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Biology: The Science of Our Lives
Biology literally means "the study of
life". Biology is such a broad field, covering the minute workings of chemical
machines inside our cells, to broad scale concepts of ecosystems and global
climate change. Biologists study intimate details of the human brain, the
composition of our genes, and even the functioning of our reproductive system.
Biologists recently all but completed the deciphering of the human genome, the
sequence of deoxyribonucleic acid (DNA) bases that may determine much of our
innate capabilities and predispositions to certain forms of behavior and
illnesses. DNA sequences have played major roles in criminal cases (O.J.
Simpson, as well as the reversal of death penalties for many wrongfully
convicted individuals), as well as the impeachment of President Clinton (the
stain at least did not lie). We are bombarded with headlines about possible
health risks from favorite foods (Chinese, Mexican, hamburgers, etc.) as well as
the potential benefits of eating other foods such as cooked tomatoes.
Informercials tout the benefits of metabolism-adjusting drugs for weight loss.
Many Americans are turning to herbal remedies to ease arthritis pain, improve
memory, as well as improve our moods. Can a biology book give you the answers to
these questions? No, but it will enable you learn how to sift through the biases
of investigators, the press, and others in a quest to critically evaluate the
question. To be honest, five years after you are through with this class it is
doubtful you would remember all the details of meatbolism. However, you will
know where to look and maybe a little about the process of science that will
allow you to make an informed decision. Will you be a scientist? Yes, in a way.
You may not be formally trained as a science major, but you can think
critically, solve problems, and have some idea about what science can and
cannoit do. I hope you will be able to tell the shoe from the shinola.
The
Scientific Process
Scientists make progress by using the scientific
method, a process of checking conclusions against nature. After observing
something, a scientist tries to explain what has been seen. The explanation is
called a hypothesis. There is always at least one alternative hypothesis. A part
of nature is tested in a "controlled experiment" to see if the explanation
matches reality. A controlled experiment is one in which all treatments are
identical except that some are exposed to the hypothetical cause and some are
not. Any differences in the way the treatments behave is attributed to the
presence and lack of the cause. If the results of the experiment are consistent
with the hypothesis, there is evidence to support the hypothesis. If the two do
not match, the scientist seeks an alternative explanation and redesigns the
experiment. When enough evidence accumulates, the understanding of this natural
phenomenon is considered a scientific theory. A scientific theory persists until
additional evidence causes it to be revised.Nature's reality is always the final
judge of a scientific theory.
Science is an objective, logical, and
repeatable attempt to understand the principles and forces operating in the
natural universe. Science is from the Latin word, scientia, to know. Good
science is not dogmatic, but should be viewed as an ongoing process of testing
and evaluation. One of the hoped-for benefits of students taking a biology
course is that they will become more familiar with the process of science.
Humans seem innately interested in the world we live in. Young children drive
their parents batty with constant "why" questions. Science is a means to get
some of those whys answered. When we shop for groceries, we are conducting a
kind of scientific experiment. If you like Brand X of soup, and Brand Y is on
sale, perhaps you try Brand Y. If you like it you may buy it again, even when it
is not on sale. If you did not like Brand Y, then no sale will get you to try it
again. In order to conduct science, one must know the rules of the game (imagine
playing Monopoly and having to discover the rules as you play! Which is
precisely what one does with some computer or videogames (before buying the
cheatbook). The scientific method is to be used as a guide that can be modified.
In some sciences, such as taxonomy and certain types of geology, laboratory
experiments are not necessarily performed. Instead, after formulating a
hypothesis, additional observations and/or collections are made from different
localities.
Steps in the scientific method commonly include:
1.Observation: defining the problem you wish to explain.
2.Hypothesis:
one or more falsifiable explanations for the observation.
3.Experimentation:
Controlled attempts to test one or more hypotheses.
4.Conclusion: was the
hypothesis supported or not? After this step the hypothesis is either modified
or rejected, which causes a repeat of the steps above.
After a hypothesis
has been repeatedly tested, a hierarchy of scientific thought develops.
Hypothesis is the most common, with the lowest level ofcertainty. A theory is a
hypothesis that has been repeatedly tested with little modification, e.g. The
Theory of Evolution. A Law is one of the fundamental underlying principles of
how the Universe is organized, e.g. The Laws of Thermodynamics, Newton's Law of
Gravity. Science uses the word theory differently than it is used in the general
population. Theory to most people, in general nonscientific use, is an untested
idea. Scientists call this a hypothesis.
Scientific experiments are also
concerned with isolating the variables. A good science experiment does not
simultaneously test several variables, but rather a single variable that can be
measured against a control. Scientific controlled experiments are situations
where all factors are the same between two test subjects, except for the single
experimental variable. Consider a commonly conducted science fair experiment.
Sandy wants to test the effect of gangsta rap music on pea plant growth. She
plays loud rap music 24 hours a day to a series of pea plants grown under light,
and watered every day. At the end of her experiment she concludes gangsta rap is
conducive to plant growth. Her teacher grades her project very low, citing the
lack of a control group for the experiment. Sandy returns to her experiment, but
this time she has a separate group of plants under the same conditions as the
rapping plants, but with soothing Led Zeppelin songs playing. She comes to the
same conclusion as before, but now has a basis for comparison. Her teacher gives
her project a better grade.
Metric
System Unit System of Measurement
The Metric system was developed in
France during the Nepolianic reign of France in the 1790's. The metric system
has several advantages over the English system which is still in place in the
U.S. However the scientific community has adopted the metric system almost from
its inception. In fact, the metric system missed being nationalized in this
country by one vote in the Continental Congress in the late 1700's or early
1800's. The advantages of the Metric system are: It was based on a decimal
system (ie:powers of ten). Therefore, it simplifies calculations by using a set
of prefixes which we will discuss in a few minutes. It is used by most other
nations of the world, and therefore, it has commercial and trade advantage. If
an American manufacturer that has domestic and international customers is to
compete, they have to absorb the added cost of dealing with two systems of
measurement.
Let's now take a few minutes and speak of the useful set of
"prefixes" used in the metric system sometimes referred to as the System
Internationale (SI). One of the mathematical advantages of the metric system is
its combination of metric terminology with its decimal organization. There are
several prefixes that are associated with a decimal position and can be attached
to the base metric unit in order to create a new metric unit. The knowledge of
the decimal meaning of the prefix establishes the relationship between the newly
created unit and the base unit.
For example: the prefix "kilo" means 103
or 1000 so if I take a mythical base unit like the "bounce" and I attach the
kilo prefix in front, I create a new unit called the "kilobounce". In addition,
the relationship between the two units is now well established. Since I know
that "kilo" means 1000 then one kilobounce unit is the same as (or equal to) 103
bounce units. The prefixes that are most important are listed below along with
their decimal and exponential equivalents:
Prefix decimal
equivalent exponential equivalent
Pico 0.000000000001 10-12
Nano
0.000000001 10-9
Micro 0.000001 10-6
Milli 0.001 10-3
Centi 0.01
10-2
Deci 0.1 10-1
no prefix 1.0 100
Deka 10.0 101
Hecto 100.0
102
Kilo 1000.0 103
Mega 1,000,000. 106
Giga 1,000,000,000. 109
There are several dozen prefixes used but these above are most commonly
used in Science measurements. Now, we will be looking at the metric units of
measurement in five separate areas of measure. The abreviations of each unit
will appear in parenthesis when the unit is first mentioned in the lesson. The
types of measure discussed in this mini-lesson are :
1.Mass
2.Dimension
3.Volume
4.Time
5.Area
The last two will be briefly dealt with.
Mass Measurement
The measure of mass in the metric system has
several units that scientists use most often. The gram is the standard unit of
mass in the metric or SI system. The gram(g or gm) is roughly analogous to the
English dry ounce. It takes about 29 grams to equal one dry ounce. A larger mass
unit analogous to the English pound is the kilogram. The kilogram is the same as
1000 grams and represents 2.2 pounds in mass. Other metric mass units include:
1.the centigram (cg)
2.milligram(mg)
3.microgram mg
4.nanogram(ng).
The basic instrument used to measure mass is the mass
balance. There are some digital balances today that can display the mass of an
object in several different mass units both in the English and Metric systems.
Dimensional Measurement
Now let us go over dimensional measurement that
is measure of length, width, and height. The basic metric unit of dimension is
the meter (m). The meter is analogous to the English yard. A meter is equal to
slightly more than a yard (about 10% larger). One meter is equal to 1.09 yards
or 39.36 inches. A larger metric unit used often is the kilometer(km) which is
analogous to the English mile. One kilometer is equal to 0.62 miles. In
countries where the metric system is the national standard, signposts and posted
speed limits are in km or km per hour. For example, the most common speed limit
in Mexico is 100, but that is 100 km/hr or about 60 miles per hour!! Other
dimensional units include the
1.decimeter(dm)
2.centimeter(cm) which is
analogous to the English inch. One inch is equal to 2.54 cm
3.millimeter(mm)
4.micrometer(mm)
5.nanometer(nm). The nanometer is used when very small
interatomic or intermolecular distances are called for.
The main instrument
in the science lab that measures dimension is the metric ruler. The metric ruler
comes in various sizes. There is the 150 mm ruler and a metric meter ruler which
are used most. However, all metric rulers are calibrated the same. The
numerically numbered positions(major calibrations) are equal to centimeter
marks, and then there are ten equally spaced positions(minor calibrations) in
between each of the numbered positions each of which are equal to 0.1 cm(1 mm).
According to this calibration, one can record measurements with one position of
estimation to the nearest 0.01 cm. Another instrument most often used in Physics
labs is called a micrometer. As the name implies it can measure to the nearest
micrometer and is used for very precise measurements of diameters.
Volume
Measurement
The third type of measure is measure of volume. Actually we can
break this down into the measure of
1.solid volume (regular and irregular)
2.fluid (liquid and gas) volume
Volumes of Regular Solids
Regular
Solids are those that have well defined dimensions of length, width, height, and
diameter. These can first be measured with a suitable dimensional instrument
like a metric ruler. Then a suitable geometrical formula might be applied to get
the volume.
For example, if the solid was rectangular shaped, you would
measure the dimensions of the rectangle and then use the formual V = l X w X h
in order to determine the volume of the rectangle.
Volumes of Irregular
Solids
Irregularly shaped solids do not have well defined dimensions and
therefore can't use the above method of determining its volume. However, one can
use the principle of liquid displacement that says since two chucks of matter
can't occupy the same space at the same time that when placed together one
object will displace the other. If we measure a certain volume of water in a
graduated cylinder to be 5.0 cc and we immerse some pieces of metal into the
water, the reading on the graduated cylinder might read 14.0 cc. By subtracting
the two readings we now have how much displacement of the water there was when
the metal fragments were immersed. That displacement would be equal to the
volume of the metal fragments.
14.0 - 5.0 = 9.0 cc = volume of metal
fragments
Measurement of Fluid Volumes
Let's now discuss measure
of fluid volume. There are several instruments used to directly measure fluid
volumes. The graduated cylinder is the most commonly used in the lab. However,
there are several others. The pipet, buret,and volumetric Flask measure fluid
volumes more precisely than most graduated cylinders. The basic metric unit of
measure for volume is the liter(l) unit. The liter is analogous to the English
quart. One liter being the same as 1.06 quarts. It is basically a fluid volume
unit as is the smaller metric unit called the milliliter(ml). The milliliter is
analogous to the English fluid ounce. One fluid ounce is equal to about 30 ml.
Other metric units of volume that are more often associated with volumes of
solids is the cubic centimeter(cc or cm3) which is equal to a milliliter. To a
careless observer the cc may look like a dimensional unit since it has the word
"centimeter" in it. However, it also has the word "cubic" which always indicates
a volume unit. You can think of a cubic centimeter as a cube 1 cm on each edge.
The volume of such a cube would be 1cm X 1cm X 1cm or 1 cm3. We also use the
cubic meter(m3) often in science to measure large volumes in space. Actually,
any dimensional relationship such as 100 cm = 1 m can be used to derive a volume
unit relationship simply by cubeing BOTH sides of the relationship so for
example:
100 cm = 1 m cubed would be:
(100 cm)(100 cm)(100 cm) =
(1m)(1m)(1m) or 1 X 106 cm3 = 1 m3
You can even do this with English
dimensional relationships that result in a newly created volume relationship.
For example: 1 ft = 12 in. If we cubed both sides we would have: (1 ft)(1 ft)(1
ft)= (12 in)(12 in)(12in) or 1 ft3 = 1728 in3
Area Measurement
Area
measurement relationships are similar to volume relationships except you square
both sides of the dimensional relationship. For example if we wanted to know the
relationship between square cm and square m we could begin with the following
dimensional relationship between cm and m
100 cm = 1 m
Now square bothe
sides
(100 cm)2 = (1 m)2
10,000 cm2 = 1 m2
In summary,
dimensional measurement is one dimensional, area measurement is two dimensional
and volume measurement is three dimensional in scope.