The Nature of ScienceThe Nature of ScienceUnit IUnit I

MeasurementMeasurement

What kind of data can be collected?

qualitative dataqualitative data quantitative dataquantitative data

What system is used for quantitative data? the the SI system (metric mostly) uses powers of 10 (metric mostly) uses powers of 10

and certain prefixes; used by scientists and certain prefixes; used by scientists throughout world to avoid confusionthroughout world to avoid confusion

MeasurementMeasurement

Value (unit)Value (unit) Length (meter, m) Length (meter, m) Mass (gram, g) Mass (gram, g) Volume (liter, L) Volume (liter, L)

Time (second, s) Time (second, s) Temperature Temperature

(degree Celsius, C) (degree Celsius, C)

Standard EquipmentStandard Equipment Meter stick, rulerMeter stick, ruler Triple-beam balanceTriple-beam balance Graduated cylinder, Graduated cylinder,

syringe, micropipettesyringe, micropipette StopwatchStopwatch ThermometerThermometer

Metric Prefixes & ValuesMetric Prefixes & Values

the SI system is based on powers of 10the SI system is based on powers of 10 kilo - hecto - deca - base unit - deci - centi – millikilo - hecto - deca - base unit - deci - centi – milli k h D *** d c m k h D *** d c m 1000 - 100 - 10 - *** - 1/10 - 1/100 - 1/10001000 - 100 - 10 - *** - 1/10 - 1/100 - 1/1000

Example: a kilometer = 1000 metersExample: a kilometer = 1000 meters How long is a millimeter?How long is a millimeter? Is a decaliter larger or smaller than a deciliter?Is a decaliter larger or smaller than a deciliter? How many centigrams are in a gram?How many centigrams are in a gram?

Metric ConversionsMetric Conversions

Because the SI system is based on powers of Because the SI system is based on powers of 10 it is easy to convert between units10 it is easy to convert between units

kilo – hecto – deca – base unit – deci – centi – millikilo – hecto – deca – base unit – deci – centi – milli

““King Henry died by drinking chocolate milk”King Henry died by drinking chocolate milk” K -- H -- D -- B -- D -- C -- MK -- H -- D -- B -- D -- C -- M See demonstration on board…See demonstration on board…

Science… Science…

……tries to disprove rather than provetries to disprove rather than prove Difficult to do enough experiments to truly proveDifficult to do enough experiments to truly prove

……can be done well, or poorlycan be done well, or poorly Must examine with a critical eyeMust examine with a critical eye

……is not democraticis not democratic Based on confirmed observationsBased on confirmed observations

……does not follow neat little steps (lab packet)does not follow neat little steps (lab packet) Though basic steps always followed…Though basic steps always followed…

Scientific Scientific MethodMethod

Scientific investigations start with an observation

and a question!

Scientific MethodScientific Method The following steps will be followed when The following steps will be followed when

conducting labs in this class…conducting labs in this class… I. Problem/PurposeI. Problem/Purpose II. Background/ResearchII. Background/Research III. HypothesisIII. Hypothesis IV. ExperimentIV. Experiment V. Data AnalysisV. Data Analysis VI. ConclusionsVI. Conclusions

~ see Lab Report Format for more specifics!~ see Lab Report Format for more specifics!

Steps of the Steps of the Scientific MethodScientific Method

1. 1. Problem/QuestionProblem/Question: : Develop a Develop a question or problem that can question or problem that can

be solved through be solved through experimentation.experimentation.

Steps of the Steps of the Scientific MethodScientific Method

2. 2. Observation/ResearchObservation/Research: : Make Make observations and research observations and research

your topic of interest.your topic of interest.

Do you remember the Do you remember the next step?next step?

Steps of the Steps of the Scientific MethodScientific Method

3. 3. Formulate a HypothesisFormulate a Hypothesis: : Predict a possible answer to Predict a possible answer to

the problem or question.the problem or question.

Example:Example: If If soil temperaturessoil temperatures rise, then rise, then plant growthplant growth will will

increase.increase.

Steps of the Steps of the Scientific MethodScientific Method

4. 4. ExperimentExperiment: : Develop and Develop and follow a follow a procedureprocedure..

Include a detailed Include a detailed materialsmaterials list. list.

The outcome must be The outcome must be measurable (quantifiable).measurable (quantifiable).

Steps of the Steps of the Scientific MethodScientific Method

5. 5. Collect and Analyze ResultsCollect and Analyze Results: : Modify the procedure if Modify the procedure if

needed.needed.

Confirm the results by retesting.Confirm the results by retesting.

Include tables, graphs, and Include tables, graphs, and photographs.photographs.

Steps of the Steps of the Scientific MethodScientific Method

6. 6. ConclusionConclusion: : Include a Include a statement that accepts or statement that accepts or

rejects the hypothesis.rejects the hypothesis.Make recommendations for Make recommendations for

further study and possible further study and possible improvements to the improvements to the

procedure.procedure.

Steps of the Steps of the Scientific MethodScientific Method

7. 7. Communicate the ResultsCommunicate the Results: : Be Be prepared to present the project prepared to present the project

to an audience.to an audience.

Expect questions from the Expect questions from the audience. audience.

Think you can name all Think you can name all seven steps?seven steps?

Experimental DesignExperimental Design Large sample sizeLarge sample size

Replicated many timesReplicated many times

Control GroupControl Group The “baseline”…what results compared againstThe “baseline”…what results compared against

Controlled VariablesControlled Variables Remain the same between all groups, so that Remain the same between all groups, so that

they are NOT factors in the experimentthey are NOT factors in the experiment

Experimental Design - VariablesExperimental Design - Variables

Independent VariableIndependent Variable

(“(“II” set up beforehand)” set up beforehand)

~ is the only variable that ~ is the only variable that is changed between is changed between experimental groupsexperimental groups

~ example: color of light ~ example: color of light on plantson plants

Dependent VariableDependent Variable

(“(“DData” collected ata” collected ““DDuring” experiment)uring” experiment)

~ is the effect of the ~ is the effect of the independent variableindependent variable

~ it is what you measure ~ it is what you measure as you experimentas you experiment

~ ex: height plants grow~ ex: height plants grow

Data TablesData Tables

Independent Variable Independent Variable (unit)(unit)

Dependent Variable Dependent Variable

(unit)(unit)

Data TablesData Tables

Color of LightColor of Light Sunflower Height (cm)Sunflower Height (cm)

White (daylight)White (daylight) 77

RedRed 66

BlueBlue 88

GreenGreen 33

Table 1. Height of Sunflowers when Grown in Varying Colors of Light

Graphing Data TablesGraphing Data Tables

0

1

2

3

4

5

6

7

8

9

white red blue green

Column 1

Manipulated

Independent

X axis

Dependent

Responds

Y axis

Graph 1. Height of Sunflowers when Grown in Different Colors of Light

GraphGraph

0

1

2

3

4

5

6

7

8

9

white red blue green

Column 1

Color of Light

Height of Sunflowers (cm)

Graph 1. Height of Sunflowers when Grown in Different Colors of Light

Characteristics of LifeCharacteristics of LifeWhat processes or traits must all What processes or traits must all

living organisms exhibit be living organisms exhibit be considered a live?considered a live?

Characteristics of Life…Characteristics of Life…

How do you know something is alive???How do you know something is alive???(With a group of 4 students…)(With a group of 4 students…)

-Identify the characteristics that are -Identify the characteristics that are common to all living common to all living

organisms.organisms.

Put your ideas on chart paper…Put your ideas on chart paper…

Be prepared to share your findings with the Be prepared to share your findings with the class…class…

Characteristics of Living ThingsCharacteristics of Living Things

Organisms are living things. All living Organisms are living things. All living things:things:

1.1. are composed of one or more cellsare composed of one or more cells

2.2. contain similar chemicalscontain similar chemicals

3.3. Take in and expend energyTake in and expend energy

4.4. Grow and developGrow and develop

5.5. Respond to their surroundingsRespond to their surroundings

6.6. Reproduce – on the cellular & organismal levelReproduce – on the cellular & organismal level

All Living Things Are Made Of CellsAll Living Things Are Made Of Cells

A A cellcell is the basic unit of structure and is the basic unit of structure and function in an organism.function in an organism.

Unicellular Unicellular organisms are single-celled organisms are single-celled organisms. Bacteria, the most numerous organisms. Bacteria, the most numerous organisms on Earth, are unicellular. organisms on Earth, are unicellular.

MulticellularMulticellular organisms are composed of organisms are composed of many cells. The cells of organisms use many cells. The cells of organisms use energy to grow and repair injured parts. energy to grow and repair injured parts.

Cells Are Composed Of Similar Cells Are Composed Of Similar Chemicals.Chemicals.

The most abundant chemical in cells is The most abundant chemical in cells is waterwater. .

Another chemical called Another chemical called carbohydratecarbohydrate is a is a cell’s energy source. cell’s energy source.

Proteins and lipidsProteins and lipids are the building are the building materials of cells. materials of cells.

Nucleic acidsNucleic acids are the genetic materials are the genetic materials that direct the cell’s activities.that direct the cell’s activities.

All Organisms Need EnergyAll Organisms Need Energy

Some make their own food (energy)…Some make their own food (energy)…

Some don’t make their own food…Some don’t make their own food…

Organisms that can make their own food Organisms that can make their own food are called are called autotrophsautotrophs. .

Organisms that cannot make their own Organisms that cannot make their own food are called food are called heterotrophsheterotrophs. .

Living Things Grow and DevelopLiving Things Grow and Develop

You weren’t born being the size you are now…You weren’t born being the size you are now…Zygote…Embryo…Fetus…Newborn…Zygote…Embryo…Fetus…Newborn…

Infant…Toddler…and so on…Infant…Toddler…and so on… Growth is the process of becoming larger.Growth is the process of becoming larger.

Development is the process of change that Development is the process of change that occurs during an organism’s life to produce a occurs during an organism’s life to produce a more complex organism.more complex organism.

All Organisms React to their All Organisms React to their SurroundingsSurroundings

The alternative to “responding” to your The alternative to “responding” to your surroundings….EXTINCTION!!!surroundings….EXTINCTION!!!

A change in an organism’s surroundings A change in an organism’s surroundings that causes the organism to react is called that causes the organism to react is called a stimulus. An organism reacts to a a stimulus. An organism reacts to a stimulus with a response—an action or stimulus with a response—an action or change in behavior.change in behavior.

All Organisms Can ReproduceAll Organisms Can Reproduce

Another characteristic of organisms is the ability Another characteristic of organisms is the ability to reproduce, or produce offspring that are to reproduce, or produce offspring that are similar to the parents. similar to the parents.

Pre-AP Bio Exam ReviewPre-AP Bio Exam Review

Define the independent variableDefine the independent variable Define the dependent variableDefine the dependent variable Define experimental groupDefine experimental group Define control groupDefine control group Define constantsDefine constants Review Safety Symbols HandoutReview Safety Symbols Handout Identify parts of the scientific methodIdentify parts of the scientific method

Interpret data tables and graphsInterpret data tables and graphs Be able to identify and know function of Be able to identify and know function of

lab equipmentlab equipment Be able to read lab equipmentBe able to read lab equipment Metric Measurements/ConversionsMetric Measurements/Conversions Characteristics of LifeCharacteristics of Life

The Chemistry of WaterThe Chemistry of Water

Why is water essential for life?Why is water essential for life?

Makes up most content of cellsMakes up most content of cells

Required for chemical reactionsRequired for chemical reactions

Required to grow foodRequired to grow food

Provides shelter/protectionProvides shelter/protection

Aids in transport of materialsAids in transport of materials

Why Water?Why Water? Water is neutral, but its electrons are a little Water is neutral, but its electrons are a little

off-setoff-set The oxygen side is slightly negativeThe oxygen side is slightly negative The hydrogen side is slightly positiveThe hydrogen side is slightly positive This is called POLARITY…it is the key to almost This is called POLARITY…it is the key to almost

all of water’s special traits!all of water’s special traits!

Properties of water:Properties of water:PolarityPolarity

Water’s polarity allows Water’s polarity allows for “hydrogen bonds”for “hydrogen bonds”

These H-bonds make These H-bonds make water “stick” to itself water “stick” to itself and many other and many other things…resulting in its things…resulting in its special propertiesspecial properties

Properties of water:Properties of water:Cohesion & AdhesionCohesion & Adhesion

What?What?Attraction between water and itself (or Attraction between water and itself (or another molecule)another molecule)

Why?Why?Polar ends grab each otherPolar ends grab each other

Ex:Ex: Water moving up a stemWater moving up a stem

Properties of water:Properties of water:High Surface TensionHigh Surface Tension

What?What?

Difficult to break surface of waterDifficult to break surface of water Why?Why?

H-bonds make water stick to itselfH-bonds make water stick to itself Ex:Ex:

Insects walking on waterInsects walking on water

Properties of water:Properties of water:High Specific HeatHigh Specific Heat

What?What?

Water holds its temp; is hard to change itWater holds its temp; is hard to change it Why?Why?

Must break H-bonds for water to change tempMust break H-bonds for water to change temp

Ex:Ex:

Bodies of water maintain stable envir. temps; temps Bodies of water maintain stable envir. temps; temps within organisms remain stablewithin organisms remain stable

Properties of water:Properties of water:High Heat of High Heat of VaporizationVaporization

What?What? Must remove lots of heat before water Must remove lots of heat before water vaporizesvaporizes

Why?Why? Must break all H-bonds holding molecules firstMust break all H-bonds holding molecules first

Ex:Ex: Cooling systems in animalsCooling systems in animals

Properties of water:Properties of water:Ice Less Dense Than Liquid WaterIce Less Dense Than Liquid Water

What?What? Ice will float in waterIce will float in water

Why?Why? H-bonds hold water molecules farther H-bonds hold water molecules farther apart (more volume)apart (more volume)

Ex: Ex: Ponds insulated inPonds insulated in

winterwinter

Properties of water:Properties of water:Ice Less Dense than Liquid WaterIce Less Dense than Liquid Water

Properties of water:Properties of water:Universal SolventUniversal Solvent

What?What? Water dissolves many Water dissolves many substancessubstances

Why?Why? Charged ends pull on Charged ends pull on other charged particlesother charged particles

Ex:Ex: Most rxns require Most rxns require chemicals in solutionchemicals in solution

Water is neutral…so why does it Water is neutral…so why does it “have charges”?“have charges”?

Water dissociates into ions Water dissociates into ions (ions are particles with charges)(ions are particles with charges)

Not very many ions actually form, but it is enough to matterNot very many ions actually form, but it is enough to matter

Dissociation of WaterDissociation of Water

In pure water [H+] = [OH-]…which means In pure water [H+] = [OH-]…which means pH is 7, or pH is 7, or neutralneutral

When When acidsacids dissolve in water dissolve in water

……there are more H’s than OH’sthere are more H’s than OH’s When When basesbases dissolve in water dissolve in water

……there are fewer H’s than OH’sthere are fewer H’s than OH’s

How do we know how acidic orHow do we know how acidic orbasic something is?basic something is?

pH scale measures how acidic/basicpH scale measures how acidic/basic Scale is 0-14 Neutral = 7Scale is 0-14 Neutral = 7 Acid < 7 Base > 7Acid < 7 Base > 7

Each # is 10X greater than next #Each # is 10X greater than next # Ex: pH 3 is 10X more acidic than pH 4Ex: pH 3 is 10X more acidic than pH 4

……how much more acidic is pH 2 than pH 5?how much more acidic is pH 2 than pH 5?

pH ScalepH Scale

Why does pH matter to life?Why does pH matter to life?

Most cells are at pH of about 7Most cells are at pH of about 7

Even slightest change in pH can be Even slightest change in pH can be harmful/deadly because chemical rxns can harmful/deadly because chemical rxns can be altered/inhibitedbe altered/inhibited

Acid rain harmful because organisms Acid rain harmful because organisms forced to take in acidic water…formed forced to take in acidic water…formed when fossil-fuels react with water in airwhen fossil-fuels react with water in air

Acid RainAcid Rain

The EndThe End