Pond Life

Black line represents original
air bubble. Photosynthesis
in the right tube has created an
oxygen bubble.

Test tubes containing pond
water. Tube on the right
received some fertilizer.
 

To study eutrophication I set up a small scale experiment using pond water from the wetlands on the school property. This area is surrounded by athletic fields which are treated with fertilizers. In the spring and summer there is quite the alga bloom and the nasty smell of decaying matter.

One of my colleagues set up a large scale experiment in two little fish bowls, adding fertilizer to one of the bowls. After a week or so there was clearly a difference between the two bowls. The one with the fertilizer was green and becoming greener with each passing day. I did the same except in the test tubes adding a little bit of baking soda to ensure a carbon dioxide source for the growing algae. This piggy backs on my previous post about the Nitrogen cycle. The excess use of fertilizer results in the disruption of the nitrogen cycle and the introduction of excess nitrogen into bodies of water resulting in the overgrowth of algae and the depletion of oxygen in the water causing death among other species in the water. We need to rethink our obsession with thick green lawns and how to obtain them.

It's working...

While Stumbling one day I came across a blog that described growing or should I say Re-growing celeryfrom its stalk. I decided to give it a try. It took some time but the first thing I noticed was the "greening" of the stalks as the exposure to the sunlight and access to water stimulated photosynthesis. Then from the base I began to see the formation of roots which have continued to elongate and multiply. Lastly, from the center is evidence of leaf formation. I have been keeping it on a sunny sill or what can be called a sunny sill as we approach the winter solstice. I'm also making sure to keep it well watered. Eventually I will transfer it to soil and hopefully come spring time put it out in the garden. Since I will be having the students doing an osmosis lab later this week using celery perhaps we will set one of these experiments in the lab to watch the process.

Here you can see the roots forming
at the base of the stalk

Notice the small leaf formation in
the very center.

The Nitrogen cycle

One of the books that I read this summer was Thomas Hager's The Alchemy of Air. This was a fascinating piece of writing mixing science, history and biography in a well woven tale about one of the essential elements of life. Nitrogen is needed for the production of amino and nucleic acids which all living things require. Our planet's atmosphere is 78% nitrogen yet with the rare exception of some bacteria found in soil and cyanobacteria/algae in aquatic ecosystems, living organisms can not use this inert gas directly. Through the activity of nitrogen fixation and the formation of nitric oxide from atmospheric nitrogen and oxygen gases using the energy from lightning to drive the reaction, nitrogen takes on a form that plants and other photosynthetic organisms can absorb and convert into amino and nucleic acids. Nitrogen is returned to the atmosphere by the activity of decomposing bacteria.

 

You're wondering where the book comes in. At the turn of the twentieth century the call went out to find a way to synthesize nitrogen based fertilizers to help feed the growing human population. I bet they never thought we would reach the 7 billion now on the planet, but I digress. The point being that Fritz Haber took up the challenge and designed a way to convert nitrogen and hydrogen gases into ammonia. It took the genius of Carl Bosch to engineer the necessary equipment to make it possible to make ammonia in a profitable large scale way. Today the Haber-Bosch process continues to produce the majority of inorganic fertilizers used in agriculture. According to Hager 50% of the nitrogen in our bodies comes from this process and from the foods we have consumed which have been at one time treated with fertilizers.

 

The problem now is too much nitrogen in the cycle. Excess nitrogen from fertilizers now enters into the soil and water systems. Eutrophication of lakes and the ocean occurs from the over growth of algae which impacts the oxygen levels of the water and kills other aquatic life. Excess nitric oxide in the atmosphere contributes to the formation of acid rain which can lead to pH changes in soil and bodies of water impacting the plants and animals in the affected regions. Too much of a good thing can be a problem.

 

My Ecology class recently did a unit on the geochemical cycles and we discussed the impact of human activity on the nitrogen cycle. The focus has been on the carbon cycle and climate change, that the nitrogen cycle and its disruption often goes unnoticed. The nitrogen cycle's disruption may become part of the next major ecological worries. The background knowledge I gained from this book allowed me to share how science and the development also played a role in the course of history primarily World War II when the Nazi war machine used the technology developed by Haber and Bosch to make synthetic fuel. 

Enzyme Activity Lab

Hydrogen Peroxide and Raw
Potato

A very quick and easy lab to observe enzyme activity is one in which you use raw and cooked potatoes and hydrogen peroxide. Hydrogen peroxide is made as a by-product in cellular processes, it is toxic to cells and that is where the enzyme catalase comes in. The function of catalase is to decompose hydrogen peroxide into water and oxygen gas. You've observed this if you've ever used hydrogen peroxide to disinfect a cut or scrape. Students can observe the activity of the catalase by looking for the bubbles of oxygen that are released.

Enzymes which are a class of proteins are subject to the threat of denaturation, or the loss of their 3-D structure, when exposed to changes in pH or heat. In this lab I have the students mix in some vinegar into the hydrogen peroxide to lower the pH of the environment. As a result there is a visible slowing down of the reaction. We also use a baking soda solution to create an alkaline environment but the enzyme isn't impacted as much. Lastly, I have them test a piece of cooked potato. In the cooking process the catalase is denatured and there is no activity at all.

Hydrogen peroxide and
cooked potato

We have been investing in Vernier Lab Quest equipment for student data collection. Using a very crude methodology, I had the students stopper up the test tubes and use the Gas Pressure Sensor to observe any pressure changes that result from the release of the oxygen from the decomposition reaction. It worked. Clearly there was a significant pressure change with the raw potato and hydrogen peroxide, less change with the vinegar mixed in, and absolutely no change in pressure when the cooked potato was tested. Vernier does put out a series of experimental procedures that are more sophisticated and quantifiable. In this case I was focused on the students learning the key concepts of enzymes (active site, activation energy, catalyst) and the conditions that will lead to protein denaturation.

Testing for pressure change using a Vernier Lab Quest
with a Gas Pressure Sensor.

Concept mapping

In the never ending quest to assist students (high school sophomores in a college prep biology class) in learning new and difficult material, like macromolecules for example, my colleague and I developed a list of key terms for the students to map. Concept maps can take several different forms such as a top down flow chart or a web. Here I show just one portion of a larger map. As we moved through the unit I would have the students take their maps out and add new details to them. Tomorrow is the big unit test, they will be allowed to use the map on the test and turn it in for a classwork grade. Keep your fingers crossed for good results. The biggest challenge will be can they retain it as we move on in our curriculum and succeed on the mid-year exams?

Concept Map featuring terms about Lipids, includes key terms, examples, functions, etc.

Testing for starch

We continue with our unit about macromolecules and turn our focus on carbohydrates. All carbohydrates are formed from simple sugar monomers also called monosaccharides, examples include glucose, fructose, and galactose. Through the process of dehydration synthesis two monosaccharides become a disaccharide like sucrose made of one glucose and one fructose molecule. Start stinging more together and you get polysaccharides such as glycogen made by animals for glucose storage, cellulose by plants as a building material for sturdy cell walls (think the crunchiness of celery), and lastly starch also produced by plants for glucose storage and eaten by animals (including us) for energy (got to love those mashed potatoes).

Starch will react with an iodine solution to turn black. The iodine will react with the coil structure of starch but not with simple sugars or even carbohydrate food sources high in fiber. In the photo below you can see a sample of carbohydrates that we tested for the presence of starch. As a control I have the students start with a known sample of corn starch. Test items included: white potato, wheat bread, saltine cracker, apple, banana, table sugar, white flour, celery, lettuce, Chinese yam, macaroni, flaxseed meal, and a piece of notebook paper. Note that we give the students a wax coated paper plate to work on. Can you guess why? That's one of the post lab questions.

Macromolecules the "Legos" of life

The most challenging of all chapters in biology I think for sophomore level high school students is the one on the biochemistry of life. I try all types of techniques to help them with this subject matter. One thing is to use the molecule building kits to make the material presented on the 2-dimensional textbook page become a 3-dimensional reality. I remind them that they are made up of millions if not billions of these molecules and they are not flat structures themselves. Yesterday we built functional groups: hydroxyl, carbonyl, carboxyl, and amine. Then I had them put some of them together to build the simplest of all amino acids - alanine as pictured below. One of the biggest challenges is to convince them it is time to stop playing and clean up. Don't leave any atoms or bonds on the floor.

Water, water everywhere

In Biology class we are currently in our unit on the chemistry of life. This week our focus was on water chemistry, its properties, solutions, and The pH scale. We explored the properties of adhesion, cohesion, density and capillary action by carrying out several demonstrations based on the Project WET curriculum. It was amazing to hear the students' responses to some of the activities. One young man who was playing with a large drop of water on wax paper exclaimed, "why have I never done this before!" Many were fascinated with what happened when I slipped a sheet of print under the wax paper and it was magnified. Amazing what the property of cohesion can do. Hopefully seeing water in action will help them to remember the key terms and relate them to the role water plays in life on our planet.

Lions, tigers, and bears oh my - food webs

Producers, consumers, and decomposers too. Today in Ecology class I gave groups of students an envelope containing the names of various organisms and their feeding patterns. Their task was to organize a food web based on these organisms. Here is an example of one of the webs that was generated. Tomorrow we will discuss keystone organisms, energy pyramids, and biological magnification.

Soda can calorimeter by Flinn

In chemistry yesterday we set up the Soda can calorimeter experiment.  I found this set up a bit better than using a wire mesh sitting on top of the ring clamp. More heat was transferred to the can that way. The other modification that my colleague and I made was to use a watch glass and a large paper clip to put the food sample on for burning. The students really enjoyed the lab. I think everyone was fascinated to watch the cheeseballs go up in flames. The really do burn well compared to the marshmallows. Hopefully they will make the connection between the calories they consume and the unit of energy. The other nice thing about Flinn's write up is their easy to follow calculations set out step by step.

Particulate matter pollution

The ecology class took a look at pollution recently when we set out some PM (particulate matter) pollution detectors. Granted the EPA defines PM particles as between the range of 0-10 micrometers and what we captured is much larger but it gave us all an idea of the debris that is falling from the sky or being generated from the ground when disturbed by activity. So many of our students suffer from asthma that it is good to raise their awareness, and everyone else, of one of the many sources that can trigger an attack.

The detectors were made using a petri dish, a wax pencil to make a circle the size of a quarter, then a thin layer of petroleum jelly spread in the circle. We placed the detectors out for 48 hours and retrieved them. Unfortunately we had a rainstorm in between. I feared that would ruin our results but there was matter stuck in the petroleum jelly anyways. This is why you can see water droplets in the photos below. Under the dissecting scope (40x magnification) we could observe: dirt particles, pollen grains, tiny insects, and other debris. 

This detector was on the ground below an air exchange unit that is above on the roof.

Three of our detectors

Food for thought

In ecology class we have been discussing the human footprint and population growth. We watched National Geographic's Human Footprint which takes the viewer through the life of two individuals from birth to old age showing the lifetime amount of everyday items they consume (diapers, eggs, bananas, clothing, appliances, and the list goes on) and the amount of waste generated. This is an eye opener when you see all the cartons of milk you might drink in a lifetime all lined up.

This led us to looking at the wealth of the various regions of the world. I found the Food for thought activity in my researches. After some discussion of the material in our text, I divided up the class according to the instructions. One challenge was to calculate the percentages based on the number of students I actually have in class plus the use of empty chairs for a few of the absent students. We followed the discussion questions and it was very interesting to watch the students' reactions when I began to pass out the match sticks. Follow that up with the presentation of the chocolate kisses. When I asked "Asia" and "Africa" how they felt about "North America" and "Europe's" wealth, one student replied that she was "pissed" (American slang here for angry and not British slang).  That got the class talking.

One student remarked as she was leaving the classroom, "best class ever - movie and chocolate all in one period." I hope the lesson wasn't lost on her.

Need help with a lesson?

I've found a most helpful website in Teacher's Domain sponsored by Public broadcasting "and viewers like you." There you will find video clips, documents, interactive activities, lesson plans, and a whole lot more. What's nice to know is that even college professors are using this site as I experienced this summer while taking a very well thought out and organized online course offered by Fitchburg State University. I've been able to supplement my power point lectures with content rich video clips which are 3-5 minutes in length on average, and can serve as great conversation generators. I'm so glad to know that my annual membership to WGBH is going to serve a good cause namely me and my fellow teachers in the classroom. Not to mention the benefits to our students!