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Scientific method

Understand the scientific method, its importance in distinguishing valid research from propaganda, and how to apply it in various scenarios. Learn about observation, hypothesis, experimentation, and critical thinking skills.

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Scientific method

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  1. Scientific method • Why is it used? • When is it used? • What is it?

  2. Why is the scientific method important? • to distinguish between valid research and propaganda

  3. Observation • The main steps of the scientific method • Feedback • Falsifiable • Testable • Disprovable Question Hypothesis Prediction Test does notsupport hypothesis; revise hypothesis or pose new one Test: Experiment oradditionalobservation Test supports hypothesis; make additional predictions and test them

  4. Experiment Control groups, experimental groups Treatments and levels Quantify results to permit 1. Reproducibility 2. Analysis of results using statistics

  5. Learning to be a Critical Thinker • Become a skeptic • Appreciate the value of statistics • Learn to read graphs • Distinguish anecdotes from scientific evidence • Separate facts from conclusions • Understand the differences between correlation and causation

  6. Figure 2.10x

  7. Classification of organisms into 3 domains

  8. Homo sapiens • Eukaryote - domain • Animalia - kingdom • Vertebrate - subphylum • Mammal - class • Primate - order • Homo - genus

  9. Defining Features of Humans • Bipedalism • Opposable thumbs • Large brain • Capacity for language

  10. ECOSYSTEM LEVELEucalyptus forest • Biosphere • Ecosystem - abiotic factors - all organisms • Community • Population • Organism COMMUNITY LEVELAll organisms ineucalyptus forest POPULATION LEVELGroup of flying foxes ORGANISM LEVELFlying fox Brain Spinal cord ORGAN SYSTEM LEVELNervous system ORGAN LEVELBrain Nerve TISSUE LEVELNervous tissue CELLULAR LEVELNerve cell MOLECULAR LEVELMolecule of DNA Figure 1.1

  11. organ systems • organs • tissues • cells • molecules ECOSYSTEM LEVELEucalyptus forest • Organisms are made up of: COMMUNITY LEVELAll organisms ineucalyptus forest POPULATION LEVELGroup of flying foxes ORGANISM LEVELFlying fox Brain Spinal cord ORGAN SYSTEM LEVELNervous system ORGAN LEVELBrain Nerve TISSUE LEVELNervous tissue CELLULAR LEVELNerve cell MOLECULAR LEVELMolecule of DNA Figure 1.1

  12. biological function starts at the chemical level • Each level of organization builds on the one below it • At each level, new properties emerge ATOMS AND MOLECULES

  13. Atoms consist of protons, neutrons, and electrons • Atom is smallest particle of an element; each element has unique number of protons • Electrical charges of particles 2 Protons Nucleus 2 Neutrons 2 Electrons Figure 2.4A A. Helium atom

  14. An element is a substance that cannot be broken down to other substances by ordinary chemical means • Molecules are combinations of atoms of the same or different elements • Life requires about 25 chemical elements

  15. O, C, H, N , and Ca Table 2.2

  16. Some isotopes are radioactive • Isotopes have a different number of neutrons Table 2.4

  17. Radioactive isotopes can be useful tracers for medical diagnosis Figure 2.5A Figure 2.5B

  18. Electrons are arranged in shells • The outermost shell determines the chemical properties of an atom Outermost electron shell (can hold 8 electrons) Electron First electron shell (can hold 2 electrons) HYDROGEN (H) Atomic number = 1 CARBON (C) Atomic number = 6 NITROGEN (N) Atomic number = 7 OXYGEN (O) Atomic number = 8 Figure 2.6

  19. Free radicals - reversed fountain of youth • Unpaired electron, very reactive • damages DNA in mitochondria, causes artery damage, cancer, speeds aging process • Source: metabolism, sunlight, alcohol, smoking • Neutralized by Vit E, carotenoids, Vit C • Eat your fruits and veggies

  20. Atoms can join with other atoms • Ionic bonds • Covalent bond: polar and nonpolar • Hydrogen bonds

  21. Ions = atoms that gained or lost electrons • An electrical attraction between ions = ionic bond – + Na Cl Na Cl Na Sodium atom Cl Chlorine atom Na+ Sodium ion Cl– Chloride ion Figure 2.7A Sodium chloride (NaCl)

  22. Sodium and chloride ions bond to form sodium chloride, common table salt Na+ Cl– Figure 2.7B

  23. Covalent bonds • atoms share outer shell electrons with other atoms and form molecules • Nonpolar - electrons are shared equally by the atoms • Polar - electrons are unequally shared

  24. Water: What does it have to do with life? • In a water molecule, oxygen forms a polar covalent bond with hydrogen • oxygen exerts a stronger pull on the shared electrons than does hydrogen (–) (–) O H H (+) (+) Figure 2.9

  25. Water’s polarity leads to hydrogen bonding and other unusual properties • The slightly negative O is attracted to the positive H, creating a hydrogen bond Hydrogen bond Figure 2.10A

  26. Hydrogen bonds make liquid water cohesive • surface tension created by cohesive water molecules Figure 2.11

  27. Trees move water because of H-bonds Figure 2.11x

  28. Water’s hydrogen bonds moderate temperature • It takes a lot of energy to disrupt hydrogen bonds • Water absorbs a lot of heat energy with only a small increase in temperature • As water cools, a slight drop in temperature releases a large amount of heat

  29. evaporative cooling • A water molecule takes a large amount of energy with it when it evaporates Figure 2.12

  30. Ice is less dense than liquid water • Molecules in ice are farther apart than those in liquid water Hydrogen bond ICE Hydrogen bonds are stable LIQUID WATER Hydrogen bonds constantly break and re-form Figure 2.13

  31. Frozen water floats (left) and frozen benzene sinks (right) Figure 2.13x2

  32. - Lower water is protected by the surface layer of ice. • Life can survive in cold water underneath ice. • Spring thaw pushes nutrient-rich bottom water to surface

  33. Water is a versatile solvent • Many solutes will stick to polar water molecules and dissolve in water • Metabolic reactions occur in solution Na+ – – Na+ + + Cl– Cl– – – + + – Ions in solution Salt crystal Figure 2.14

  34. solid • liquid • gas • Like no other common substance, water exists in nature in all three physical states: Figure 2.10B

  35. The chemistry of life is sensitive to acidic and basic conditions • A compound that releases H+ ions in solution is anacid, and one that accepts H+ ions in solution is a base. Acid Acid- + H+ Base-+ H+Base

  36. pH scale H+ OH– Increasingly ACIDIC (Higher concentration of H+) • Acidity is measured on the pH scale: • 0-7 is acidic • 8-14 is basic • neutral, pH of 7 Acidic solution NEUTRAL [H+] = [OH–] PURE WATER Human blood Seawater Neutral solution Increasingly BASIC (Lower concentration of H+) Basic solution Figure 2.15

  37. Figure 2.10Bx

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