Measurement and observation
Marin Headlands: photograph of Marin Headlands from the Golden Gate Bridge by Christopher BelandSummary
The Marin Headlands contain the geologic record of a great deal of plate tectonic action that can be used to piece together the history of the formation of California. Briefly, around 180 million year ago, the North American plate collided with a now subducted plate called the Farallon plate. As the Farallon plate dove under the North American plate, bits and pieces of the Farallon plate were scraped off. These bits and pieces can be found in the Marin Headlands in several distinctive rock formations: pillow basalts (at the Point Bonita Lighthouse), chert (near Rodeo Lagoon), and sandstone (at Rodeo Beach). By closely observing these rocks and figuring out how they formed, an understanding of how California itself was formed may be inferred.
Raising trout from eggs to fry in the classroom is a fabulous way for students to observe and study the life cycle of vertebrates and simultaneously learn about threatened species in local watersheds. Many states have programs where teachers and students raise trout in their classrooms in partnership with the Department of Fish and Wildlife for later release into a designated lake, creek or river. Described here is information for teachers on how to partner with state agencies, fish hatcheries, and local fly-fisher groups to raise rainbow trout in the classroom. A worksheet for the trout release field trip is provided. Best of all, many Trout in the Classroom Programs are fully supported by local fly-fisher groups and the California Department of Fish and Game (such as the California program that I participated in), and thus there is no materials cost to the teacher beyond the costs of organizing the trout release field trip at the end of the project.
To study the life cycle and structure of plants, students grow plants from seed, fertilize them, and collect seed, starting the process over again. With the right growing conditions, almost any plant can be grown successfully in the classroom – native plants for a restoration project, vegetables, cut flowers, etc. The instructions provided here are for growing Wisconsin Fast Plants since they are the most widely used species in classrooms across America. These plants have been artificially selected to grow well in small spaces, with indoor lighting, with little soil, and with an exceedingly short life cycle (14-20 days to flower and 21-40 days to set seed). Therefore, they are incredibly well adapted to survive in classroom conditions as well as participate in multi-generational studies such as plant life cycle studies, Mendelian crosses and artificial trait selection. However, the light boxes and terraqua columns lend themselves to growing virtually any
- Frogs (order them from Carolina Biological catalog # 22-7444, 22-7445, 22-7446, 22-7464, 22-7465, 22-7466, between $3.35 - $5.95 depending on the quantity ordered and whether there is any color injection)
- Paper plate or dissection tray
- Scalpel or razor blade
- Optional: dissection probes
- Optional: dissection pins (especially useful if you have dissection trays on which to use them)
- Flowers, possibly of several different species for cross-species comparisons. Almost any flower may be used although the anatomy is more easily distinguished in some flowers than others. Some common flowers with clearly differentiated parts include:Sarracenia flower dissection: Image courtexy of Noah Elhardt
- Wisconsin fast plant
- Paper plates/plastic trays
- Scissors or razor blade (to open the ovary)
- Hand lens
- Optional: tweezers
- Optional: dissecting scope
|Sarracenia flower dissection: Image courtexy of Noah Elhardt
||Leopard frog in duckweed: Image courtesy of Steven Dunlop
To learn about the structure and function of living things, it is essential to explore the anatomy of real organisms up close and personal. While much can be accomplished by studying living things and their life cycles (see Raising Plants and Raising Trout projects), dissections offer a view of the internal structures and how they contribute to the whole. What follows are resources and information for teachers interested in conducting a flower and/or frog dissection. There are many excellent lesson plans and dissection guides on the web already. Rather than recreate these resources here, My Science Box provides nitty-gritty logistics and resources such as a selected list of great web resources, how to order frogs, what equipment you need, student handouts, and teaching strategies.
Sail aboard a research vessel and explore the living treasures of the San Francisco Bay. The Marine Science Institute (MSI) provides some of the best hands-on science and environmental education in the Bay Area. On the Discovery Voyage, students spend 4 hours learning about the San Francisco Bay ecosystem by examining water quality and collecting organisms at every level of the food web from microscopic plankton to mud dwellers to bat rays and fish. The diversity of life in the Bay is astounding and surprising to students who have spent their whole lives living by its water but never “diving in”. If a half-day voyage isn’t for you, many other fantastic programs are available including Inland Voyages (where live marine organisms come to you), Ocean Lab (where students explore animals of the rocky coastal ecosystem in MSI’s Discovery Lab classrooms), and Tidepool Expeditions (where MSI naturalists provide a guided tour of the tidepool creatures at Pillar Point).
Bubbling Yeast: Thanks to Ellen Loehman for creating this image.Yeast are a single celled fungi that are a great model organism for studying respiration in the classroom. The species Saccharomyces cerevisiae is commonly used for leavening bread and fermenting beer but other species such as Candida albicans are known to cause infections in humans (vaginal yeast infections and diaper rash being the most common). In this investigation, students fill the bulb of a disposable pipet (eyedropper) with yeast, then submerge the pipet in a test tube of water. They can then measure the rate of respiration by counting the number of bubbles of carbon dioxide gas that emerge from the tip of the pipet in a certain length of time. By varying the temperature and the nutrient source, students can discover what variables affect the rate of respiration in yeast. By submerging the pipet in bromthymol blue (see Colorful Respiration activity), students can identify the gas being produced as carbon dioxide.
Blow through a straw into bluish liquid and watch it turn green then yellow before your eyes. Put some plants into the yellow liquid, leave it in a sunny window, come back the next day and the liquid is green. What if you leave the plants in the dark? What if you put some pond snails in? What if you put both pond snails and plants? What’s going on?
The liquid is bromthymol blue (BTB) a non-toxic acid-base indicator that can be used to indirectly measure levels of dissolved carbon dioxide (CO2). The amount of CO2 in a solution changes the pH. An increase in CO2 makes a solution more acidic (the pH gets lower). A decrease in CO2 makes a solution more basic (the pH gets higher). The reason for this is that carbon dioxide that is dissolved in water is in equilibrium with carbonic acid (H2CO3).
CO2 + H2O ↔ H2CO3
In any solution, while the majority of CO2 stays as CO2, some of it is converted to H2CO3, turning the solution slightly acidic. If CO2 is added to the water, the level of H2CO3 will rise and the solution will become more acidic. If CO2 is removed from the water, the amount of H2CO3 falls and the solution becomes more basic. Thus, acid-base indicators such as BTB can indirectly measure the amount of CO2 in a solution.
For more than you ever wanted to know about carbonic acid, see the Wikipedia article on carbonic acid. For the example lesson plans developed by Bob Culler through Access Excellence at the National Health Museum. For a great time lapse video showing BTB color changes using elodea and snails, see Activity C13 from Addison-Wesley’s Science 10 curriculum.
- Bromthymol blue (BTB can be ordered from any science supply company such as Flinn Scientific $9 for 1 liter 0.04% BTB solution).
- Several 2 liter soda bottles
- Test tubes
- 500 ml beakers or disposable plastic or paper cups
- Water (since the pH of tap water varies, you may wish to use distilled water for your master BTB solution)
- Drinking straws
- Plastic wrap
- Pond snails
- Before the lesson, the teacher should mix a master BTB solution in one or more 2 liter soda bottles. For each 2 liter bottle, mix 120 ml 0.04% BTB with 1800 ml water. The end result should be a medium blue master BTB solution, dilute enough to be safe for plants and snails but dark enough to see the color changes.
- Pour 200 ml diluted BTB in a beaker or cup.
- Take a deep breath then blow bubbles in the BTB solution through a drinking straw. What happened? Why?
- Set up a test tube rack with 3 tubes. In tube #1 put unbubbled BTB solution (blue). In tube #2 put bubbled BTB solution (yellow). Tubes #1 and #2 will be your comparison tubes. In tube #3 you have a choice of what to do. Choose one option from each of the following columns:
|bubbled BTB (yellow)
||spring of Elodea
||Sunny window/bright light
|unbubbled BTB (blue)
||5 pond snails
||Dark closet/drak heavy cloth
||both Elodea and 5 pond snails
- Make a hypothesis about what will happen to your tube.
- After 24 hours, check the color of your tube. What happened? Why?
These experiments use a bell jar (or any other very large, clear, glass jar) to determine the identity of the gas produced by plants. It mirrors the famous experiments of Joseph Priestley and Jan Ingenhousz from the 1700’s that first demonstrated the existence of oxygen and its importance to plants and animals.
In 1771 and 1772, Priestly conducted a series of experiments using a bell jar. It was known that a candle placed in a sealed bell jar would eventually burn out and could not be relighted while still in the jar. Priestly discovered that a plant can survive indefinitely within a jar. Thus, he tried placing a plant into the jar with the burning candle. The candle went out as before and could not be relit right away. Priestly waited several days and tried again. The candle could be relit! The plant had restored the air inside the jar! (Do not try the next series of experiments since it harms animals!) Next priestly investigated what would happen to animals. He found that a mouse placed inside a sealed jar will eventually collapse. However, a mouse can survive in a sealed jar with a plant since the plant restores the air. Priestly was the first to demonstrate that oxygen is necessary for fire and animals but that given time, plants can create oxygen, allowing fires to burn and animals to breathe.