BIOL110s05-04 - BIOL 110: Principles of Biology Spring 2005...

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Unformatted text preview: BIOL 110: Principles of Biology Spring 2005 Lecture 4, W 1/26/05 Dr. Nathan Staples (Ph.D., UCSB 2002) http://www.smccd.net/accounts/staplesn/biol110/ Don't forget to read and prepare Pre-Lab writeups for Mon./Wed. Labs REVIEW: 1. Classification: 3 domains, 6 kingdoms 1. Prokaryotes (2 domains/kingdoms); 2. Eukaryotes (1 domain; 4 kingdoms) 2. Diversity!! mutation & evolution; Natural selection..... TODAY: Ch. 1: The scientific method experiments Ch. 2: The Molecules of life chemistry Atoms, molecules, water, macromolecules 1 2. Artificial Selection Breeders are selective agents = Breeding!! Individuals exhibiting favored traits are bred Dogs, cats, cattle, date palms, pigeons... Favored traits become more common in population Figure 1.7 2 Table 1.1 Summary of Life's Characteristics Life' Shared characteristics that reflect life's UNITY life' 1. Organisms consist of one or more cells. cells. 2. Organisms are constructed of the same kinds of atoms and molecules according to the same laws of energy. energy. 3. Organisms engage in metabolism; they acquire and use energy metabolism; and materials to survive and reproduce. 4. Organisms sense and make controlled responses to conditions in their internal and external environments. 5. Heritable information encoded in DNA gives organisms a capacity to grow and reproduce. That information also guides the development of complex multi-celled organisms. multi6. Characteristics that define a population of organisms can change change over the generations; the population can evolve. evolve. Table1.1 Page 13 Foundations for life's DIVERSITY life' 1. Mutations (heritable changes in the structure of DNA) give rise to variation in heritable traits, including most details of body form, form, functioning, and behavior. 2. Diversity is the sum total of variations that accumulated in different lines of descent over the past 3.8 billion years, as by by natural selection and other processes of evolution. evolution. III. Scientific Method 1. Observe phenomenon (a recordable event) 2. Develop hypotheses 3. Make predictions 4. Devise test of predictions (more obs; expts) 5. Carry out test and analyze results 6. Form logical conclusions based on results 7. Adapt hypotheses/retest based on results Continuous and Dynamic process!!!..... 3 Role of Experiments Study a phenomenon under known conditions Allow you to predict what will happen if a hypothesis is not wrong Can never prove a hypothesis 100% correct A. Experimental Design 1. Control group: A standard for comparison Identical to experimental group except for variable being studied 2. Sampling error: Nonrepresentative sample skews results Can be minimized by using large samples 4 Draw samples from some aspect of nature CONTROL GROUP The variable being tested is absent EXPERIMENTAL GROUP The variable being tested is present Compile results Compile results Compare and analyze the test results Report on experimental design, test results, and conclusions drawn from results Fig 1.8 Biological Therapy Experiments Can viruses that attack bacteria (bacteriophages) fight infections in mice? 5 Hypothesis: Bacteriophages will kill E.coli in infected mice Prediction: Lab mice injected with bacteriophage will not die after being injected with E.coli Experimental Test: Researchers establish populations of bacteriophage and E.coli. They select a specific strain of laboratory mice. 15 mice injected with E.coli Control group 15 Mice injected with E.coli and bacteriophage Experimental group Test Results All mice die within 32 hours All mice live Figure 1.10 Another Prediction: Bacteriophage will be more effective than a single dose of antibiotics against E.coli Experimental Test: Researchers inject 48 mice with E.coli. Eight hours later: Control - 12 mice injected with saline Expt Group 1 - 12 mice injected with bacteriophage Expt Group 2 - 12 mice injected with streptomycin 60 micrograms/gram Expt Group 3 - 12 mice injected with streptomycin 100 micrograms/gram All die 11 of 12 survive Test Results 3 of 12 survive 5 of 12 survive Figure 1.10 6 B. Scientific Theory 1. An explanation of the causes of a wide range of related phenomena 2. Has wide-ranging explanatory power Is a suitable explanation for a lot of natural phenomena. 3. Still open to testing Example - Darwin's theory of evolution by natural selection C. Minimizing Variables 1. All mice were same age and sex, raised under same conditions 2. Each mouse in each test group received exact same treatment 3. All mice in control group received same amount of saline 4. Variable tested was antibiotic treatment versus bacteriophage treatment 7 D. Limits of Science Scientific approach cannot provide answers to subjective questions Cannot provide moral, aesthetic, or philosophical standards May conflict with supernatural beliefs Scientists Raise Questions The external world, not internal conviction, must be the testing ground for scientific beliefs ** Objective, observable, & recordable data followed with logical conclusions 8 Chapter 2 Molecules of Life Greek Oracle at Delphi (Apollo): Fissures of methane, ethane, and ethylene (sweet smelling) Methane 1. 2. 3. 4. Simplest organic molecule (CH4) A greenhouse gas Main component of natural gas Produced by bacteria in vertebrate gut Flatulence! 5. Found in deep ocean deposits as the world's single largest carbon store ** Lifeless substances (inorganic) are important to us, and knowledge about them can tell us a lot about life!!! 9 I. Elements Fundamental forms of matter Can't be broken apart by normal means 92 occur naturally on Earth Most Common Elements in Living Organisms Oxygen Carbon Hydrogen Nitrogen CHNOPS = in biomolecules 10 What Are Atoms? Smallest particles that retain properties of an element Made up of subatomic particles: 1. Protons (+) 2. Electrons (-) (3. Neutrons (no charge) Examples of Atoms electron proton neutron Hydrogen Helium 11 Isotopes Atoms of an element with different numbers of neutrons Behave the same way in chemical reactions (because same #protons and #electrons) Radioisotopes emit particles and energy as they decay, eventually becoming a different element II. What Determines Whether Atoms Will Interact? The number and arrangement of their electrons 12 Electrons 1. Carry a negative charge (-) 2. Repel one another 3. Are attracted to protons in the nucleus (+) 4. Move in orbitals (volumes of space that surround the nucleus) Electron Orbitals Orbitals can hold up to two electrons Atoms differ in the number of occupied orbitals Orbitals closest to nucleus are lower energy and are filled first 13 Shell Model 1. First shell One orbital Holds as many as 2 electrons 2. Second shell 4 orbitals hold up to a total of 8 electrons 3. Unfilled shells make atoms likely to react OCTET rule: atoms become more stable when have a filled (8e-) outer shell Atoms with nearly 8e- in outer shell grab e-'s strongly; 8eAtoms with few outer shell e-'s tend to give up their e-'s Chemical Bonds, Molecules, and Compounds Bond is union between electron structures of atoms Atoms bond to form molecules Molecules may contain atoms of only one element: O2 Compounds contain more than one element: H2O 14 ...
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