Representing and Applying Data
you read this textbook, you will see many drawings, diagrams, and photographs.
Illustrations help you to understand what you read. Some illustrations
are included to help you understand an idea that you can't see easily
by yourself. For instance, we can't see atoms, but we can look at a diagram
of an atom and that helps us to understand some things about atoms. Seeing
something often helps you remember more easily. The text may describe
the surface of Jupiter in detail, but seeing a photograph of Jupiter may
help you to remember that it has cloud bands. Illustrations also provide
examples that clarify difficult concepts or give additional information
about the topic you are studying. Maps, for example, help you to locate
places that may be described in the text.
illustrations have captions. A caption is a comment that identifies or
explains the illustration. Diagrams, such as the one of the feather, often
have labels that identify parts of the item shown or the order of steps
in a process.
illustration of an organism shows that organism from a particular view
or orientation. In order to understand the illustration, you may need
to identify the front (anterior) end, tail (posterior) end, the underside
(ventral), and the back (dorsal) side of the organism shown.
might also check for symmetry. Look at the illustration on the following
page. A shark has bilateral symmetry. This means that drawing an imaginary
line through the center of the animal from the anterior to posterior end
forms two mirror images.
symmetry is the arrangement of similar parts around a central point. An
object or organism such as a hydra can be divided anywhere through the
center into similar parts.
organisms and objects cannot be divided into two similar parts. If an
organism or object cannot be divided, it is asymmetrical. Regardless of
how you try to divide a natural sponge, you cannot divide it into two
parts that look alike.
illustrations enable you to see the inside of an organism or object. These
illustrations are called sections. Look at all illustrations carefully.
Read captions and labels so that you understand exactly what the illustration
is showing you.
you ever worked on a model car or plane or rocket? These models look,
and sometimes work, much like the real thing, but they are often on a
different scale than the real thing. In science, models are used to help
simplify large or small processes or structures that otherwise would be
difficult to see and understand. Your understanding of a structure or
process is enhanced when you work with materials to make a model that
shows the basic features of the structure or process.
order to make a model, you first have to get a basic idea about the structure
or process involved. You decide to make a model to show the differences
in size of arteries, veins, and capillaries. First, read about these structures.
All three are hollow tubes. Arteries are round and thick. Veins are flat
and have thinner walls than arteries. Capillaries are small.
decide what you can use for your model. Common materials are often best
and cheapest to work with when making models. Different kinds and sizes
of pasta might work for these models. Different sizes of rubber tubing
might do just as well. Cut and glue the different noodles or tubing onto
thick paper so the openings can be seen. Then label each. Now you have
a simple, easy-to-understand model showing the differences in size of
arteries, veins, and capillaries.
other scientific ideas might a model help you to understand? A model of
a molecule can be made from gumdrops (using different colors for the different
elements present) and toothpicks (to show different chemical bonds). A
working model of a volcano can be made from clay, a small amount of baking
soda, vinegar, and a bottle cap. Other models can be devised on a computer.
Some models are mathematical and are represented by equations.
you apply a hypothesis, or general explanation, to a specific situation,
you predict something about that situation. First, you must identify which
hypothesis fits the situation you are considering. People use prediction
to make everyday decisions. Based on previous observations and experiences,
you may form a hypothesis that if it is wintertime, then temperatures
will be lower. From past experience in your area, temperatures are lowest
in February. You may then use this hypothesis to predict specific temperatures
and weather for the month of February in advance. Someone could use these
predictions to plan to set aside more money for heating bills during that
working with large populations of organisms, scientists usually cannot
observe or study every organism in the population. Instead, they use a
sample or a portion of the populate for research. By making careful observations
or manipulating variables with a portion of a group, information is discovered
and conclusions are drawn that might then be applied to the whole population.
work also involves estimating. Estimating is making a judgement about
the size of something or the number of something without actually measuring
or counting every member of a population.
you are trying to determine the effect of a specific nutrient on the growth
of black-eyed susans. It would be impossible to test the entire population
of black-eyed Susans, so you would select part of the population for your
experiment. Through careful experimentation and observation on a sample
of the population, you could generalize the effect of the chemical on
the entire population.
is a more familiar example. Have you ever tried to guess how many beans
were in a sealed jar? If you did, you were estimating. What if you knew
the jar of beans held one liter (1000 mL)? If you knew that 30 beans would
fit in a 100-milliliter jar, how many beans would you estimate to be in
the one-liter jar? If you said about 300 beans, your estimate would be
close to the actual number of beans.
Scientists use a similar process to estimate populations of organisms from bacteria to buffalo. Scientists count the actual number
of organisms in a small sample and then estimate the number of organisms in a larger area. For example, if a scientist wanted to count the number of microorganisms in a petri dish, a microscope
could be used to count the number of organisms in a one square millimeter sample. To determine the total population of the culture, the number of organisms in the square millimeter sample is multiplied
by the total number of millimeters in the culture.