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Tools for a Biologist Chapter 2 | |
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I. Scientific Method
A. STEPS for Scientific Method
1. What is the question? You must first have a problem.
2. Make a hypothesis.
3. Test the hypothesis: using a variable & control.
4. Make a conclusion based on the experiments.B. Theories are explanations that apply to a broad range of activities that are supported experimentally.
C. Scientific Law statement that describes some aspect of a phenomenon that is always true
II. Metric System
A. In science, measurements are expressed in units of the metric system or the International System of Units (Systeme Internationale d'Unites), abbreviated SI.
B. The metric system is a decimal system of weights and measurements. The units of the system are related by factors of ten. Prefixes in the names of the units denote the size of the units.
Prefix Meaning Example Tera- One trillion times (1012) 1 terameter = 1,000,000,000,000 meters (1012 m) Giga- One billion times (109) 1 gigameter = 1,000,000,000 meters (109 m) Mega- One million times (106) 1 megameter = 1,000,000 meters (106 m) Kilo- One thousand times (103) 1 kilometer = 1,000 meters (103) Hecto- One hundred times (102) 1 hectometer = 100 meters (102) Deka- One ten times (101) 1 dekameter = 10 meters (101) Liter, Meter, Grams 1 meter = (100) Deci- One-tenth (10-1) 1 decimeter = 0.1 meter (10-1 m) Centi- One-hundredth (10-2) 1 centimeter = 0.01 meter (10-2 m) Milli- One-thousandth (10-3) 1 millimeter = 0.001 meter (10-3 m) Micro- One-millionth (10-6) 1 micrometer = 0.000001 meter (10-6 m) Nano- One-billionth (10-9) 1 nanometer = 0.000000001 meter (10-9 m) Pico- One-trillionth (10-12) 1 picometer = 0.000000000001 meter (10-12 m)
1. BASE UNITSMeter (m) = length
Liter (L) = volume
Kilogram (Kg) = massVolume Equivalents 1 ml = 1 cm3 (cc)
1 L = 1 dm32. TEMPERATURE
a. Celsius (00C) based on freezing point of H2O = 00C & boiling point of H2O = 1000C
3. FACTOR-LABEL METHOD uses a ratio which is a factor equal to 1 that converts a quantity expressed in one unit to one expressed in another unit.
examples of conversion factors: 1 km = 1000 m 1 mg = .001 g 1 lb. = 16 oz
Sample Problem: Nitrogen gas is the major component of air. A sample of nitrogen gas in a glass bulb weighed 243 mg. What is this mass in SI base units of mass (kilograms)?
Solution: So the conversion in two steps. First convert milligrams to grams; then convert grams to kilograms. To obtain the conversion factor from milligrams to grams, note that the prefix milli- means 10-3. Therefore,
1 mg = 10-3 g243 mg x 10-3 g/ 1 mg = 2.43 x 10-1 g
Then, because the prefix kilo- means 103, we write
1 kg = 103 g
and2.43 x 10-1 g x 1 kg/103 g = 2.43 x 10-4 kg
Note, however, that we can do the two conversions in on step, as follows:
243 mg x 10-3 g/ 1 mg x 1 kg/ 103 g = 2.43 x 10-4 kg
4. SHORT CUT for FACTOR LABEL METHOD
King Henry’s Daughter Makes delicious corn muffins _ _ (m)monday _ _ night kilo- hecta- deka- unit deci- centi- milli- micro- nano- RULE: when you are given a prefix and would like to convert to another unit, start at that prefix given, count the number of prefixes away from the desired prefix and move the decimal that many places in the same direction
Sample Problem) 14.5 mm = ? mm
Solution) Micro(m) is three places away from milli. Move the decimal three places to the left to get the answer.
0.0145 mm
What do scientists use to study cells? III. TYPES of MICROSCOPES
What does a cell look like?
The CELL THEORY states:
1. Cells are the basic units of structure and function of living things.
2. Cells come from preexisting cells.
3. Cells carry out life functions.EXCEPTIONS to the CELL THEORY:
1. If all cells must arise from previously existing cells, there is a question as to the origin of the first cell. Where did it com from? Biologists are still searching for the complete answer.
2. Viruses contain simple genetic material and carry out a type of reproduction, but are not true cells. There is some question as to the status of viruses as "living" organisms, since they apparently do not carry on life functions other than synthesis. Viruses do NOT contain organelles.
3. Certain cell organelles behave like cells in some respects. Both mitochondria & chloroplasts are known to contain genetic material and to produce new organelles like themselves under certain circumstances.A. Simple Microscope- a magnifying glass or hand lens
B. Compound Microscope- produces magnification of 40x (scanning objective), 100x (low power objective) & 430x (high power objective)
STEPS for FOCUSSING the Compound Microscope
1. Position the specimen under scanning.
2. Adjust the diaphragm.
3. Focus using the coarse adjustment.
4. Center specimen.
5. Switch to low power, position specimen and repeat steps 2-4 in order.
6. Switch to high power, position specimen, & adjust the diaphragm.
7. Focus using the fine adjustment.RESOLUTION- is the quality of the compound microscope that makes it possible to see the separatation between objects that are very close together in a microscope field
STAINS- allows normally invisible cell parts to be viewed under the microscope
examples: iodine & methylene blueC. Phase-Contrast Microscope- this microscope can details of cells without staining
D. Stereo Microscope (DISSECTING Microscope)- low power microscope that gives the viewer a three dimensional image for purposes of gross dissection.
E. Electron Microscopes-
1. Transmission Electron Microscope (TEM)- has extremely high maginigication, used to view cell structures (organelles), has resolving power of 0.5 nm
2. Scanning Electron Microscope (SEM)- produces three-dimensional image, has resolving power of 500 nmIV. OTHER TOOLS SCIENTISTS USE for EXPERIMENTS
A. Graduated Cylinder- measures volume, the experimentor must read the meniscus which is the bottom of the curve within the graduated cylinder
B. Centrifuge- is use to separate
C. Ultracentrifuge- a tool used to separate cell parts according to their densities
To view a centrifuge click: http://www.eppendorf.com/eppendrf/bionews/news6.html D. Video Cameras- used to view objects in motion
E. Tissue Cultures- placing living organisms on a medium (containing nutrients & other factors so the organism can survive) outside the body
F. Electrophoresis- technique for separating substances made of particles that have an electrical charge. Used to separate DNA.
G. Microdissection Apparatus- is a small instrument used to operate on cell organelles
Applying MATH to SCIENCE Throughout life you will use math as a tool to solve problems. How does math apply to the light microscope? Solve the following problems to see how math can be used to solve science problems.
1. The diameter of the field of view of a compound light microscope is 2.0 mm. What is the maximum number of pollen grains that could fit along the diameter of this field if each pollen grain has a diameter of 100 mm?
2. A student determined the diameter of the low power field of a compound microscope to be 1.20 mm. What portion of the field diameter would be occupied by an organism that is 600 mm long?
3. A student was observing cells with the microscope and noted that one cell occupied one-quarter of the diameter of the field of view. If the diameter of the field was 1.5 mm, what was the approximate length of the cell?
4. A compound light microscope has lenses that permit 100x under low power and 400x under high power. While looking at some cells under high power, the student observes that four cells extend across the diameter. How many cells could be seen under low power?
return to Mr. Buono's syllabus