Transcript Chapter 1
Invitation to Biology Chapter 1 Biology Scientific study of life Lays the foundation for asking basic questions about life and the natural world What Am I Doing Here? • To learn how organisms are constructed, how they function, where they live, and what they do • To help develop, modify, and refine ideas about life Impacts, Issues: What Am I Doing Here? Biology is a way of thinking critically about life Biology can help us to better understand human impact on nature, such as an oil field burning out of control during the Persian Gulf War Fig. 1.1, p.2 Life’s Underlying Unity • Life’s organization extends from the molecular level to the biosphere • Shared features at the molecular level are the basis of life’s unity Levels of Organization Life’s levels of organization Molecules of Life • Atoms are the basic units of matter • Living things are made up of a certain subset of molecules: – Nucleic acids – Proteins – Carbohydrates – Lipids Nothing Lives without Energy Energy = capacity to do work Metabolism = processes by which cells acquire and use energy for maintenance, growth, and reproduction Energy Flow • Usually starts with energy from the sun • Transfers from one organism to another • Flows in one direction • Eventually is lost as heat Interdependencies among Organisms Producers Make their own food Consumers Obtain energy by eating other organisms Decomposers Break down remains and wastes Energy input, from sun Producers plants, and other self-feeding organisms Nutrient Cycling Consumers animals, most fungi, many protists, many bacteria Energy output (mainly metabolic heat) Fig. 1-3, p.5 Unity of Life All organisms – Consist of one or more cells – Have the capacity to reproduce based on instructions in DNA – Engage in metabolism – Sense and respond to the environment Homeostasis • Organisms maintain certain conditions in their internal environment • A defining feature of life Life’s Diversity • Millions of living species • Millions more now extinct • Each species has some unique traits Classification Systems • Organisms are grouped into three domains: Eubacteria (Bacteria) Archaebacteria (Archaea) Eukaryotes (Eukarya) Life’s diversity Prokaryotes Eukaryotes • Single celled • Single- or multicelled • No nucleus • Nucleus • Smaller, less complex • Archaebacteria, eubacteria • Larger, more complex • Fungi, protistans, plants, animals Bacteria • The most common prokaryotes Archaea • Prokaryotes Mutation: Source of Variation • Mutation = change in structure of DNA • Basis for variation in heritable traits • May be harmful, neutral, or beneficial Evolution • Heritable change in a line of descent over time • Changes in populations result in diversity Scientific Method • Observe phenomenon • Develop hypotheses • Make predictions • Devise test of predictions • Carry out test and analyze results Role of Experiments • Study a phenomenon under known conditions • Tests the prediction of the hypothesis • Can never prove a hypothesis 100% correct Experimental Design • Control group – A standard for comparison – Identical to experimental group except for variable being studied • Experimental group – Includes one variable being studied Scientific Theory • An explanation of the causes of a wide range of related phenomena • Is consistent with all collected data • Used to make predictions • Still can be disproved Experiments with Synthetic Fat Question: Does Olestra®, a synthetic fat replacement made from sugar and oil, cause intestinal cramps? Designing an Experiment: Olestra ® p.10 Hypothesis Olestra® causes intestinal cramps. Designing an Experiment: Olestra ® Prediction People who eat potato chips made with Olestra will be more likely to get intestinal cramps than those who eat potato chips made without Olestra Experiment Control Group Eats regular potato chips Results 93 of 529 people 89 of 563 people get cramps later get cramps later (17.6%) (15.8%) Experimental Group Eats Olestra potato chips Conclusion Percentages are about equal. People who eat potato chips made with Olestra are just as likely to get intestinal cramps as those who eat potato chips made without Olestra. Stepped Art These results do not support the hypothesis. Fig. 1-8, p.10 Limits of Science • Scientific method – cannot provide answers to subjective questions – cannot provide moral, aesthetic, or philosophical standards – may conflict with supernatural beliefs Limits of Science The external world, not internal conviction, is the testing ground for scientific theories Table 1-1, p.13