Lab 1. Introduction: scientific method, measurement, & lab equipment.
Learning objectives:
1. Learn to use metric measurements.
2. Outline the steps of the scientific method; distinguish between observations,
hypotheses, predictions and conclusions; define theory (read section 1.2 in text).
3. Learn to use the microscope, and identify its parts
Metric Measurements: The metric system of measurement is used in science and virtually every other country of the
world. Before proceeding with the microscope exercises, we need to review this system of measurements. Linear,
volumetric, and gravimetric (weight) measurements are all included within the metric system. In microscopic work, we will
only be concerned with linear measurements. Although it’s useful to be able to covert inches and pounds to centimeters
and grams, you should begin to think only in the metric system. Challenge yourself this week, and try to make all of your
estimates of length, weight and volume in metric units, rather than estimating in inches, ounces, and pints.
Obtain a ruler marked in centimeters and millimeters on one side, and inches and their divisions on the other. Compare one
side to the other. One inch equals how many centimeters?
One inch equals how many meters?
To express the size of small objects, such as cell contents, biologists use even smaller units of the metric system than those
on the ruler. These units are the micrometer (m) and the nanometer (nm). Using the information in Table 1, fill in the
following blanks on the relationships of the various units of measure.
1.0 mm =
0.3 mm=
1.6 cm =
5000 nm=
m
m
mm
m=
Table 1. Units of measurement
Unit
Symbol
Meter
Centimeter
Millimeter
Micrometer
Nanometer
Liter
Milliliter
Kilogram
Gram
Milligram mg
Celsius
m
mm
cm
cm
1000 nm=
1500 m=
55 mm=
mm=
Equals
US
m
cm
mm
m
nm
l
ml
kg
g
100 cm
10 mm
1000 m
1000 nm
3.3 feet
0.394 inches
0oC
100 o C
H2O freezes
H2O boils
large
small
1000 ml
1.06 quarts
1 cc (cm3)0.034 oz
1000 g
2.2 lb
1000 mg
0.035 oz
32o F
212 o F
Temperature: Scientists use the Celsius scale. To convert from Fahrenheit to the Celsius scale, use the following equation:
oC = 5 / 9 ( oF – 32o)

Human body temperature of 98o F is what temperature on the Celsius scale?
Record the following temperatures in your lab environment. In each case, allow the end bulb of the Celsius thermometer to
remain in or on the sample for a minute.
o C
o C

Hot tap water =
Cold tap water =


Ice water =
o
C
Skin surface temperature =
o
C
Room temperature =
o
C
Length, Weight & Volume:

Use the balance scale at your workstation to measure the weight of a wooden block to the nearest tenth of a gram.
The weight of the wooden block is
g=
mg.

Using your ruler, measure the length, width and depth of the block.
Length =
cm; width=
cm, & depth=
cm
Now that you have these measurements from the line above, you can calculate the volume, or space, occupied by the
wooden block, expressed in cubic centimeters. Simply multiply: length x width x depth =
cm3
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Usually in biology, we’re measuring liquid volume in liters or milliliters, typically with a graduated cylinder. Take the
graduated cylinder at your workspace, and fill it with 30 ml of water. To do this properly, you have to make sure that the
lowest margin of the water level, or the meniscus, is at the 30 ml mark. See illustration.
Scientific Method: Observation  Question  Hypothesis  Prediction  Experiment / Observation  Conclusion
Two possible outcomes:
1) hypothesis not supported – pose new hypothesis
2) hypothesis supported – make more predictions
Study Figure 1-4 in your text (p. 3). [Your instructor may read several statements to the class, and you can decide where
they fit into the scientific method.] Next, read the following statements and decide if it is an observation (O), hypothesis (H),
conclusion (C), or prediction (P) – label with the appropriate letter.




It is dark in the room because someone turned out the lights.
When the light switch was flipped, the room remained dark – our hypothesis not supported.
It is dark in the room.
If I flip the light switch, the room will no longer be dark.
Read the section on scientific theories on p. 8 – write out in your own words what a theory is. What are the 2 important
theories in biology?
Let’s assume you’ve noticed (i.e. made the observation of) a container of macaroni at your workstation. Use the step-bystep process of the scientific method to answer the question “How many macaroni’s are in the container?” You will need to
make additional observations such as how big or the shape of each macaroni or the shape of the container, etc. Record all
of your observations, hypotheses, experimental design, results, and conclusions below. You may not pour them out &
simply count. You may use anything else in the lab to help you problem-solve, such as individual macaroni’s or empty
containers on the front lab table, rulers to measure the container, and a balance at each work station.
OBSERVATIONS:
HYPOTHESES:
EXPERIMENTAL DESIGN:
RESULTS:
CONCLUSIONS:
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Compound Light Microscope
Humans have good vision, but are blind to some types of radiation that is visible to insects. Humans can hear many
frequencies, but are deaf to ultrasonic frequencies that are perceived by bats. Our sense of taste is mediocre, and our
sense of smell is grossly inferior to cats and dogs. Regardless of our deficiencies, the 5 senses that we have (sight, touch,
smell, taste, and sound) are the major means of acquiring information about the world around us. Biologists must be
observant with all of their senses. Regardless of one’s occupation, a keen sense of observation is necessary for success.
As you saw in the first of today’s lab exercise, observation is the beginning step of the scientific method, and is necessary for
good problem solving skills.
Sometimes the things we want to observe in lab will be too small to see with the naked eye, such as cells and single-celled
organisms, so we will be using a compound light microscope. The slides that you observe will either be prepared slides-representing either a longitudinal or cross section through the tissue or organism—or some slides you will be preparing
yourselves.
Other types of microscopes are used in science; which type you use depends on the size of object you are looking at, and
degree of resolution is needed. The dissecting scope (or stereomicroscope) is used for looking at entire objects in 3D at low
magnification. Also, 2 types of electron microscopes exist – transmission and scanning—that use a beam of electrons rather
than light. See the comparison on page 59 of your text. Electron microscopes are used to view very small objects at greater
detail because of their greater resolving power (see p 62 - 4-4b & p 67 for more examples of SEM images).
Get a compound light microscope out of the cabinet at the back of the room – one per 2 people. Have your instructor model
how to properly carry the microscope – it’s important you don’t drop it or bang it around, microscopes are expensive to
repair/replace! Just a few quick rules for microscope use! – 1- don’t remove any parts of the microscope; 2- the lowest
power objective should be in position at the beginning and end of microscope use; 3- use only lens paper for cleaning lens;
4 - keep the stage clean and dry; 5 - replace the cover after use (keep it dust-free) AFTER returning slides to the front table,
and 6 - report any problems you might have to your instructor.
The first thing you’ll want to do is to identify all of the parts of the microscope. Read the descriptions and see if you can
determine which parts they are on the microscope. Ask your instructor for help if you aren’t sure. They’re here to help you –
don’t be shy! Once you have located them all with your partner, label the diagram below.
Features of the Compound Light Microscope
ARM: supports upper parts and provides a carrying handle; BASE: flat bottom surface of microscope.
LAMP/LIGHT SOURCE: below stage/ source of illumination.
STAGE: flat work surface where the slide may be placed. Some have clips and you move the slide manually; others have
clips and knob used to move the clip, allowing more precise movement of the slide.
DIAPHRAGM: regulates the intensity of the light passing thru the stage aperture and the object. Regulated by a knob under
the stage. As you move it, the view through the oculars becomes brighter or darker.
FOCUS ADJUSTMENT KNOBS: moves the stage and specimen toward or away from the objective lens to sharpen the
image. Some compound scopes have one knob, others have 2, one for coarse focus and one for fine focus.
OCULAR LENS: the ‘eyepiece’ through which you view the object.
OBJECTIVE LENS: lens on revolving NOSEPIECE that provide the initial magnification of object…most scopes have 2-4
objective lens. What are the magnification levels of your objective lens? List below.
x,
x,
x
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This is called a compound light microscope because it has 2 sets of lenses: the ocular (near the eyes) and objectives (near
the object). The object is illuminated from below; light passes up through the clear portions but not the opaque portions of
the object. Many of the prepared slides you will look at will be stained or dyed in order to emphasize different cellular
structures. Look at pictures in your text of microscopic images – there are a lot of them scattered throughout your reading.
Place a plastic ruler (either in your drawer or on front lab bench) on the stage. Look through your lowest power objective
lens – how many lines can you see?
Now switch to a higher power –how many can you see ?
Did your
field of view get larger or smaller as you switched from a lower to higher power?
.
Total magnification:
Total magnification is calculated by multiplying the magnification of the ocular lens by the magnification of the objective lens.
Fill in the following table of total magnification figures for your microscope. The ocular lens for these scopes is 10x, meaning
that particular lens magnifies the object 10 times.
Objective
Scanning power
(lowest)
Low power
Ocular lens magnification
Objective lens magnification
Total magnification
High power
Now you are ready to use the microscope! Send one person up front to obtain the following 2 slides: letter “e” and colored
threads - NOTE : *** The objective lens should never come in contact with anything on the stage. At high magnifications,
the lens will be very close to the slide. Use caution and don’t get in a hurry.

Find the letter “e” with the low power objective lens - does it appear to be right-side-up or up-side-down? Draw
what you see or describe.

Now lower the stage and look at the letter “e” with your ‘naked eye’ - does it appear to be right-side-up or up-sidedown? Draw what you see or describe.
Depth of field: You can also move up and down through some specimens and focus at different levels of the specimen.
Depth of field is the vertical distance that remains in focus at one time. Whatever is in focus at any given level is known as
the plane of focus. To illustrate microscopic depth of field, obtain a slide with 3-4 colored threads mounted together. With
low power, find a point where the threads cross. Slowly focus up and down. Notice that when one thread is in focus, the
others seemed blurred. Determine the order of the threads. Switch to high power and notice that the depth of focus is more
shallow with high power than with low power.
1.

What is the sequence of threads from top to bottom? List the colors starting at the top.--------- 2.
3.
Congratulations, you now know how to use the microscope.  We will be using it throughout the semester. Be sure to take
time to review the parts next week when we look at cells.
Lab review questions – these aren’t to be turned in, just intended to help you study for your lab evaluation.:

2.7 liters equals how many ml?
14 mm equals how many cm?

What is a tentative explanation of observed phenomena?

What step in the scientific method follows experimentation?

What do you call a sample that goes through all the steps of an experiment and does not contain the factor
(variable) being tested?

Can data prove a hypothesis to be true?

Sometimes in biology hypotheses are not well suited to experimental tests? Describe a situation or study in which
a hypothesis could be tested through observation rather than experimentally (see p.6).

What part of the microscope regulates the amount of light?

A virus is 50 nm in size. Which type of microscope should be used to view it?

Why is locating an object more difficult if you start with the high-power objective rather than with the low-power
objective?
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