Scientific method

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 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. Falsifiable: • Hypothesis must be testable. • We try to disprove the hypothesis.

5. jumping spiders and snowberry flies

6. Snowberry flies and jumping spiders

7. Experiment Control groups, experimental groups Treatments and levels Quantify methods and results: why? • - Reproducibility • - Analysis of results using statistics

8. 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

9. Figure 2.10x

10. Classification of organisms into 3 domains

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

12. ECOSYSTEM LEVELEucalyptus forest • Biosphere • Ecosystem - abiotic factors living 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

13. 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

14. 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

15. 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

16. 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

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

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

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

20. 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

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

22. 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)

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

24. 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

25. 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

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

27. 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

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

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

30. 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

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

32. 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

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

34. - 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

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

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

37. Which element did this damage? Figure 2.16B

38. 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

39. pH scale H+ OH– Lemon juice; gastric juice Increasingly ACIDIC (Higher concentration of H+) Grapefruit juice • Acidity is measured on the pH scale: • 0-7 is acidic • 8-14 is basic • neutral, pH of 7 Acidic solution Tomato juice Urine NEUTRAL [H+] = [OH–] PURE WATER Human blood Seawater Neutral solution Increasingly BASIC (Lower concentration of H+) Milk of magnesia Household ammonia Household bleach Oven cleaner Basic solution Figure 2.15

40. Connection: Acid rain threatens the environment Acid rain is formed when air pollutants from burning fossil fuels combine with water vapor in the air to form sulfuric and nitric acids Figure 2.16A

41. Acid precipitation damage to trees Figure 2.16x1

42. Figure 2.10Bx