Human Sense of Smell Is More Sensitive Than You Might Think

ScienceDaily has brought us yet another interesting article related to the National Science Education Standards Life Science Content Standard. My guess is that middle school teachers’ and students’ olfaction capabilities might be a bit superior to the general public’s, given my personal experience in teaching middle school! Nonetheless, scientists from Northwestern University’s School of Medicine report that imperceptible levels of scents affect our judgment in unconscious ways.

The article, Subliminal Smells Bias Perception About A Person’s Likeability, does not explicate the researchers’ questions or hypothesis, but inference indicates their questions were: What concentration levels of scents can people consciously detect? How does scent affect human judgment of the likeability of other humans?

Three scents were used at several levels of concentration, from imperceptible to definitely perceptible. The scents were: “lemon (good), sweat (bad) and ethereal (neutral). . . . Study participants were informed that an odor would be present in 75 percent of the trials.” After participants sniffed a sample, they were shown a photo of a human face with a neutral expression and were asked to rate the person’s likeability along a six-point scale. Though no details are given on how the data was analyzed, the lead author is quoted as saying,

The study suggests that people conscious of the barely noticeable scents were able to discount that sensory information and just evaluate the faces. It only was when smell sneaked in without being noticed that judgments about likeability were biased.

How to Turn This News Event into an Inquiry-Based, Standards-Related Science Lesson

Do your students participate in a Science Day competition or activity? Then you know how hard it can be to help students find a topic they can relate to and apply the methods of science. Sharing this article with your students and accompanying it with a discussion of the methods of science used here might just be the perfect bridge to help your students find an accessible topic. Since particular sample sizes and data analysis methods are not described in the article, you and your students could brainstorm a variety of possible approaches.

You could follow up by going through your local library’s electronic periodical data base to find the researchers’ original report in the December 2007 issue of Psychological Science, “Subliminal Smells Can Guide Social Preferences” by Wen Li, Isabel Moallem, Ken A. Paller, and Jay A Gottfried, and sharing with your students the methods these researchers did use. A discussion of the pros and cons of their methods as compared to those brainstormed by your students could round out your lesson.

The ScienceDaily article can also be used as an introduction to a unit on the senses (i.e., structure and function in living things) or on regulation and behavior, both topics within the NSES Life Science Standard. After sharing the article with students, ask: From an adaptive perspective, what value might there be in this phenomenon of imperceptible levels of scent causing unconscious behavior? Are humans the only organism likely to display this trait? How do you know?

Here are some additional resources that are part of the Middle School Portal 2 collection to facilitate your instruction regarding structure and function in living things, olfaction, methods of science, and regulation and behavior: Structure and Function in Living Systems; Enose Is Enose Is Enose; Discovery, Chance and the Scientific Method; Regulation and Behavior.

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We want and need your ideas, suggestions, and observations. What would you like to know more about? What questions have your students asked? We invite you to share with us and other readers by posting your comments. Please check back often for our newest posts or download the RSS feed for this blog. Let us know what you think and tell us how we can serve you better. We appreciate your feedback on all of our Middle School Portal 2 publications. You can also email us at msp@msteacher.org.

This post was originally written by Mary LeFever and published December 13, 2007 in the Connecting News to the National Science Education Standards blog. The post was updated 4/23/12 by Jessica Fries-Gaither.

Mechanism for Antibiotic Resistance Discovered

Those of us born after World War II have take antibiotics for granted. Strep throat? Ear infection? Acne? Bronchitis? Not a problem. Take the full prescribed antibiotic dose and you are cured. The reality of antibiotic resistant bacteria however, disrupts that scenario. No longer can we always trust in a full recovery from a bacterial infection after completing the antibiotic regimen. Rather than continuing to create new and different antibiotics, the trend in research is to discover the mechanisms of antibiotic resistance in order to neutralize it.

How Some Bacteria Survive Antibiotics from ScienceDaily describes how researchers at the University of Illinois, Chicago, studied bacterial action in the presence of erythromycin and related antibiotics. These drugs incapacitate the bacterial protein factories, ribosomes. All cells have ribosomes which are the site of translation in protein synthesis. Erythromycin prevents newly synthesized proteins from detaching from the two subunits of the ribosome, thus preventing the bacteria from thriving. The researchers discovered, however, that these drugs can signal the bacteria to switch a bacterial gene on that enables bacterial release of newly synthesized proteins from the ribosomes. Thus, they effectively resist the drug in a process known as inducible antibiotic expression.

The article quotes one of the researchers

Combining biochemical data with the knowledge of the structure of the ribosome tunnel, we were able to identify some of the key molecular players involved in the induction mechanism. . . .We only researched response to erythromycin-like drugs because the majority of the genetics were already known. There may be other antibiotics and resistance genes in pathogenic bacteria regulated by this same mechanism. This is just the beginning.

How to Turn This News Event into an Inquiry-Based, Standards-Related Science Lesson

A manifestation of evolution, antibiotic resistance aligns with the Life Science standard of The National Science Education Standards, “Species acquire many of their unique characteristics through biological adaptation, which involves the selection of naturally occurring variations in populations. Biological adaptations include changes in structures, behaviors, or physiology that enhance survival and reproductive success in a particular environment.” Also related is the structure and function section of the standard: prokaryotic cell structure, the ribosome, and protein synthesis.

Ask students if they have ever had an ear infection or strep throat. What did they do about it? Lead them to disclose that they went to the doctor, were prescribed an antibiotic and took it for the full course, often 10 days. Ask if they were cured then, or did anyone suffer a recurrence within the next week or so? If yes, why? Then what did they do? Lead them to articulate the concept of bacterial resistance. Consider showing visuals of a typical animal eukaryotic cell side by side with a bacterial cell. This will highlight the size and structural difference, and enable student comprehension of how bacterial cells can colonize a eukaryotic cell. Make sure they understand the activity of the millions of bacteria cells a) consumes nutrients needed by one’s own healthy cells and b) produces waste that makes one sick.

If you’ve already discussed the characteristics of living things, cell theory and cell structure, lead students to recall the importance of ribosomes to all living cells. Ask, what might happen if the function of the ribosomes were disrupted? Students should reason that protein production would stop and the cell would die for lack of needed proteins. Inform them that this is the way some antibiotics work; they interfere with the bacterial cells’ ribosome function. (Prokaryotic and eukaryotic ribosome structure varies slightly allowing the eukaryotic ribosomes to remain unaffected.) Ask, what if the presence of the antibiotic signaled the bacteria to produce a protein (turn a gene on) that interfered with the drug’s ability to disrupt the ribosome’s work? Allow plenty of wait time for them to think this through logically. They should arrive at the idea of antibiotic resistance, even if they don’t use that phrase.

Allow students to read the first three paragraphs above and follow the links. The protein synthesis link however, is probably too advanced for middle school students and can be eliminated. Have them read the article How Some Bacteria Survive Antibiotics. Assess: what is an antibiotic? How do drugs like erythromycin work? What is inducible antibiotic expression? How might it be helpful to know the mechanisms by which bacteria resist antibiotics? Describe how antibiotic resistance is an example of evolution.

Here are some additional resources from the Middle School Portal 2 related to antibiotic resistance and bacteria: Introduction to Bacteria; Microbes: Too Smart for Antibiotics?; Microbes: What They do and how Antibiotics Change Them; and What’s making you sick?

We Want Your Feedback

We want and need your ideas, suggestions, and observations. What would you like to know more about? What questions have your students asked? We invite you to share with us and other readers by posting your comments. Please check back often for our newest posts or download the RSS feed for this blog. Let us know what you think and tell us how we can serve you better. We appreciate your feedback on all of our Middle School Portal 2 publications. You can also email us at msp@msteacher.org.

This post was originally written by Mary LeFever and published May 9, 2008 in the Connecting News to the National Science Education Standards blog. The post was updated 4/23/12 by Jessica Fries-Gaither.

A Breakthrough in Nerve Cell Regeneration

When you conjure up an image of cells, what do you see? What do you think? You may see a snapshot of an animal tissue, perhaps with actively dividing cells. That’s understandable because, as animals ourselves, we’re aware that cells come from other cells, thus the need to undergo mitosis, or cell division, frequently.

But one kind of mammalian animal cell does not fit that image—nerve cells. They do not arrange themselves as cells in a typical tissue do. Nerve cells are singular, with a long, sometimes very long, threadlike extension called an axon. And they don’t undergo mitosis frequently, except in embryos. This apparent aberration in the world of cells has puzzled scientists and medical researchers. If one could get nerve cells to behave more like other cells in terms of regeneration, a host of nerve-related diseases and damage could be reversed.

ScienceDaily published a story on January 26, 2009, reporting on exactly that kind of breakthrough, New Hope For Restoring Injured Nerves. A group of researchers at the University of Utah uncovered a pathway (a chain of molecular events) involving a gene that, when forced to be overactive, leads to repair of severed nerve cells in nematode worms. The gene is also found in mammalian genomes; thus, the researchers predict they will be able to replicate the study in mammals.

Finding a gene that produces a protein that aids in nerve cell repair in worms is not surprising. Gene theory predicts just that in organisms known to regenerate portions of their anatomy. It also is not necessarily surprising to find the same gene in mammalian systems, since evolutionary theory reveals our common ancestry. What did surprise researchers was that the pathway that results in nerve cell regeneration is not found in developing embryos.

Scientists have puzzled over the fact that nerve cells are regenerated in mammalian embryos and very young, rapidly developing mammals, but not in adults. The question was, what did mammals lose along the way to maturity? The pathway discovered in the new study “is unique in that it is not used by the nervous system during normal embryo development, yet it is absolutely required for regeneration,” one of the researchers said.

How to Turn This News Event into an Inquiry-Based, Standards-Related Science Lesson

Middle school curriculum usually includes some study of cells, genetics, and body systems. This story provides background for some authentic discussions allowing students to apply and extend their knowledge in these three areas. At the same time, it provides opportunity to reinforce concepts in methods of science.

Ask students what happens to a worm that gets cut in half by a gardener’s shovel? To a starfish whose leg is bitten off by a predator? What is regeneration? Have they ever wondered why humans cannot do the same? Do they know that mammalian embryos and very young mammals do have the ability to regenerate? How might regeneration be related to the science of genes? What does the idea of regeneration have to do with curing paralysis in humans?

Remind students of cell theory and show them some visuals of cells, and cells in tissues, organs, and systems. Show them some nerve cells. If they’ve studied the nervous system, they already have some notions regarding nerve cell structure and function. Explain that in paralysis, the nerve is severed and, in adults, not easily repaired.

Point out that scientists have uncovered the worms’ pathway that enables their nerve cells to regenerate. Ask how such a discovery could possibly be useful in mammalian systems? Remind students that all living things share some common characteristics, like cellular structure, DNA, and the ability to respond to stimuli. Is it possible that mammalian genomes could contain the same or similar genes that enable regeneration in worms? As predicted by evolutionary theory, the answer is yes!

So why can’t we regenerate nerve cells? Remind students, or explain, that genes have to be turned on in order to produce the necessary proteins that participate in a pathway culminating in regeneration. In this study, scientists methodically “knocked out” genes, one by one, in worms until they found the one primarily responsible for nerve cell regeneration. (There actually are four genes working together.) When the scientists created conditions that enabled the gene to increase its activity, producing ample protein associated with regeneration, nerve cell regeneration was rapid in adult worms. This confirmed their hypothesis regarding the activity of a particular gene on regeneration. It also enabled them to uncover the steps in the pathway from gene to cell regeneration. Knowing the steps allows scientists to hypothesize possible ways to enhance the pathway in order to induce regeneration in mammals.

Using this story allows you to facilitate student synthesis of knowledge from perhaps three different units in their curriculum around three fundamental theories: cell theory, gene theory and evolutionary theory. It also reinforces concepts associated with the Life Science content standard of the National Science Education Standards, as well as the History and Nature of Science content standard.

Here are additional resources from the National Science Digital Library Middle School Portal 2 (MSP2): Visit Cell City; Middle School Meets Evolution; Cell Differentiation; andCell Biology Animation.

We Want Your Feedback

We want and need your ideas, suggestions, and observations. What would you like to know more about? What questions have your students asked? We invite you to share with us and other readers by posting your comments. Please check back often for our newest posts or download the RSS feed for this blog. Let us know what you think and tell us how we can serve you better. We appreciate your feedback on all of our Middle School Portal 2 publications. You can also email us at msp@msteacher.org.

This post was originally written by Mary LeFever and published January 27, 2009 in the Connecting News to the National Science Education Standards blog. The post was updated 3/22/12 by Jessica Fries-Gaither.

Granite Helps Scientists Piece Together Rodinia

If you’ve taught plate tectonics at the middle school level, you’re probably quite familiar with the supercontinent Pangaea. But did you know that Pangaea was not the only supercontinent in earth’s history – just the last to date? Millions of years before Pangaea, another supercontinent known as Rodinia united all of earth’s landmass in an unusual configuration. While we tend to think of Pangaea as the “starting point,” earth’s land and ocean basins have been continually shaped throughout geologic time through a supercontinent cycle.

While Pangaea certainly gets more press, Rodinia was the star of an article in the July 11, 2008 edition of Science. As summarized in a National Science Foundation News release, John Goodge’s team was collecting geologic specimens in the Transantarctic Mountains when they discovered a single granite boulder atop Nimrod Glacier.

Andrew Barth (L) and Devon Brecke (R), collecting glacial moraine samples in the Miller Range of the Transantarctic Mountains. Photo courtesy of John Goodge, University of Minnesota.

Subsequent chemical and isotopic tests indicated that the boulder was strikingly similar to a belt of igneous rock running through the southwestern United States. These similar chemical and isotopic signatures provided support for the SWEAT (southwest United States East Antarctica) hypothesis, which states that East Antarctica was connected to the southwestern United States approximately one billion years ago, as part of the global supercontinent Rodinia.

The supercontinent Rodinia as it began to break up approximately 750 million years ago.

At the heart of Rodinia was Laurentia, or the precursor to most of North America. Debate exists, however, on whether East Antarctica, Australia, Siberia, or South China fit with the western margin of Laurentia. This geologic discovery provides three lines of evidence in support of an East Antarctica – Laurentia connection.

Researchers theorize that about 600-800 million years ago, a portion of Rodinia broke away, gradually drifting southward to become eastern Antarctica and Australia. This movement just predates the Cambrian explosion, a rapid diversification of life and sudden appearance of complex organisms. Goodge explains that “there are ideas developing about these connections between the geo-tectonic world on the one hand and biology on the other.” It is possible that the shifting and colliding of continents, erosion, and influx of minerals and chemicals into the ocean may have provided nutrients to support a growing diversity of organisms.

Connecting to the National Science Education Standards

As with a discussion of Pangaea or plate tectonics in general, this article provides an opportunity to meet the Earth and Space Science standard’s various concepts. According to the National Science Education Standards, “The idea of systems provides a framework in which students can investigate the four major interacting components of the earth system – geosphere, hydrosphere, atmosphere, and the biosphere. In this holistic approach to studying the planet, physical, chemical, and biological processes act within and among the four components on a wide range of time scales to change continuously earth’s crust, oceans, atmosphere, and living organisms.” The holistic approach described in the NSES is reflected in this study’s use of geologic evidence to explain an important biological phenomenon.

How to Turn This News Event into an Inquiry-Based, Standards-Related Science Lesson

Rather than spark a new lesson, this current event provides an opportunity to revisit a familiar unit on plate tectonics, geologic time, and rocks and minerals. Most teachers include a discussion of Alfred Wegner and the evidence for his theory of plate tectonics, including similar fossilized plants and reptiles found in South America and Africa.

After students understand how Wegner used geologic and fossil evidence to reconstruct Pangaea, present the evidence from this most recent discovery. Ask them to explain how the same type of granite could be found in eastern Antarctica and the southwest United States. Once students conclude that the two continents must have been connected, re-examine a diagram of Pangaea, which shows an African-Antarctic connection, not a North America-Antarctic one. How, then, could these two places have similar rocks?

A reconstruction of the supercontinent Pangaea. Image courtesy of Kieff via Wikimedia.

Referring to geologic time may help at this point. Using a modified time scale, remind students that Pangaea existed approximately 200 million years ago, while earth is approximately 4.6 billion years old. What did earth’s surface look like before Pangaea? Lead students to the conclusion that other supercontinents, like Rodinia, existed well before Pangaea. Introduce the concept of the supercontinent cycle.

This type of discussion naturally progresses to the mechanics and processes driving the cycle: plate movement. The following resources from the Middle School Portal can help you teach about earth’s interior and plate tectonics. It may also be helpful to brush up on concepts related to geologic time, as these processes span millions of years.

Geologic Time: Eons, Eras, and Epochs

Plate Tectonics: Moving Middle School Science

Once students understand plate interactions (rifting, subduction, sea-floor spreading), take a global view. Using a world map, plot the locations of plate divergence and convergence. Challenge students to predict what the next supercontinent will look like. For example, current plate movement indicates that as the Atlantic Ocean basin grows, the Pacific Ocean basin is shrinking. In the future, western North America may be connected to Asia in the earth’s latest supercontinent. This story from NPR, Amasia: The Next Supercontinent?, tells the possible story.

Introducing Rodinia as part of a greater supercontinent cycle presents plate tectonics as a driving force in a long-term pattern of constructive and destructive forces. It provides another opportunity for students to consider the cyclic change: a fundamental principle in science.

We Want Your Feedback
We want and need your ideas, suggestions, and observations. What would you like to know more about? What questions have your students asked? We invite you to share with us and other readers by posting your comments. Please check back often for our newest posts or download the RSS feed for this blog. Let us know what you think and tell us how we can serve you better. We appreciate your feedback on all of our Middle School Portal 2 publications. You can also email us at msp@msteacher.org. This post was originally written by Jessica Fries-Gaither and published July 24, 2008 in the Connecting News to the National Science Education Standards blog. The post was updated 2/8/12 by Jessica Fries-Gaither.

The Origin of Species – 150 Years Young

MY DEAR SIR,—The accompanying papers, which we have the honour of communicating to the Linnean Society, and which all relate to the same subject, viz. the Laws which affect the Production of Varieties, Races, and Species, contain the results of the investigations of two indefatigable naturalists, Mr. Charles Darwin and Mr. Alfred Wallace.

These gentlemen having, independently and unknown to one another, conceived the same very ingenious theory to account for the appearance and perpetuation of varieties and of specific forms on our planet, may both fairly claim the merit of being original thinkers in this important line of inquiry; but neither of them having published his views, though Mr. Darwin has for many years past been repeatedly urged by us to do so, and both authors having now unreservedly placed their papers in our hands, we think it would best promote the interests of science that a selection from them should be laid before the Linnean Society. (from Darwin, C. R. and A. R. Wallace. 1858. On the tendency of species to form varieties; and on the perpetuation of varieties and species by natural means of selection. [Read 1 July] Journal of the Proceedings of the Linnean Society of London. Zoology 3 (20 August): 46-50.)

On July 1st, 1858, papers by Charles Darwin and Alfred Wallace that introduced the theory of evolution by natural selection were read before the Linnean Society of London. The reading of these joint papers was the first public introduction of the theory that was to revolutionize biology, but it was hardly an auspicious occasion. The papers were buried within the reading of several other papers following a long session devoted to general business matters of the Society.

The reading of these papers was hurriedly arranged by Darwin’s friends, Sir Charles Lyell and Dr. J. D. Hooker, in response to Darwin’s shock at having received a letter from Wallace describing the same theory that Darwin had been working on in private for almost 20 years. Upon receiving the letter from Wallace, Darwin rushed to complete his summary so that the two papers could be read together and both scientists would receive credit for the discovery.

Darwin and Wallace did not give eloquent lectures to a cheering mass of Linnean Society members; neither scientist was even present. Wallace was still in Malaysia while Darwin was at home grieving with his wife, Emma, over the death of their 19-month-old son, Charles. Members of the Society were read sections of Darwin and Wallace’s notebooks, papers, and letters. According to Society records, at the end, members walked out not so much stunned by new ideas as overwhelmed by the amount of information loaded upon them.

The importance of the theory of evolution by natural selection was not fully appreciated by the world at large until the release the following year of Darwin’s The Origin of Species, which carefully laid out the argument, backed up by the evidence that elegantly supported the theory.

Over the next 18 months, events such as exhibitions and seminars at London’s Natural History Museum as well as student exchanges and scientific meetings across the world, will culminate in a three day conference in Egypt in November 2009. Let the celebration begin!

References

The Complete Works of Charles Darwin Online

Copies of the original papers presented by Darwin and Wallace at the Linnean Society of London in 1858

The Origin of Species – downloadable version

Darwin Still Causing Waves After 150 Years

How Darwin Won the Evolution Race

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We want and need your ideas, suggestions, and observations. What would you like to know more about? What questions have your students asked? We invite you to share with us and other readers by posting your comments. Please check back often for our newest posts or download the RSS feed for this blog. You can also request email notification when new content is posted (see right navigation bar).

Let us know what you think and tell us how we can serve you better. We want your feedback on all of the NSDL Middle School Portal science publications. Email us at msp@msteacher.org.