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Discover Biology SIXTH EDITION CHAPTER 1 The Nature of Science and the Characteristics of Life 2015 W. W. Norton & Company, Inc. Anu Singh-Cundy Gary Shin Slide 2 CHAPTER 1 The Nature of Science and the Characteristics of Life 2015 W. W. Norton & Company, Inc. EARTHBOUND EXTRATERRESTRIAL? OR JUST ANOTHER MICROBE IN THE MUD? 1.1 The Nature of Science People like you are contributing to the advance of science Science is a body of knowledge and a process for generating that knowledge Scientific hypotheses must be testable The scientific method requires objectivity 1.2 The Process of Science Observations are the wellspring of science Scientific hypotheses make clear-cut predictions Scientific hypotheses must be refutable, but cannot be proved beyond all doubt Hypotheses can be tested with observational studies Correlation is not causation Experiments are the gold standard for establishing causation Slide 3 1.3 Scientific Facts and Theories 1.4 The Characteristics of Living Organisms Living organisms are composed of cells Living organisms reproduce themselves via DNA Living organisms obtain energy from their environment Living organisms sense their environment and respond to it Living organisms actively maintain their internal conditions Groups of living organisms can evolve 1.5 Biological Evolution and the Unity and Diversity of Life Populations of a given species can evolve over the generations Natural selection favors individuals with adaptive traits Natural selection adapts a population to its habitat Darwin and Wallace explained how natural selection produces new species We can categorize all known species into three domains of life 1.6 The Biological Hierarchy BIOLOGY MATTERS: SCIENCE AND THE CITIZEN APPLYING WHAT WE LEARNED: RESEARCHERS WRANGLE OVER BACTERIA 2015 W. W. Norton & Company, Inc. Slide 4 Earthbound Extraterrestrial? Or Just Another Microbe in the Mud? The claim: Mono Lake bacterium has arsenic instead of phosphorus in its DNA! Are you convinced? How does science settle such controversies? We will return to this story! Slide 5 Biology Is the Scientific Study of Life This course is about us and how we connect with other living beings and our surroundings. Many controversies facing society today require an understanding of the underlying science, so we can make informed decisions. Is de-extinction a good idea? Slide 6 The Nature of Science The spirit of inquiry is the driving force behind science. Scientific thinking is objective and values evidence over all other ways of discovering the truth. Do you recall any questions about nature that you asked when you were little? Slide 7 Citizen Scientists Are Contributing to the Growth of Scientific Knowledge Data collected by birders shows migratory birds arent going as far south in the winter as they used to. Slide 8 Some Examples of Citizen Science Projects Slide 9 Science Is a Body of Knowledge and a Process for Generating That Knowledge Slide 10 The scientific method represents the core logic of how science works. The scientific method is also known as the process of science. It is central to scientific inquiry, and is also applied in other areas such as sociology and law. The Process That Generates Scientific Knowledge Is Called the Scientific Method Slide 11 The Scientific Method: A Concept Map The scientific method relies on observations, hypotheses, and hypothesis testing through additional observations and/or experiments. Slide 12 The Scientific Method Requires Objectivity Independent researchers should be able verify the observations and experimental results. The process of peer review seeks to limit bias and fraud in the scientific community. Peer review is assessment by experts who have no direct involvement in the research under review. Slide 13 A Deeper Look at the Scientific Method Slide 14 Observations Are the Wellspring of Science The process of science begins with observations of the natural world. An observation is a description, measurement, or record of any object or phenomenon. An observation must be reproducible. Slide 15 A Hypothesis Is an Educated Guess That Seeks to Explain the Observations Slide 16 Scientific Hypotheses Must Be Testable and Refutable Slide 17 A Scientific Hypothesis Leads to Testable Predictions Slide 18 Hypotheses Can Be Tested with Observations or Experiments or Both Observational studies can be descriptive (listing what, where, when, how much) or analytical (asking why; seeking to explain patterns in nature). Descriptive and analytical studies report information (data) that can be used to build and then test a hypothesis. Scientists use mathematical tools such as statistics to estimate the reliability of data. Slide 19 An Observational Study: Higher Fish Consumption Is Correlated with Lower Risk of Death from Heart Disease A variable is any aspect of nature that is capable of changing. Correlation means two variables behave in an interrelated manner: the value of one variable predicts the value of the other variable. Slide 20 Correlation Is Not Causation Observational studies cannot demonstrate that a change in one variable is the cause of a change in the other variable. The correlation between fish consumption and better heart health could be a spurious correlation. In a spurious correlation, a third variable, such as higher income, is the real cause of the observed correlation. Is global warming driving young people to college? Temperature ( 0 C) Source: Department of Labor Statistics Percent high school grads entering college There is a correlation between global warming and college enrollments! Slide 21 Experiments Are the Gold Standard for Establishing Causality An experiment is a repeatable manipulation of one or more aspects of the natural world by the investigator. In a controlled experiment, at least two groups are compared, with the treatment group experiencing a change in one variable, whereas that variable is constant for the control group. Control Treatment Heart disease mortality Slide 22 A Controlled Experiment to Test the Health Benefits of Fish Oil Supplements Study subjects: 2,000 men diagnosed with heart disease, randomly assigned to control or treatment group Control group: not directed to alter diet in any way Treatment (experimental) group: asked to take 900 mg of fish oil daily Conclusion: The experimental data support the hypothesis Heart disease mortality Slide 23 In an Experiment, the Independent Variable Is Manipulated in the Treatment Group The variable that the investigator manipulates in an experiment is called the independent variable. Typically, there is only one independent variable in an experiment, and all other variables are kept constant as much as possible. The independent variable is altered only for the treatment group (not for the control group). The dependent variable is a variable that can potentially change when the independent variable is altered. The goal in an experiment is to measure how a change in the independent variable changes the value of the dependent variable; the dependent variable is not expected to change in the control group. Slide 24 A Double-Blind Study Reduces Experimenter Bias and Estimates the Placebo Effect in Studies on Humans In a double-blind study, neither the subjects nor the investigator knows who is receiving the treatment and who is a control subject. The placebo effect is the (potentially false) feeling in a study participant that he or she has benefited from the experimental treatment. Dependent variable This is the effect. Independent variable This is the cause. Slide 25 Testing Does Not Prove a Hypothesis with Absolute Certainty A hypothesis can be supported, but never proven true. When a hypothesis is refuted, it must be reexamined and then changed or discarded. A single black swan can refute the hypothesis that all swans are white. Slide 26 A Scientific Theory Is a Major Body of Knowledge That Has Stood the Test of Time Scientific hypotheses becomes a scientific theory: After they have been repeatedly confirmed through diverse methods of testing When they are accepted by experts as the best explanation of the truth about the phenomenon Slide 27 A Scientific Fact Is a Direct and Repeatable Observation about the Natural World Examples of Scientific TheoriesExamples of Scientific Facts Germ theory of disease: some diseases are caused by infectious microbes. The HIV-AIDS virus contains genetic material. Cell theory: all living organisms are composed of one or more cells. Many different types of cells can be found in the body of an adult human. Evolution by natural selection: natural variables may favor individuals with certain inherited traits over individuals that lack those traits, and as a result the favored traits become more common in the succeeding generations. A population of E. coli bacteria can evolve over time. Anthropogenic climate change theory: global warming, caused at least in part by human actions, has changed the climate of our planet. The average global temperature of Earth has increased by at least 1 0 C in the past 100 years. The range of some species has shifted northward in Europe and North America. Slide 28 Because of Their Common Origin, All Living Organisms Share Certain Key Characteristics Slide 29 Living Organism Are Composed of Cells Cells are the foundation for all living things. A cell is a self-contained unit enclosed by a water-repellent layer called the plasma membrane. A bacterium is an example of a single-celled organism. Multicellular organisms are composed of many different kinds of specialized cells working together. Slide 30 All Living Organisms Reproduce Via DNA DNA is genetic material that contains all the instructions for building, maintaining, and growing a cell. In plant and animal cells, DNA is stored within a membrane-bound nucleus. A gene is a segment of DNA that codes for a specific genetic trait (inherited characteristic). * Nucleus: only in some organisms; consists of DNA enclosed within membranes * Slide 31 Living Organisms Transmit Information to the Next Generation (Offspring) in the Form of DNA In sexual reproduction, DNA from two different individuals is combined in the offspring during fertilization. Asexual reproduction does not require fertilization, and results in offspring that are genetically identical to the one parent. Slide 32 All Living Organisms Must Obtain Energy from Their Environment Metabolism is the capture, storage, and use of energy by an organism. Producers obtain energy from the nonliving part of their environment. Consumers obtain energy from the living part of their environment (by consuming producers or other consumers). Slide 33 Living Organisms Sense Their Environment and Respond to It Sharks are more sensitive to electrical fields than any other animal. Electroreceptors on the snout enable sharks to detect minute electrical currents generated by their prey as a side effect of their metabolic processes. Shark attacks destroyed a lot of undersea phone cables in the early years of the telegraph. Slide 34 Living Organisms Maintain Their Internal Conditions Organisms maintain constant internal conditions through a process called homeostasis, despite fluctuations in their external environment. Slide 35 Groups of Living Organisms Can Evolve Biological evolution is a change in the overall genetic characteristics in a group of organisms over the generations. Artificial selection is evolutionary change caused by humans; it occurs when we select plants and animals with preferred traits for breeding. Slide 36 Natural Selection Is an Evolutionary Mechanism That Causes Adaptive Traits to Become More Common over the Generations An adaptive trait is genetic characteristics that enables an individual to survive and reproduce better than its competitors in the population. Slide 37 Natural Selection Produces Adaptation, the Good Match between Organisms and Their Environment All species known to science are given a two-part scientific name, such as Antilocapra americana for the pronghorn. Slide 38 A Population Evolves (Not an Individual) A population is a group of organisms within a species that lives in a particular habitat. A species is a group of organisms that interbreed under natural conditions to produce fertile offspring. A population of pronghorn (Antilocapra americana) in the sagebrush steppes of Wyoming Slide 39 Over Time, Two Populations Can Evolve into Separate Species Populations isolated from one another for a long time may evolve along different paths to become distinctly different Species. All the species on our planet are grouped into three broad categories called domains. Domain Eukarya is divided into four main kingdoms. The tree of life depicts the evolutionary relationship among these domains and their descent from a common ancestor. Slide 40 The Biological Hierarchy Is a Concept Map for Visualizing the Breadth and Scope of Life The biological hierarchy shows the many levels at which biology can be studied. Slide 41 Atoms are the building blocks of matter, which compose the universe. A molecule is created when two or more atoms are held together by chemical bonds. Biomolecules are molecules found in all living cells and generally contain carbon. Slide 42 The cell is the smallest unit of life. Groups of cells that perform a set of unique tasks form a tissue. Different types of tissues make up an organ, which performs a broader range of functions than any of the individual tissue types. Organs are networked into organ systems that come together to form an individual organism. Slide 43 A population is composed of individuals of a single species that interact and interbreed in a shared environment. Populations of different species that live in a shared environment form a biological community. Slide 44 A physical environment and all the communities in it make up an ecosystem. Biomes are large regions of the world that have similar physical characteristics and therefore similar types of organisms. At the highest level of the biological hierarchy, all biomes become part of the biosphere, which is defined as all the worlds living organisms and the places where they live. Slide 45 BIOLOGY MATTERS: SCIENCE AND THE CITIZEN Public-funded research contributes to the advancements of science --basic science --technology Scientific literacy strengthens democracy Slide 46 APPLYING WHAT WE LEARNED: Researches Wrangle over Bacteria Previously, scientists had shown that DNA is made up of hydrogen, oxygen, carbon, nitrogen, and phosphorus atoms The NASA-funded researchers claimed that in the Mono Lake bacteria, arsenic replaces phosphorus in the DNA Evidence offered in support: in the lab, bacteria grow well in phosphorus-free test tubes Critique of the hypothesis and tests: tubes not really free of phosphorus; no phosphorus found in DNA purified from bacterium; no adaptive value for using arsenic in DNA, since theres plenty of phosphorus in Mono Lake The claim is challenged because the tests are not repeatable; alternative hypothesis better explain the observations Mono Lake at Sunset Slide 47 List of Key Terms: Chapter 1 adaptation (p. 19) adaptive trait (p.19 ) Animalia (p. 20) Archaea (p. 20) asexual reproduction (p. 15) atom (p. 20) autotroph (p. 16) behavior (p. 16) biological evolution (p.18 ) biological hierarchy (p. 20) biology (p. 4) biome (p. 22) biomolecule (p.20 ) biosphere (p. 22) cell (p. 15) community (p. 22) consumer (p. 16) control group (p. 12) controlled experiment (p. 12) correlation (p. 11) data (p. 9) dependent variable (p. 12) development (p. 15) DNA (p. 16) domain (p.20) double-blind experiment (p.13) ecosystem (p. 22) Eukarya (p.20) experiment (p. 12) fertilization (p. 15) scientific theory (p. 13) sexual reproduction (p. 15) single-blind experiment (p. 12) species (p. 18) statistics (p. 11) technology (p. 4) tissue (p. 20) treatment group (p. 12) variable (p. 11) Fungi (p. 20) heterotroph (p. 16) homeostasis (p. 16) independent variable (p. 12) individual (p. 22) metabolism (p. 16) microbe (p. 14) molecule (p. 20) multicellular organism (p. 15) natural selection (p. 19) nucleus (p. 16) observation (p. 9) organ (p. 20) organ system (p. 22) photosynthesis (p. 16) placebo (p. 13) placebo effect (p. 13) Plantae (p. 20) plasma membrane (p. 15) population (p. 18) producer (p. 16) prokaryote (p. 20) Protista (p. 20) reproduction (p. 18) science (p. 5) scientific fact (p. 13) scientific hypothesis (p. 6) scientific method (p.5 ) Slide 48 A.hypothesis B.further observations C.experiments D.predictions Observations Test Further tests Revisions Hypothesis supportedHypothesis rejected ? Which word or phrase belongs in the box labeled with a question mark in this concept map of the scientific method? Class Quiz Slide 49 A scientific hypothesis A. must be testable repeatedly and independently. B. cannot be used to generate a prediction because a hypothesis is simply an educated guess. C. is not testable in some disciplines such as astronomy or evolutionary biology. D. can be tested only through experiments, not through observational studies. Class Quiz Slide 50 Reaction time was tested in sleep- deprived Navy Seals trainees. Cadets in three treatment groups ate a snack bar containing 100 300 milligrams of caffeine. Those in the control group ate a snack bar that tasted the same but contained no caffeine. At the time of the test, neither the trainees nor the investigators knew whether a test taker belonged to the treatment group or the control group. Which of the statements that follow is true? A. This is an example of a descriptive observational study. B. Cause and effect cannot be distinguished in such a study. C. This is an example of a double-blind experiment. D. The amount of caffeine consumed is the dependent variable in this study. Class Quiz Slide 51 To test the hypothesis that nitrogen fertilizer improves corn production, agricultural scientists applied different amounts of fertilizer (0 250 kilograms per hectare) to separate corn fields that were planted in exactly the same way with exactly the same variety of corn. At the end of the growing season, the researchers measured the corn yield (kilograms of corn cobs per hectare) and estimated the average number of leaves per corn plant in each corn field. Their data are plotted on this graph. In this study A. there were two variables that the scientist manipulated: corn yield and number of leaves. B. the amount of nitrogen fertilizer added was the independent variable. C. corn yield was the independent variable. D. the control corn field gave the highest yield of corn cobs. Class Quiz Slide 52 Which of the following is a characteristic shared by all living organisms? A. Movement B. Reproduction C. Breathing D. Having a nucleus Class Quiz Slide 53 Relevant Art from Other Chapters and Inside Back Cover All art files from the book are available in JPEG and PPT formats online and on the Instructor Resource Disc Slide 54 Slide 55 Slide 56 Slide 57 Slide 58 1.1 Concept Check 1. What characteristics of the process of science set it apart from other ways of knowing? ANSWER: Scientific knowledge is acquired through evidence, and its objectivity and accuracy are policed through peer review. Slide 59 1.1 Concept Check 2. What mechanisms help bring objectivity to the process of science? ANSWER: Repeatability of observations and experiments, and the requirement for peer-reviewed publication of scientific findings Slide 60 1.2 Concept Check 1. Which type of test would you use to investigate a causal link between two variables: an observational study or an experiment? ANSWER: A controlled experiment Slide 61 1.2 Concept Check 2. How is a control group different from the treatment (experimental) group? ANSWER: The two groups are maintained under identical conditions, except that the independent variable stays constant for the control group, while changing for the treatment group. Slide 62 1.3 Concept Check 1. How is a scientific hypothesis different from a scientific theory? ANSWER: A hypothesis is an educated guess that can be confirmed by observation, experiments, or both. A scientific theory is a major component of knowledge that has been confirmed through extensive testing in many ways by independent researchers. Slide 63 1.3 Concept Check 2. Is anthropogenic climate change an example of a scientific hypothesis, fact, or theory? ANSWER: Theory Slide 64 1.4 Concept Check 1. What is the role of DNA in reproduction? ANSWER: DNA stores information that can be passed from parent to offspring through asexual or sexual reproduction. Slide 65 1.4 Concept Check 2. Are humans producers or consumers in the food web? Why? ANSWER: We are consumers because we must obtain energy from the living, rather than the nonliving, part of our environment. Slide 66 1.5 Concept Check 1. Explain what is wrong with this statement: Over time, a male white-tailed deer evolves larger antlers. ANSWER: An individual deer does not evolve. A population of deer, however, may evolve larger average antler size. Slide 67 1.5 Concept Check 2. Which domain of life do humans belong to? ANSWER: Eukarya Slide 68 1.6 Concept Check 1. How is a population different from a biological community? ANSWER: A population is composed of members of the same species in a shared habitat. A community refers to all members of all species that share a common habitat. Slide 69 1.6 Concept Check 2. Unscramble this scrambled biological hierarchy: community, organ system, ecosystem, atom, tissue, individual, biosphere, organ, cell, biome, population, molecule. ANSWER: Atom, molecule, cell, tissue, organ, organ system, individual, population, community, ecosystem, biome, biosphere