Study HabitsStudy Habits
• Find out what works best for YOUFind out what works best for YOU
• Try different methodsTry different methods– Combine methodsCombine methods
• Use shorthandUse shorthand
• Read the chapter BEFORE lecture and be Read the chapter BEFORE lecture and be prepared with any questionsprepared with any questions
• Study EVERY dayStudy EVERY day
What is science?What is science?To Know
• Seeks natural causes to phenomenon– Therefore limited to things that we can OBSERVE
and MEASURE
• Explanatory
• Testable
• Reproducible
• Predictive
• Tentative
What is What is BiologyBiology
• Study of lifeStudy of life– Encompasses Encompasses
• EthologyEthology• Evolutionary BiologyEvolutionary Biology• PhysiologyPhysiology• GeneticsGenetics• Molecular BiologyMolecular Biology• MorphologyMorphology• SystematicsSystematics• EcologyEcology• And more…..And more…..
Approaches
• Discovery- observational– Uses inductive reasoning
• Hypothesis-based- experimental– Uses deductive reasoning
Hypothesis based scienceHypothesis based science
Hypothesis- a tentative statement that proposes a possible explanation to some phenomenon or event – Testable– Tentative relationship is stated– Simple and concise– Falsifiable
• Accept or reject
Prediction vs HypothesisPrediction vs Hypothesis
• Predictions “guess” what will happenPredictions “guess” what will happen
• Hypothesis presents a Hypothesis presents a relationshiprelationship, which , which explains what will happenexplains what will happen– Specific, testable prediction about what will Specific, testable prediction about what will
happenhappen
Language of a hypothesisLanguage of a hypothesis
• Contain the dependent and independent variables
– If leaf color change is affected by (related to) temperature , then exposing plants to low temperatures will result in changes in leaf color.
***If the reader cannot figure out what you are testing, it is not a hypothesis
Scientific TheoryScientific Theory Explanation of something that has Explanation of something that has
been substantiated by a large amount been substantiated by a large amount of data collected over multiple of data collected over multiple experimentsexperiments
Best possible explanation at the time Best possible explanation at the time based on experiments and available based on experiments and available datadata
Can be altered, revised, adapted or Can be altered, revised, adapted or simply abandoned as new data simply abandoned as new data becomes availablebecomes available
Scientific methodScientific method
• ObservationObservation• QuestionQuestion• HypothesisHypothesis• PredictionPrediction• ExperimentationExperimentation
– Controlled Controlled – ReplicationReplication
• Analysis of resultsAnalysis of results• Evaluate hypothesisEvaluate hypothesis• Generate Scientific TheoryGenerate Scientific Theory
ReasoningReasoning
• Inductive- Extrapolate general principles Inductive- Extrapolate general principles from specific examplesfrom specific examples– A conclusion is arrived at based on a set of A conclusion is arrived at based on a set of
observationsobservations
• Deductive- Extrapolate specific Deductive- Extrapolate specific conclusions from general principlesconclusions from general principles– If A then BIf A then B
Reasoning Inductive
All observed crows are black.
Therefore:
All crows are black.
DeductiveAll men are mortal
Socrates is a man
Therefore, Socrates is mortal
Spontaneous GenerationSpontaneous Generation
• Living things arrive from lifeless matterLiving things arrive from lifeless matter– Air had a “life force”Air had a “life force”
• Rotting meat, when left, produced fliesRotting meat, when left, produced flies– Therefore, flies come from rotten meatTherefore, flies come from rotten meat
• Redi’s blowfly experimentRedi’s blowfly experiment
Spontaneous GenerationSpontaneous Generation• Observation- Flies spontaneously appear on rotting
meat
• Question- Does rotting meat produce flies
• Hypothesis- If rotting meat produces flies then any flask with rotten meat will produce flies
• Prediction- A flask of rotting meat will produce flies in 21 days
• Experimentation- 3 jars of meat were subjected to being open, semi-sealed with parchment paper or sealed while other variables remained identical
• Analysis of results- No flies were present in closed jars, semi-closed jars had fly eggs on the parchment
• Evaluate hypothesis against results- Reject hypothesis as sealed jars did not produce flies and semi-sealed jars had fly eggs on the parchment paper
©Barrons 2009
Experiments & TheoriesExperiments & Theories
• Experiments & hypotheses only test Experiments & hypotheses only test NEVER prove theoriesNEVER prove theories
– The very next experiment may falsify theoryThe very next experiment may falsify theory– Always falsify a hypothesis, not prove itAlways falsify a hypothesis, not prove it
Why do I care about Hypothesis testing and scientific method?
• Used in every day life and decision making– Ex: Medical- use scientific method to
determine cause of patients ailment
• Understand the world around us
In-class Exercise
• Get into groups• Each group identify a scientific question,
hypothesis and experimental outcome for each scenario– Don’t worry about figuring out an experiment, just
make up the results of one
• Decide if your outcome supports or refutes your hypothesis
• Scenario 1-While hiking in the forest one day, you notice that while on the left side of the trail, the frogs are bright green, but on the right, they are a mottled green-brown color.
• Scenario 2- As a nurse, one of your patients presents with an unusually low temperature, but no other symptoms
• Scenario 3-You are fishing out in Puget Sound and find that all the other fishermen are pulling up salmon, but you are catching flounder.
Hierarchical organization• Organized according to complexity
• Emergent properties– Properties that were not present at the
previous lower level and result from the specific arrangement and interactions between components
• “The whole is greater than the sum of its parts”
Environmental Interactions• Autotrophs
– Organisms that produce organic compounds from inorganic compounds
• “Producers”• Photosynthesis, chemosynthesis, etc
• Heterotrophs– Organisms that obtain nutrients from other organisms
• “Consumers”
• Decomposers– Decay organic matter, releasing energy back into the
ecosystem• Saprobes
Common features of all living Common features of all living formsforms
• Order/organizationOrder/organization
• RegulationRegulation
• Growth & DevelopmentGrowth & Development
• Energy utilization/processingEnergy utilization/processing
• Response to the environmentResponse to the environment
• ReproductionReproduction
• EvolutionEvolution
Elements of life– Life primarily
consists of C, H, O, N
– Rest are present in small amounts called trace elements
Table 2.1
Trace Elements
• Essential to life
• Occur in minute amounts
• common additives to food and water
• Deficiencies can cause various physiological conditions
Subatomic ParticlesProtons- positive charge
Found in the nucleus
Neutrons- neutral charge
Protons and neutrons occupy the nucleus
Electrons- negative charge
Arranged in electron shells around the nucleus Figure 2.4A
+
+
– –
+
–
2
2
2
Protons
Neutrons
Electrons
Massnumber = 4
+
+
2e–
Electroncloud
Nucleus
Differences in ElementsDifferences in ElementsAtoms of each element
always have the same number of protons
Atomic Number=# protons
Mass Number (atomic weight) = Protons + neutrons
Atoms have no overall charge, thus…
Figure 2.4B
+
–
6
6
6
Protons
Neutrons
Electrons
Mass # = 12
+ +
6e–
Nucleus
Electroncloud
Thus….Thus….Number of protons (+ charge) must be equal Number of protons (+ charge) must be equal
to the number of electrons (-)to the number of electrons (-)
For any element:For any element:
• Number of Protons = Atomic NumberNumber of Protons = Atomic Number
• Number of Electrons = Number of Number of Electrons = Number of Protons = Atomic NumberProtons = Atomic Number
• Number of Neutrons = Mass Number - Number of Neutrons = Mass Number - Atomic NumberAtomic Number
ExampleExample
KrKr
KryptonKrypton
Atomic # = 36Atomic # = 36
Atomic weight = 84Atomic weight = 84
# Protons=?# Protons=?
# Neutrons=?# Neutrons=?
# Electrons=?# Electrons=?
CompoundsCompoundsChemical elements combine in fixed ratios to
form compounds
Different combinations of atoms determine the unique properties of each compound
Sodium Chlorine Sodium ChlorideFigure 2.3
IsotopesIsotopesThe number of neutrons in an atom may vary The number of neutrons in an atom may vary
• Variant forms of an element are called Variant forms of an element are called isotopes isotopes
• Some isotopes are radioactiveSome isotopes are radioactive
Table 2.4
Isotopes
aXz
A = mass number (the total number of protons + neutrons)Z = atomic number (the total number of protons)X = element symbol
Ex: Ordinary hydrogen is written 1H1,
deuterium is 2H1 (heavy water, label in chemistry experiments)
tritium is 3H1 (radioactive)
Radioactive isotopesParticles that are emitted from the nuclei as
a result of nuclear instability
• Irradiation– Disinfestations, pasteurization or sterilization
• Research– Radioactive tracers enable researchers to
follow particular molecules as they undergo change such as through photosynthesis
Usefulness of isotopesUsefulness of isotopes
• Medical DiagnosisMedical Diagnosis– Kidney disordersKidney disorders– Medical ImagingMedical Imaging
• PET scansPET scans
PET scan image of Parkinson's diseased brainBrown.edu 2008
Electrons, Electrons, Electrons!Electrons, Electrons, Electrons!
• The active part of the atomThe active part of the atom– Only part directly involved in chemical activityOnly part directly involved in chemical activity
• Interactions between electrons form chemical Interactions between electrons form chemical bondsbonds
• Electron shellsElectron shells– Arranged in shells, which may contain Arranged in shells, which may contain
different numbers of electronsdifferent numbers of electrons– Shells are “Full” with either 2 or 8 electronsShells are “Full” with either 2 or 8 electrons
Electron arrangement determines the chemical properties of an atom
– Electrons in an atom are arranged in shells, which may contain different numbers of electrons
Hydrogen (H)Atomic number = 1
Electron
Carbon (C)Atomic number = 6
Nitrogen (N)Atomic number = 7
Oxygen (O)Atomic number = 8
Outermost electron shell (can hold 8 electrons)
First electron shell (can hold 2 electrons)
Figure 2.6
Electron Shells
Electron shells• Valence electron shell
– Outermost shell of electrons– These electrons interact with other atoms
Hydrogen (H)Atomic number = 1
Electron
Carbon (C)Atomic number = 6
Nitrogen (N)Atomic number = 7
Oxygen (O)Atomic number = 8
Outermost electron shell (can hold 8 electrons)
First electron shell (can hold 2 electrons)
Figure 2.6
Electronegativity
• Atom’s attraction for shared electronsAtom’s attraction for shared electrons– Greater the electronegativity, stronger the pull Greater the electronegativity, stronger the pull
on e-on e-
Covalent BondsCovalent Bonds•Pairs of e- shared Pairs of e- shared between pairs of between pairs of atomsatoms
–# of bonds is equal # of bonds is equal to additional e- to additional e- necessary to fill the necessary to fill the outer shellouter shell
•Polar and Non-polarPolar and Non-polar
Covalent bond Diamond with 4 covalent bondsinfo.lu.farmingdale.edu/.../atomicbonds.html
PolarityPolarity
• Non-polar covalent- When the atoms exert Non-polar covalent- When the atoms exert a equal pull on the e-a equal pull on the e-– Overall charge of 0Overall charge of 0
• Polar covalent- when the atoms exert an Polar covalent- when the atoms exert an unequal pull on the e-, bond is unequal pull on the e-, bond is – Overall charge on the more electronegative Overall charge on the more electronegative
atom is partially negative and the less atom is partially negative and the less electronegative atom is partially positiveelectronegative atom is partially positive
Polar moleculesPolar molecules
• Unequal e- sharing Unequal e- sharing produces polar bondsproduces polar bonds
(–) (–)
(+) (+)
O
HH
Figure 2.9 Water Molecule
Non-covalent bonds
• Depend on attractive forces between e- of opposite charge– Weak bonds, easily broken and reformed
• Ionic
• Hydrogen
IonsIons
• Created when an atom gains or looses and electron
• Results in an net positive or negative charge depending on if the atom gained or lost the e-
• Anion has neg chrge• Cation has positive charge
Ionic BondsIonic BondsAttractions between ions of opposite chargeAttractions between ions of opposite charge
– An electrical attraction between ions with opposite charges An electrical attraction between ions with opposite charges results in an ionic bondresults in an ionic bond
Transfer of electron
NaSodium atom
ClChlorine atom Na+
Sodium ionCl–
Chloride ion
Sodium chloride (NaCl)
Na Cl ClNa
+ ––
–
Figure 2.7A
NaClNaCl
• Na has 1 e- in the outer shellNa has 1 e- in the outer shell
• Cl has 7 e- in the outer shellCl has 7 e- in the outer shell
• Na “donates” its e- to Cl, leaving Na with Na “donates” its e- to Cl, leaving Na with only 2 shells and Cl with a full outer shellonly 2 shells and Cl with a full outer shell
NaClNaCl
The atom is now an ionThe atom is now an ion– Recall that an ion is an atom or molecule with Recall that an ion is an atom or molecule with
an electrical charge form either gaining or an electrical charge form either gaining or loosing electronsloosing electrons
Hydrogen BondsHydrogen Bonds
• Partial + charge allows shared attractions with – charged molecules
• + charged region always H
Hydrogen bond(+)
(+)
H
H(+)
(+)
(–)
(–)
(–)(–)
O
Figure 2.10
Water and H bonding
1. H2O is asymmetric
2. Each of the two covalent bonds are highly polarized
3. All three atoms are adept at forming H bonds
The importance of hydrogen bonding• Cohesion between HCohesion between H220 molecules0 molecules
– Droplet formationDroplet formation– TransportationTransportation
• Adhesion to substrateAdhesion to substrate• Surface tensionSurface tension• Temperature moderation (body and climatic)Temperature moderation (body and climatic)
– When heated, most thermal E is consumed in disrupting When heated, most thermal E is consumed in disrupting the bonds rather than contributing to molecular motionthe bonds rather than contributing to molecular motion
• DensityDensity– Ice vs. liquid waterIce vs. liquid water
Visual representation of a moleculeVisual representation of a molecule
Molecules can be represented in many ways
Table 2.8
Solvent
• Water is the solvent of life dissolving any charged or polar substances
• Solution
• Aqueous solution
• Solvent– Dissolving agent
• Solute– Dissolved substance
Ph Scale
• Some molecules disassociate and release H+ or OH-
• A compound that releases (donates) H+ ions in solution is an acid– Increases the net H+ ions in solution
• A compound that accepts (removes) H+ ions in solution is a base– Increases the net OH- ions in solution
Ph Scale• 0-14• 7 is neutral• 0-6.9 acidic• 7.1-14 basic/alkaline
• Each unit is 10 fold change in concentration of H+ ions
• Buffers act to minimize Ph changes– React with free H+ of
OH ionsBasic solution
Oven cleaner
Acidic solution
Neutral solution
pH scale0
1
2
3
4
5
6
7
8
9
10
11
12
Lemon juice, gastric juice
Grapefruit juice, soft drink
Tomato juice
Human urine
Pure waterHuman blood
Seawater
Milk of magnesia
Household ammonia
Household bleach
Incr
easi
ngly
AC
IDIC
(Hig
her
conc
entr
atio
n of
H+)
NEUTRAL[H+]=[OH–]
H+ H+
H+ OH– H+
H+ H+
OH– H+ H+
OH–
OH–
H+ H+OH–
OH– OH–
H+ H+H+
OH–
OH–
OH– OH–
OH–OH– H+
Incr
easi
ngly
BA
SIC
(Low
er c
once
ntra
tion
of H
+)
OH–
H+
14
13
CHEMICAL REACTIONSChemical reactions change the composition of matter
reactants products
2 H2O2 2 H2OFigure 2.17A