Evolution of the Chocolate Bar: Creative Approach to Teaching: Phylogenetic Relationships within Evolutionary Biology

Burks, Romi L. .. .., Boles, Larry C., The American Biology Teacher

Chocolate calms the mind, yet excites the senses. Chocolate also unites cultures. Chocolat (2000), a movie about a small town French chocolate shop, made millions internationally. Starring actors contributed partly to the film's success but the film also drew salivating viewers worldwide to the multiple applications of chocolate. With its stimulant properties, chocolate generally makes people feel good. Chocolate may also inspire creativity. For example, every day biologists can use chocolate's fortunate property of appearing in different shapes, sizes, and compositions to help students understand basic principles of evolution. Few students have visited the Galapagos to see Darwin's finches, but nearly all have sampled a variety of chocolate bars. Using chocolate as a "model organism" can make understanding key elements of evolution more palatable to the student. Chocolate represents an ideal model for exploration because it comes in many variations, some of which make good choices for describing evolutionary history and some of which change too much to be useful. In addition, a little Web research produces a timeline for the debut of different candies (Figure 1) that can lend insight into the construction of evolutionary trees.

Figure 1. abridged history of the chocolate bar and candies.

* 1890 George A. Bayle Jr., of St. Louis, Missouri, packages peanut
butter in barrels and sells it for six cents a pound.

* 1900 Milton S. Hershey of Lancaster, Pennsylvania, introduces the
first Hershey's[R] Milk chocolate bar.

* 1903 George Washington carver researches uses for peanuts. Peanut
butter introduction to the world occurs a year later at the Universal
Exposition in St. Louis.

* 1920 Baby Ruth[R] candy bar is first sold, named for President
Grover Cleveland's daughter.

* 1928 Hershey introduced peanut butter cups later named after Harry
Burnett (H.B.) Reese, a former dairy employee.

* 1930 M & M/Mars introduces the SNICKERS[R] Bar, named for a favorite
horse owned by the Mars family. One candy bar costs a nickel.

* 1941 M & M'S[R] Plain Chocolate Candies (later M & M'S[R] milk
chocolate Candies) introduced.

* 1954 M & M'S[R] Peanut Candies introduced.

* 1978 REESE'S PIECES candy is introduced.

* 1982 REESE'S PIECES candy makes its big screen debut as "E.T.'s"
favorite candy in the movie E.T., The Extra Terrestrial.

* 1981 A European favorite since 1974, SKITTLES[R] Bite Size Candies
are introduced in the U.S. by M & M/MARS.

* 2001 SNICKERS[R] Cruncher premiers.

* 2002 SNICKERS[R] with Almond Bars replace Mars Bar.

* 2004 M & M'S[R] and chocolate bar merge into M-Azing[R] Crunchy and
Peanut Butter versions.

Sources: National Confectioners Association (http://www.candyusa.org/
Classroom/timeline.asp), http://www.peanutbutterlovers.com/history/,
M&M Mars Corporation (http://www.mmmars.com/cai/snickers/faq.html#top,
http://www.snickers.com/history.asp, and http://us.mms.com/us/about/
history/story/)), and Hershey Foods Corporation
(http://www.hersheys.com/consumer/history.shtml;. All candies are
registered trademarks.

Teaching Evolution

The theory of evolution (for bold words, see Figure 2, Glossary) is unfortunately and undeservingly fraught with controversy (Scott & Branch, 2003; Langen, 2004); most of it political (Weis, 2001). Despite its acceptance by the scientific community as the theory that explains how organisms change through time, innumerable debates flourish about when, where, or even why to teach evolution (NAS, 1998; Bybee, 2002). Still, even after one is undeniably convinced of the merits of teaching evolution, the practicality of such a task can be daunting and pose its own unique challenges (Bybee, 2001). Communicating such a monumentally critical theory as evolution may take on its own sense of arduousness, especially when sharing such ideas with newly-minted undergraduates or high school students who may or may not have experienced a progressive biology curriculum (Bybee, 2001; Langen, 2004).

Figure 2. Glossary

* Adaptation--any morphological, physiological, or behavioral
change that enhances survival, growth, and the reproductive
success.

* Character--a feature or attribute that has been selected for
classification purposes, is capable of being measured, and
will have character states.

* Character states--any of the possible distinct conditions
or forms that a character may exhibit.

* Clade--a group of taxa that all share an immediate common
ancestor and therefore are more closely related to each
other than any other taxa.

* Cladistics--a classification method in which the members
of taxa have been grouped together on the basis of phylogenetics,
i.e., the members of the taxa share a more recent
common ancestor with each other than with the other
members of any other group.

* Cladogram--a branching, treelike diagram in which the
endpoints of the branches represent specific taxa of organisms.
With a common bifurcating pattern, it is used to illustrate
phylogenetic relationships and show points at which
various taxa have diverged from common ancestral forms;
cladogenesis = the evolutionary change and diversification
resulting from the branching off of new taxa from common
ancestral lineages.

* Classification--the systematic process of forming and
ordering groups based on similarity.

* Convergence--similarity, especially of function, appearing
in taxa that do not share an immediate common ancestor,
due primarily to similar selective pressures.

* Derived--a character state that is a modified version of the
ancestral state.

* Evolution--change in allele frequencies in a … 

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Publication information: Article title: Evolution of the Chocolate Bar: Creative Approach to Teaching: Phylogenetic Relationships within Evolutionary Biology. Contributors: Burks, Romi L. .. .. - Author, Boles, Larry C. - Author. Journal title: The American Biology Teacher. Volume: 69. Issue: 4 Publication date: April 2007. Page number: 229+. © National Association of Biology Teachers Mar 2009. COPYRIGHT 2007 Gale Group.

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