Changing the Story

Changing the Story

Background:

Biology information has undergone dynamic growth in the last two decades as technology has enabled researchers to more effectively and efficiently delve into differences and discrepancies on a molecular scale. Explosions in the amount of information available to present in biology classrooms has changed the number of topics and depth of coverage for those topics. Teachers have to make decisions as to what to add and what to delete from their curricula based on Institutional and District standards tempered by current acceptance of new summaries. In addition, teachers have to constantly monitoring the changing stories in concepts and processes that are the result of new information and then incorporate the changes into the stories developed in the classroom.

To give you an example of what I mean, please try the following:

How many of you eat canned tuna?

What brand do you use and what type?

Describe how you made the choice.

Let me share with you a discussion that Joyce and I have been having based on an article she shared with me.

Advantages of eating tuna:

Molecules in tuna boosts neural development in babies, protect the hearts and brains of adults

Source of : high quality protein, vitamin D, iron, omega-3 fatty acids

Low in saturated fats

Can tuna be considered a health food?

Risks:

Methylmercury is a neurotoxin but adults can remove it from blood although it takes a long time (years)

Methylmercury is toxic to the developing nervous system

Methylmercury levels in fish can be high enough to cause harm

Current Story:

Intake of mercury in excess of one part per million is dangerous to human health.

At that level and above, the U.S. Food and Drug Administration can remove a product from the market.

New Data:

1.                   Collected by Lowenstein and colleagues from Columbia University and reported in April, 2010. They based their recommendations on 100 samples of sushi collected from supermarkets and restaurants in NY, NJ, and CO. They used genetic analysis to identify species and identified samples from bigeye, bluefin, and yellowfin tuna. Their findings showed:

a.        Mercury levels above 1 part per million in samples from 15 of the 54 restaurants tested.

b.      Mercury content varied among species according to size with bigger fish accumulating more mercury

c.       As size increases from yellowfin to bluefin to bigeye, so does the level of mercury

2.      Gerstenberger and colleagues from University of Nevada tested 155 cans of solid-white, chunk-white, and chunk-light tuna of three different national brands for mercury content and reported their results in February, 2010. Their findings showed:

                a. Average mercury levels in all three brands exceeded 0.5ppm

                b. Depending on brand, 4% to 7% of samples exceeded 1 ppm

c. Light tuna, mostly albacore, with 0.28 ppm contained less mercury than chunk-white, mostly skipjack, with 0.5 ppm

Does the story need to be changed? Does the U.S. Food and Drug Administration need to change their recommendations and action level? What do you think?

Recommendations of Researchers:

Add bigeye and bluefin tuna to lists of fish that should be avoided by vulnerable people such as pregnant or nursing women and young children.

Stricter regulations for mercury in canned tuna

When the tuna is 0.5 ppm, a 55 pound child should consume one serving of white tuna every two weeks to be safe

Sources:

Janet Raloff, “Reeling in tuna with lower mercury,” Science News, page10, May 22, 2010

U.S.Food and Drug Administration – www.fda.gov/foodsafety/product-specificinformation/seafood

National Center for Environmental Assessment, EPA – www.ncbi.nlm.nih.gov/pmc/articles/PMC1308510/

Now think of events, concepts or processes, in your field that have changed.

Describe the change.

How have you incorporated the change into your curriculum?

Metaquestion: Please think about this question as I present two examples of changing the story in biology

At what level of education, do educators have to change the story to be more in line with the current accepted summary? In other words, at what grade level do educators who are trying to simplify a complex concept, have to change the story?

Here are two examples in biology that have and will confront me as a teacher.

1-      Due to gene and protein analysis, classification has undergone tremendous change dictating changes in the traditional charts that hang in science classroom at all grade levels. Traditionally, classifications relied on physical, macroscopic evidence. The genome project and techniques of gel electrophoresis and southern blotting have provided information of similarities and differences among living things on the molecular level of genes and their products, proteins. At the time that I received a request to teach AP Biology, textbooks discussed a hierarchical classification that grouped species into increasingly broad categories with the highest or most general being the Kingdom.

See the diagram on the first page of the handout.

 Fortunately in the spring of 1998, I read an article in the Tuesday Science Times summing up the revised story of taxonomy that explained the importance due to prokaryotes that the five kingdom story denied. Molecular evidence gave rise to the three-domain system of Bacteria, Archaea, and Eukarya. The domain is like a superkingdom.  When new information becomes available, teachers have to evaluate the information to determine its importance to the existing stories. Does the new information add detail that students will find valuable to their understanding or does it change the story significantly enough to rework the curriculum.

In the case of the changes in taxonomy, the new system recognized the structural, biochemical and physiological differences between Bacteria and Achaea. Whereas the Bacteria and Achaea had been lumped together in one kingdom equal to the other four, the three domain system recognized that prokaryotes dominate the biosphere. Their collective biomass outweighs all eukaryotes combined at least tenfold.

See the diagram on page two of the handout. It represents a giant shift in our understand of the distribution of life on Earth.

2-      ATP or adenosine triphosphate is a molecule called a nucleotide that is the building block of DNA and RNA. The cool thing is that this building block of DNA in both the part of the whole that makes the genetic code but independently is an energy rich molecule that drives biological reactions and allows cells to do the cell work needed for life.

See the diagrams on pages 3 and 4 of the handout.

For many years, I shared with my students that ATP could not be stored or transported.  ATP represented a form of kinetic energy that was used immediately or lost to the cell. For example, we discussed that solar energy was absorbed by the pigment chlorophyll in plants and some single celled organisms. The absorbed solar energy was transformed into chemical energy in the form of ATP which was used to create carbohydrates. So the solar energy was transformed kinetically into chemical energy stored in the bonds of carbohydrates. This was the story of ATP.

In 1922, two research teams simultaneously showed that an adenosine based purine allowed muscle cells to contract. The information was ignored.

Fifty years ago, another function of ATP was proposed but met with such skepticism that only recently has the idea appeared in the popular science press.  In 1959, Pamela Holton suggested the release of ATP from sensory nerves. In 1962, Burnstock, intrigued by Holton’s work, looked at muscle contractions in the bladder and intestines and discovered evidence of a neural signaling that did not involve the known neurotransmitters of the time. By 1972, he was confident enough to propose the existence of nerves that release ATP as a neurotransmitter.

 The 1990’s brought the technical knowhow to delineate the Human Genome and the discovery for genes that code for the important proteins, such as receptors for neurotransmitters. Having found the genes for ATP receptors allowed scientists to locate the receptors on different types of cells.

See the slide on the last page of the handout. 

The nervous system works by generating electrical impulses along the length of a single neuron. When there is a gap between the end of one neuron and the beginning of the next, a different mechanism is necessary for the signal to cross the gap. The message is then transferred across the gap or synapse by chemical transmitters. There are many known such as acetylcholine and dopamine. The chemical transmitter or neurotransmitter crosses the gap to be received by special proteins in the membrane of the next cell, either a neuron or perhaps a muscle cell. The cell that receives the message will now undergo a change.

Every time there is a change in an accepted story, teachers have to decide if the change is important enough to change the discussion in the classroom. The ATP receptors have been found in plants and primitive life forms such as amoebas and worms. This evidence suggests that this signaling role of ATP appeared very early in the evolution of living things just as the energy role did and supports the idea of the universality of ATP. This is a detail that does not change the story but adds to it. The signaling role of ATP has been observed in the brain, sensory organs and pain pathways, the heart, bone, skin, and the immune system. All of these observations as well as the delineation of the crystal structure of the ATP receptor in 2009, have prompted pharmaceutical companies to pursue the ATP receptors as new drug targets for pain as well as for treating heart and blood vessel disorders and digestive disorders such as irritable bowel syndrome and Crohn’s Disease.

Now that the dual role of ATP has appeared in the popular press, it will appear in the college level biology textbooks in a couple years. At the level of my senior bio class, I will introduce the new story this year using articles such as, “The Double Life of ATP, by Baljit Khakh and Geoffrey Burnstock that appeared in the December 2009 issue of Scientific American.  

This is a new story worth adding to the AP Biology curriculum.

Metaquestion:

At what level of education, do educators have to change the story to be more in line with the current accepted summary? In other words, at what grade level do educators who are trying to simplify a complex concept, have to change the story?

Please take the time to jot down some of your thoughts on this question now.

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