tutorial and a virtual experiment to guide them through the scientific method. http://www.gccaz.edu/biology/glacier/scientific_method/index.swf WEBSITES Scientific Method An overview of the scientific method http://www.cod.edu/people/faculty/fancher/scimeth.htm Field Guide to Critical Thinking James Lett’s overview of Critical Thinking http://www.csicop.org/si/show/field_guide_to_critical_thinking/ Possible Responses to Review Questions As a living, human organism, I exhibit all of the characteristics of life: I take in energy and materials (food); respond to changes in my environment; grow from child to adult and have my own children; consist of many, many cells; and my body, with my help, seeks to maintain homeostasis for proper functioning. Homeostasis is important for a couple of reasons. First, it helps to explain how the body functions, including how cells, tissues, organs, etc. work together. Second, by understanding how the body is supposed to be balanced, we are better able to see what disrupts this balance and how to remedy it. Biological evolution, in its simplest statement, means change over time. At the basic, instructional level of our cells (DNA), changes occur that ultimately get “seen” by nature and “judged” as worthy (or not) of being passed on. For organisms that reproduce very quickly (such as a bacterium), these changes occur more frequently and are seen by us more quickly. For humans, who reproduce much more slowly, change is seen only over long periods of time. In looking at Figure 1.5, it is easy to see that life is layered, and that even complex entities, such as a human being, can be broken down into smaller, understandable pieces. The diagram also shows how all things are related; we cannot distance ourselves either from the cells that compose our tissues or from the environment in which we make our homes. A. A “hypothesis” is a single guess about why something is the way it is, and it is very limited in scope; a “theory,” on the other hand, is based on the compilation of many hypotheses all relating to the same phenomenon. Theories are more complete than hypotheses, but even they can change. B. the experimental group is the one in which the variables are manipulated, and the control group is the one in which nothing is allowed to change (a baseline). Possible Responses to Critical Thinking Questions 1. All life forms share the same basic hereditary material—DNA—the only difference being the sequence in which the code of the DNA is arranged. Just as the tiles in the question can be put together to create different pictures, so too can sequences of DNA be put together to create different animals; the letters of the DNA code thus act much like letters of the alphabet. Arranged one way, and letters of the alphabet can spell the word “goat”; arranged another, and you have the word “toga.” Both words are formed from the exact same letters, but the words mean very different things. 2. Stress, perception, distance, lighting—all of these factors and more can help to explain how even the most reliable of witnesses ends up presenting a version of the truth that may not be quite accurate. “Honest” errors, however, are not the only worry in the courtroom. Objectivity may not always be easy to maintain in the face of pressure from attorneys, family, or friends. The length of time between witnessing the crime and appearing in court both prompts forgetfulness and the retelling of events in one’s mind, such that the truth can become distorted. Some details of the crime are in fact subjective—intent is often hard to pinpoint and yet greatly colors the perceived severity of the crime. A surveillance camera can’t forget and is hard to fool, but humans are fallible, even when we try to be perfect. 3. For this experiment on hypertension you will need a group of human subjects who do not suffer from hypertension and who also have no history of it in their family (Group A). Secondly, you will need a population with a family history of hypertension (Group B). For experiment #1: have Group A consume a diet that is considered (from prior studies) to be high in salt content. Monitor any increases in hypertension. Compare these results to the hypertension development (if any) in Group B (diet has normal salt content but participants have family history). We would expect Group A to develop hypertension. We would also expect hypertension in those persons with a family history of it. For experiment #2: treat Group A as before, but increase the salt intake of persons in Group B. We would expect the blood pressures of those in Group B to climb even higher. Additional experiments could reverse the above by reducing the salt intake in both groups to see if hypertension is lowered. 4. Diets and especially dietary supplements already carry disclaimers that say the product has not been tested for efficacy and is not intended to diagnose, treat, or cure any particular condition. This is in small print and is necessary because the product has not undergone rigorous FDA testing. The glaring omission is the comparison of advertised results with the product (or device) and the data from a control group without the product. 5. Prayer as therapy on its own might elicit criticism from the scientific community simply due to its intangibility, but more and more evidence points to patient psychology as being important to eventual outcome. Careful experimental design therefore becomes essential, and in this case several questions can be raised as to the validity of the design, all of which would have elicited concern in the scientific community. Were all of the patients experiencing similar disease symptoms or were some patients in a more severe state than others? Was there a control group who was not prayed for, and what was the disease state of these patients? Were the patients themselves religious? Did Dr. Byrd and his colleagues directly decide which patients were being prayed for or did someone else make the assignments to eliminate selection bias during the study? How exactly were outcomes assessed? All of these questions, if not adequately addressed, would cause the study itself—not the subject—to be criticized. 1 Chapter One Learning About Human Biology 1 1 Chapter One Learning About Human Biology 1 2 Chapter One Learning About Human Biology 1 4 Chapter One Learning About Human Biology 1 4 Chapter One Learning About Human Biology 1