Performance Benchmark N.12.A.6
Students know organizational schema can be used to represent and describe relationships of
sets. E/S
Humans are bombarded with information constantly. It is human nature to organize this
information into units based upon similarities and differences to decipher patterns, apply
meaning, and draw conclusions. For example, books can be separated into non-fiction and
fiction. The non-fiction books can be further divided into more specific topics such as sports,
nature, or social sciences. The Dewey Decimal System was designed to apply order to an ever
expanding world of knowledge. It divides book topics into ten main numeric categories. Each
category is further divided into ten subcategories which are divided into ten subdivisions. For
example, all of the 500s represent science topics, the 570s represent life sciences, and 577 is
where you would find books about ecology. By understanding the classification schema of the
Dewey Decimal System, anyone can easily access desired information held within a library. The
internet has been growing nearly exponentially since its inception. The information in the
internet also has an overlaying organization schema. Imagine how long it would take to find the
answer to “How tall is a coastal redwood?” if you had to look through each file on the internet
one at a time. As of February 2007, the Netcraft Web Server Survey found over 108 million
distinct web sites, with 29.7 billion web pages
(http://www.boutell.com/newfaq/misc/sizeofweb.html). Figure 1 shows how the organization of
the internet is expressed in an URL (Uniform Resource Locator) address.
Figure 1. A URL dissected. (from http://21cif.imsa.edu/tutorials/micro/mm/urls/index_html?b_start:int=2)
In science, the objective of all classification systems is to orderly arrange a large array of objects
so that their differences and similarities can be better understood. Classification schema can
facilitate the development of hypothesis, theories, and conclusions. For example, classification
allows scientists to set boundaries to their research by defining which groups are included or
excluded from the study. It also allows scientists to identify patterns within a data set, allows for
extrapolation, and facilitates the communication of results within the framework of a defined
classification system. All fields of science utilize classification schema. For example, biology
classifies species into kingdoms, chemistry classifies matter within the periodic table, physics
classifies energy, and earth science has a classification system of minerals and rocks.
Biology
Scientists have identified approximately 2 million species on Earth and estimate that there may
be as many as 40 million species. Early classification systems separated the known species as
either a plant or animal and further defined animals according to their form of locomotion.
Aristotle classified animals in groups based upon if they could walk, swim, or fly. This early
system had limitations that were hard to overcome. For example, how would birds like penguins
that swim or ostriches that walk be classified? Carolus Linnaeus (1707-1778) published his
Systema Naturae where he proposed an entirely new way to classify plants, based on their
reproductive systems.. Linnaeus’ system was very practical and usable compared to previous
classification systems. His naming method, binomial nomenclature, was later adapted to classify
all life forms. But classification of species is now based on their evolutionary relationships,
determined by genetics, biochemistry, and morphology. Recall, the first classification system
organized life forms into two groups (plant or animal). Figures 2 shows how this classification
system was modified as biologists learned more about the differences between the various life
forms. The two kingdom (Plantae and Animalia) system was expanded to three kingdoms, then
to the traditional five kingdom system. Current comparative genetic studies have allowed
biologists to recognize important distinctions between bacteria and archaea which led to the
proposal of a sixth kingdom system. Figure 3 shows an example of the classification of a single
species from kingdom to species.
Kingdoms and Domains
The three-domain system
Bacteria
Archaea
Eukarya
The six-kingdom system
Bacteria
Archaea
Protista
Plantae
Fungi
Animalia
Plantae
Fungi
Animalia
The traditional five-kingdom system
Monera
Protista
Figure 2. The division of life forms into kingdoms has been modified several times.
(from http://www.bioedonline.org/slides/slide01.cfm?q=%22bacteria%22&dpg=8)
BioEd Online
www.BioEdOnline.org
Figure 3. An example of the classification of a single species.
(from http://www.emc.maricopa.edu/faculty/farabee/biobk/BioBookDivers_class.html)
Chemistry
The periodic table is used in chemistry to compactly show relationships between elements. The
periodic table was developed in 1869 by Dmitri Mendeleev to present all the elements in a way
that shows their similarities and differences. Columns represent elemental groups which have
similar chemical properties. For example, the first column is the alkali metals. Alkali metals are
soft, extremely reactive metals, react with water to form hydrogen gas, and form +1 ions. In
addition to groups, the periodic table is arranged in rows (periods), blocks (based on electron
configuration), and metal/metalloids/non-metals zones. Another level of organization within the
periodic table is the chemical trends. For example, the atomic radius of an atom decreases as
you go across a period. Understanding the layers of information provided in the periodic table, a
chemist knows the main properties of each of the groups in the periodic table and how chemical
properties vary within a group. They can also predict the properties of any particular element
with a reasonable degree of confidence. Figure 4 shows an early version of the periodic table
and Figure 5 provides a current version of the table. This classification schema has evolved
through time and will continue to evolve as new information is discovered.
Figure 4. Dmitri Mendeleev’s 1872 periodic table. (from http://periodic.lanl.gov/mendeleev.htm)
Figure 5. A current Periodic Table. (from http://gpc.edu/~pgore/PhysicalScience/Periodic-table.html)
Physics
Energy may be classified as radiant, chemical, or thermal. This is not the only classification
schema accepted. Energy can also be classified solely as potential or kinetic forms each
expressed more specifically as electrical, mechanical, chemical, or thermal. A third schema is
more delineated as illustrated in Figure 6. This is an example of how multiple classification
systems can be designed to meet the purpose of the user.
Figure 6. An example of how a classification system of the same information can be simple (third column) or
complex (middle column) depending on the needs of the user.
(from http://www.fi.edu/guide/hughes/energytypes10.html)
The example in Figure 6 shows how each of the schema separate the types of energy into
categories based on similarities in properties and then these global groups can be further divided
based on more specific group definition. For example, the electromagnetic spectrum (Figure 7)
was constructed to illustrate how radiant energy is classified by wavelength. The long
wavelengths equals radio waves while very short wavelengths are defined as gamma rays.
Wavelengths between 400 and 750 nm are classified as visible light which can be further
delineated into colors (500-570nm = green) (Figure 8).
Figure 7. The electromagnetic spectrum. (from http://www.nasa.gov/centers/langley/science/FIRST.html)
Figure 8. The electromagnetic spectrum showing the wavelengths of visible light.
(from http://fig.cox.miami.edu/~cmallery/255/255phts/visiblespec.gif)
Earth Science
Earth Science also uses a classification schema to organize a large body of accumulated
knowledge about minerals. There are approximately 3800 known minerals. While this is not as
cumbersome as classifying an animal, it would be near impossible to classify an unknown
mineral sample if an organizational system was not in place. The classification schema for
minerals can be adapted into a mineral identification key that uses the process of elimination to
classify an unknown sample. For example, you can use the table in Figure 9 to identify an
unknown mineral sample provided that your sample is one of the 11 minerals described in this
table. You would first observe if your mineral exhibits cleavage or fracture. Then you would
determine the streak color and continue to test the properties given in the table in order from left
to right using process of elimination to narrow down the possibilities till your arrive at your
mineral name.
Figure 9. An identification table for 11 metallic to submetallic minerals.
(from http://geology.com/minerals/mineral-identification.shtml)
Dichotomous Keys
A dichotomous key is a tool designed by scientists to identify something unknown. Keys may
list a series of statements organized into couplets (Figure 10). For example, one could use the
dichotomous key in Figure 10 to differentiate between four species of birds. Let’s try to identify
Bird X. When using a key, always start at couplet number 1. Does bird X have a beak that is
relatively long and slender or stout and heavy? “b” is the correct choice so we go to step 2. Is
the bottom surface of the lower beak of Bird X flat and straight or curved? Again, “b” is the
correct choice. Go to step 3. Finally, does the lower edge of the upper beak have a distinct bend
or is it mostly flat? Again, “b” is the correct choice. We have identified Bird X as Platyspiza.
Figure 10. A typical dichotomous key.
(from http://www.ekcsk12.org/science/regbio/practicemidterm6.htm)
A dichotomous key may also be presented in pictorial form with paired choices (Figure 11). The
user must choose between the two options given and follow the path through the key to the
correct name of the unknown through the process of elimination.
Figure 11. A pictorial dichotomous key. The user would use this key to identify a type of matter. The first choice
by the user is whether their unknown is a substance or a mixture.
(from http://www.nasaexplores.com/show_912_teacher_st.php?id=040628111348)
Performance Benchmark N.12.A.6
Students know organizational schema can be used to represent and describe relationships of
sets. E/S
Common misconceptions associated with this benchmark:
1. Students incorrectly believe that each classification schema is static.
Any designed classification schema must be flexible to allow the addition of newly
discovered items or relationships. This flexibility not only applies to reorganization of
existing pieces but extends to the addition of completely new categories if something truly
novel is discovered. This idea of an active and adaptable framework not only holds true for
classification schema but applies to all aspects of science. By its very nature, science evolves
as new observations and/or reinterpretations of previous observations.
For greater detail on the nature of science, see the American Association for the
Advancement of Science (AAAS) Benchmarks for Science Literacy On-Line at
http://www.project2061.org/publications/bsl/online/bolintro.htm
2. Students inaccurately believe that there is only one classification schema per discipline.
As discussed above, many classification schemas may be designed to classify the same data
set to meet the needs of the user. It may be extremely simple if only global differences are
important or complicated if more specificity is needed.
Again, for greater detail on the nature of science, see the American Association for the
Advancement of Science (AAAS) Benchmarks for Science Literacy On-Line at
http://www.project2061.org/publications/bsl/online/bolintro.htm
Performance Benchmark N.12.A.6
Students know organizational schema can be used to represent and describe relationships of
sets. E/S
Sample Test Questions
1. Which group of terms is in the correct order from the most general to most specific when
classifying organisms?
a. kingdom, phylum, genus, species
b. species, phylum, genus, kingdom
c. genus, species, kingdom, phylum
d. phylum, kingdom, species, genus
2. Keys are used by biologists to accurately classify unknown organisms such as the
unidentified female mosquito shown in the diagram below. These keys are designed to
categorize organisms according to structural characteristics. The key shows various
characteristics used to identify the difference between Anopheles, Deinocerites, Culex,
Psorophoro and Aedes mosquitoes.
According to the key, which characteristic distinguishes a male from a female mosquito?
a. antennae appearance
b. palp length
c. leg scales
d. abdomen points
3. A student is given a set of objects and is asked to construct a classification scheme to explain
the relationship between the objects. A classification system should be based on
a. Interpretations
b. Observations
c. Hypotheses
d. Inferences
4. The geologic cross sections below represent bedrock from different areas in Earth.
Organizing information in a meaningful way, such as grouping these cross sections, is an
example of
a. classification
b. prediction
c. observation
d. measurement
5. Which statement best illustrates a classification system?
a. A glacier melts at the rate of one meter per year.
b. Ocean depths are measured by using sonar.
c. Snowfall predictions for winter storms vary.
d. Stars are grouped according to their color.
6. The primary purpose of a classification system is to enable people to
a. Eliminate inaccurate inferences
b. Extend their powers of observation
c. Organize observations in a meaningful way
d. Make measurements that are very accurate
7. Which property was probably used to classify the substances below?
Group A
water
gasoline
alcohol
a.
b.
c.
d.
Group B
aluminum
ice
iron
Abundance within the Earth
Specific heat
State (phase) of matter
Chemical composition
Group C
water vapor
air
oxygen
Performance Benchmark N.12.A.6
Students know organizational schema can be used to represent and describe relationships of
sets. E/S
Answers to Sample Test Questions
1.
2.
3.
4.
5.
6.
7.
(a)
(a)
(b)
(a)
(d)
(c)
(c)
Performance Benchmark N.12.A.6
Students know organizational schema can be used to represent and describe relationships of
sets. E/S
Interventions and Strategies and Resources
The following list of intervention strategies and resources will facilitate student understanding of
this benchmark.
1. Classification quiz from The Open Door Web Site
Students need to be given a set of 12 pictures of unknown species. They then use the key
provided at this site to classify each one. Students can then click on the “Wise Owl” and take
a classification quiz.
To access this introduction to classification skills activity, go to
http://www.saburchill.com/questions/class01.html
2. “Classifying and Sequencing Activity” from the National Health Museum
This website provides a series of activities to meet the objectives below. It is not web-based,
but it gives students experience in making observations, grouping objects based on
similarities, and constructing a multistage and serial classification schema.
Objectives of this activity include;
a. “To identify properties that can be used to classify in a binary classification system;
b. To construct a multistage (dichotomous) classification system for a set;
c. To identify properties by which a set can be ordered in a serial fashion and order a set
accordingly.”
To explore this activity, visit
http://www.accessexcellence.com/AE/ATG/data/released/0182-JimMariner/index.html
3. “Potato Chip Classification Activity” from the Educator’s Reference Desk
This is another classroom activity that provides students with experience classifying objects
based on similarities. This activity allows students to classify objects that they are quite
familiar with…Potato Chips!
For a printable copy of this lesson, go to
http://www.eduref.org/cgibin/printlessons.cgi/Virtual/Lessons/Science/Process_Skills/SPS0043.html
4. “Classifying Chemicals Using Properties Activity” from Chemistry and You!
While engaged in this activity, students examine samples of unknown substances with the
purpose of classifying them as either a mechanical mixture, a solution, or a pure substance.
To access this activity, visit
http://www.saskschools.ca/curr_content/science9/chemistry/lesson5.html
5. “Planet Categorization: What is a Planet?” Activity from PBS
This is not a web based activity, but it is a lesson plan with all handouts provided. Centered
in this activity is the Pluto debate and application of the definition of just what it means to be
a planet. The objectives for the lesson include;
1. “To apply astronomy concepts to develop and test a classification system for planets.
2. To participate in a class vote on planet classification.
3. To read an article about astronomers' response to the planetary categorization.
4. To discuss and write an essay about the scientist's role as decision-makers for the public.”
For all of the supporting materials for this activity, go to
http://www.pbs.org/newshour/extra/teachers/lessonplans/science/planet_categorization.html