The Nature of Science

1
The Nature of Science

• Unit I

2
Measurement

• What kind of data can be collected?
• qualitative data
• quantitative data
• What system is used for quantitative data?
• the SI system (metric mostly) uses powers of 10
  and certain prefixes used by scientists
  throughout world to avoid confusion

3
Measurement

• Value (unit)
• Length (meter, m) ?
• Mass (gram, g) ?
• Volume (liter, L) ?
• Time (second, s) ?
• Temperature ? (degree Celsius, C)

• Standard Equipment
• Meter stick, ruler
• Triple-beam balance
• Graduated cylinder, syringe, micropipette
• Stopwatch
• Thermometer

4
Metric Prefixes Values

• the SI system is based on powers of 10
• kilo - hecto - deca - base unit - deci - centi
  milli
• k h D d
  c m
• 1000 - 100 - 10 - -
  1/10 - 1/100 - 1/1000
• Example a kilometer 1000 meters
• How long is a millimeter?
• Is a decaliter larger or smaller than a
  deciliter?
• How many centigrams are in a gram?

5
Metric Conversions

• Because the SI system is based on powers of 10 it
  is easy to convert between units
• kilo hecto deca base unit deci centi
  milli
• King Henry died by drinking chocolate milk
• K -- H -- D -- B -- D -- C -- M
• See demonstration on board

6
Science

• tries to disprove rather than prove
• Difficult to do enough experiments to truly prove
• can be done well, or poorly
• Must examine with a critical eye
• is not democratic
• Based on confirmed observations
• does not follow neat little steps (lab packet)
• Though basic steps always followed

7
Scientific Method
Scientific investigations start with an
observation and a question!
8
Scientific Method

• The following steps will be followed when
  conducting labs in this class
• I. Problem/Purpose
• II. Background/Research
• III. Hypothesis
• IV. Experiment
• V. Data Analysis
• VI. Conclusions
• see Lab Report Format for more specifics!

9
Steps of the Scientific Method

• 1. Problem/Question Develop a question or
  problem that can be solved through
  experimentation.

10
Steps of the Scientific Method

• 2. Observation/Research Make observations and
  research your topic of interest.

11
Do you remember the next step?
12
Steps of the Scientific Method

• 3. Formulate a Hypothesis Predict a possible
  answer to the problem or question.
• Example If soil temperatures rise, then plant
  growth will increase.

13
Steps of the Scientific Method

• 4. Experiment Develop and follow a procedure.
• Include a detailed materials list.
• The outcome must be measurable (quantifiable).

14
Steps of the Scientific Method

• 5. Collect and Analyze Results Modify the
  procedure if needed.
• Confirm the results by retesting.
• Include tables, graphs, and photographs.

15
Steps of the Scientific Method

• 6. Conclusion Include a statement that accepts
  or rejects the hypothesis.
• Make recommendations for further study and
  possible improvements to the procedure.

16
Steps of the Scientific Method

• 7. Communicate the Results Be prepared to
  present the project to an audience.
• Expect questions from the audience.

17
Think you can name all seven steps?
18
Experimental Design

• Large sample size
• Replicated many times
• Control Group
• The baselinewhat results compared against
• Controlled Variables
• Remain the same between all groups, so that they
  are NOT factors in the experiment

19
Experimental Design - Variables

• Independent Variable
• (I set up beforehand)
• is the only variable that is changed between
  experimental groups
• example color of light on plants

• Dependent Variable
• (Data collected During experiment)
• is the effect of the independent variable
• it is what you measure as you experiment
• ex height plants grow

20
Data Tables
Independent Variable (unit) Dependent Variable (unit)




21
Data Tables
Table 1. Height of Sunflowers when Grown in
Varying Colors of Light
Color of Light Sunflower Height (cm)
White (daylight) 7
Red 6
Blue 8
Green 3
22
Graphing Data Tables
Graph 1. Height of Sunflowers when Grown in
Different Colors of Light
Dependent Responds Y axis
Manipulated Independent X axis
23
Graph
Graph 1. Height of Sunflowers when Grown in
Different Colors of Light
Height of Sunflowers (cm)
Color of Light
24
Characteristics of Life

• What processes or traits must all living
  organisms exhibit be considered a live?

25
Characteristics of Life

• How do you know something is alive???
• (With a group of 4 students)
• -Identify the characteristics that are
  common to all living organisms.
• Put your ideas on chart paper
• Be prepared to share your findings with the class

26
Characteristics of Living Things

• Organisms are living things. All living things
• are composed of one or more cells
• contain similar chemicals
• Take in and expend energy
• Grow and develop
• Respond to their surroundings
• Reproduce on the cellular organismal level

27
All Living Things Are Made Of Cells

• A cell is the basic unit of structure and
  function in an organism.
• Unicellular organisms are single-celled
  organisms. Bacteria, the most numerous organisms
  on Earth, are unicellular.
• Multicellular organisms are composed of many
  cells. The cells of organisms use energy to grow
  and repair injured parts.

28
Cells Are Composed Of Similar Chemicals.

• The most abundant chemical in cells is water.
• Another chemical called carbohydrate is a cells
  energy source.
• Proteins and lipids are the building materials
  of cells.
• Nucleic acids are the genetic materials that
  direct the cells activities.

29
All Organisms Need Energy

• Some make their own food (energy)
• Some dont make their own food
• Organisms that can make their own food are called
  autotrophs.
• Organisms that cannot make their own food are
  called heterotrophs.

30
Living Things Grow and Develop

• You werent born being the size you are
  now ZygoteEmbryoFetusNewborn
• InfantToddlerand so on
• Growth is the process of becoming larger.
• Development is the process of change that occurs
  during an organisms life to produce a more
  complex organism.

31
All Organisms React to their Surroundings

• The alternative to responding to your
  surroundings.EXTINCTION!!!
• A change in an organisms surroundings that
  causes the organism to react is called a
  stimulus. An organism reacts to a stimulus with a
  responsean action or change in behavior.

32
All Organisms Can Reproduce

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

33
Pre-AP Bio Exam Review

• Define the independent variable
• Define the dependent variable
• Define experimental group
• Define control group
• Define constants
• Review Safety Symbols Handout
• Identify parts of the scientific method

34

• Interpret data tables and graphs
• Be able to identify and know function of lab
  equipment
• Be able to read lab equipment
• Metric Measurements/Conversions
• Characteristics of Life

35
The Chemistry of Water
36
Why is water essential for life?

• Makes up most content of cells
• Required for chemical reactions
• Required to grow food
• Provides shelter/protection
• Aids in transport of materials

37
Why Water?

• Water is neutral, but its electrons are a little
  off-set
• The oxygen side is slightly negative
• The hydrogen side is slightly positive
• This is called POLARITYit is the key to almost
  all of waters special traits!

38
Properties of waterPolarity

• Waters polarity allows for hydrogen bonds
• These H-bonds make water stick to itself and
  many other thingsresulting in its special
  properties

39
Properties of waterCohesion Adhesion

• What?
• Attraction between water and itself (or another
  molecule)
• Why?
• Polar ends grab each other
• Ex
• Water moving up a stem

40
Properties of waterHigh Surface Tension

• What?
• Difficult to break surface of water
• Why?
• H-bonds make water stick to itself
• Ex
• Insects walking on water

41
Properties of waterHigh Specific Heat

• What?
• Water holds its temp is hard to change it
• Why?
• Must break H-bonds for water to change temp
• Ex
• Bodies of water maintain stable envir. temps
  temps within organisms remain stable

42
Properties of waterHigh Heat of Vaporization

• What?
• Must remove lots of heat before water vaporizes
• Why?
• Must break all H-bonds holding molecules first
• Ex
• Cooling systems in animals

43
Properties of waterIce Less Dense Than Liquid
Water

• What?
• Ice will float in water
• Why?
• H-bonds hold water molecules farther apart (more
  volume)
• Ex
• Ponds insulated in
• winter

44
Properties of waterIce Less Dense than Liquid
Water
45
Properties of waterUniversal Solvent

• What?
• Water dissolves many substances
• Why?
• Charged ends pull on other charged particles
• Ex
• Most rxns require chemicals in solution

46
Water is neutralso why does it have charges?

• Water dissociates into ions
• (ions are particles with charges)
• Not very many ions actually form, but it is
  enough to matter

47
Dissociation of Water

• In pure water H OH-which means pH is 7,
  or neutral
• When acids dissolve in water
• there are more Hs than OHs
• When bases dissolve in water
• there are fewer Hs than OHs

48
How do we know how acidic orbasic something is?

• pH scale measures how acidic/basic
• Scale is 0-14 Neutral 7
• Acid lt 7 Base gt 7
• Each is 10X greater than next
• Ex pH 3 is 10X more acidic than pH 4
• how much more acidic is pH 2 than pH 5?

49
pH Scale
50
Why does pH matter to life?

• Most cells are at pH of about 7
• Even slightest change in pH can be harmful/deadly
  because chemical rxns can be altered/inhibited
• Acid rain harmful because organisms forced to
  take in acidic waterformed when fossil-fuels
  react with water in air

51
Acid Rain
52
The End