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Unfortunately, students in an urban setting rarely have meaningful experiences with nature. In many cases, they lack the opportunities to develop and explore curiosities about their natural environment. In turn, they also lack the understanding of the interdependencies of humans, other species, and the physical environment, and therefore lack the knowledge necessary to be stewards of the watershed in which they live. Richmond, Virginia provides the ideal setting for students to gain "meaningful watershed experiences." The James River runs directly through downtown Richmond, and eventually empties into the Chesapeake Bay, which has been classified as an impaired water body, with repeated monitored violations of water quality criteria.
This curriculum unit is designed to accomplish two goals. The first is to increase students' awareness of the impact of their daily choices on the James River and Chesapeake Bay watershed. The second is to introduce research and inquiry-based practices in the classroom and in the field to encourage questioning and experimentation, thus promoting more holistic learning of science concepts.
I teach 7th grade Life Science at a middle school that mostly serves low-income neighborhoods. Despite the fact that the James River is less than five miles away and very accessible to the public thanks to the James River Park System, many of my students rarely, if ever, have the opportunity to visit the river. The standards of learning adopted in Virginia require that students "understand the natural processes and human interactions that affect watershed systems" in 6th grade, therefore this unit will allow students to apply their knowledge to learn more about the living aspects of the ecosystem. However, students at my school do not have the opportunity in 6th grade to visit the river and see first-hand what they are learning in the classroom. Therefore, it is important to begin the year with a field trip to the river, in which students use hand-held field equipment to assess the health of the watershed.
Being mainly from low-income households, many of my students may not be aware of the many different roles scientists play in our society. Most are familiar with the more common science careers, such as doctors or veterinarians, but may not realize how integral scientists have been in efforts to preserve the health of our environment and thus our lives. Throughout this curriculum unit, I will introduce students to various professionals who are or have been involved in conservation or research related to the Chesapeake Bay watershed, with the hopes that it will expand their horizons and give them a broader view of the potential opportunities in science or science-related fields.
Another general characteristic of my student population is they are not accustomed to open-ended questioning and experimentation in the classroom. Because of the current climate of school accountability, the focus has shifted in many urban schools to standardized test preparation. Despite the fact that many of the questions on the standardized tests require students to be familiar with field equipment and to use critical thinking skills, many of them do not have the necessary background and experience to be successful. I want to begin the year by introducing structured and guided inquiry related to human impact on the watershed, with the goal that students will develop the skills to later conduct independent open inquiry in the form of science-fair projects.
Inquiry-based Learning: Why?
A common misconception in science classrooms is that science is meant to be a large body of facts, however the scientific process of asking questions and testing hypotheses through experimentation is an important skill that should be emphasized from very early in a child's education. The science education community is aware of this problem, recognizing that inquiry practices are important not only for engaging students who may otherwise be difficult to engage, but also to encourage students to develop a deeper understanding of the world around them. The excitement of discovery and "doing" science can also make science accessible and interesting to the most reluctant students. Inquiry practices are student-centered and require that the student is actively participating in the learning process rather than more traditional teacher-centered practices that require the student to passively absorb a series of facts and definitions. The National Academy of Sciences Framework for K-12 Science Education emphasizes that the following practices are essential to effective science education 1:
- Asking questions (for science) and defining problems (for engineering)
- Developing and using models
- Planning and carrying out investigations
- Analyzing and interpreting data
- Using mathematics and computational thinking
- Constructing explanations (for science) and designing solutions (for
- Engaging in argument from evidence
- Obtaining, evaluating, and communicating information
Types of Inquiry
As mentioned above, if students do not have sufficient experience with the scientific process, the teacher must scaffold and guide students in order to ensure that students have positive, successful experiences in the science classroom. Traditionally, many teachers have used what are sometimes called "cookbook labs" in which the expected outcome is known prior to the activity and there is a "right answer." Some teachers are even apprehensive about doing these types of straightforward labs because of potential behavior issues and difficulty keeping students focused. "Cookbook labs" can be useful for teaching some concepts, but are not necessarily student-centered and usually do not promote questioning and experimentation.
Structured inquiry is the next step toward open inquiry, in which the teacher gives the students a suggested procedure and materials, but the expected outcome is unknown. Structured inquiry is essential to introduce inquiry practices to students who are not accustomed to this way of thinking, and encourages students to form hypotheses and ask further questions about how or why they obtained the results they did. The next step is guided inquiry, in which the student is responsible for developing the procedure. Finally, in open inquiry, students define their own problem or question, develop a procedure, and interpret and communicate the results 2.
The activities included in this curriculum unit are designed specifically to integrate all of the inquiry practices suggested by the National Academy of Sciences by gradually building skills from the level of structured inquiry to the level of open inquiry, thus developing the problem solving and critical thinking skills that will be useful to students not only in science class, but also for their lives. And, by focusing on the James River and Chesapeake Bay, in their own backyard, the work the students do will be relevant and meaningful to them, allowing them to take ownership of their experience and knowledge.
The Water Cycle and Pollution
Students will first review the terminology and concepts related to the global water cycle, including evaporation, condensation, precipitation, runoff, and accumulation, first using a physical model, then an online water cycle module at the ITSI-SU website (http://itsisu.portal.concord.org/). The module includes a model that allows the students to change ocean temperature and wind direction and speed, to see how these changes affect how water moves through the environment. This knowledge will be applied to predict how pollutants that are dissolved in the water or present in the air may be moved through the environment in the same way, especially through runoff.
One type of point source pollution that is moved through the environment by the water cycle is acid rain. Acid rain is the result of sulfuric and nitric acid formed by reactions of water and oxygen in the atmosphere, with sulfur dioxide and nitrogen oxides emitted from the burning of fossil fuels. The acidic compounds can move through the atmosphere through water vapor in the air, precipitation, and runoff 3.
Question: How does acid rain affect living things?
Using structured inquiry, students will have the opportunity to test how acid rain affects plant germination and growth. Groups of students will use Bottle Biology (http://www.bottlebiology.org/) to grow radish plants with neutral and acidic water. Radishes grow quickly and easily. The teacher will provide the procedure, and students will gain practice forming hypotheses, evaluating data, and making conclusions.
The most common form of pollution that is carried through the environment by the water cycle is from agricultural runoff, a nonpoint source of pollution. Nitrogen and phosphorus used to fertilize crops and lawns is carried through runoff into bodies of water. Because nitrogen and phosphorus stimulate the growth of both plants and algae, in excess they cause algal blooms in streams, rivers, ponds, and lakes, which deplete the oxygen in the water (called eutrophication) and hinders the survival of other species, such as fish and invertebrates. In extreme cases, eutrophication can cause large areas called "dead zones" at the mouths of rivers, such as at the mouth of the Mississippi River in the Gulf of Mexico. Excess nitrates in drinking water can also cause methemoglobinemia, or blue baby syndrome, which can kill infants. Another component of agricultural runoff is sediment that is carried from crop fields, and can cloud the water, preventing sunlight from reaching aquatic plants. Sediment can also carry other pollutants, such as pesticides or herbicides, which are attached to soil particles 4.
Many methods have been suggested and implemented to prevent an excess of nutrients and sediment from reaching bodies of water. If farmers test the soil and apply only the amount of fertilizer that is needed, most of the nitrogen and phosphorus will be taken up by the plants. Farmers can also plant buffer zones of plants, such as grasses, at the edge of crop fields to take up the nitrogen and phosphorus as the water runs off the field 5.
Question: How is the James River in Richmond, Virginia affected by nonpoint sources of pollution, such as agricultural or urban runoff?
Despite regulations, nonpoint sources of pollution, such as nutrient and sediment runoff, are most commonly responsible for impairment of water bodies. Students will make predictions about what types of pollutants might be common in the school neighborhood. Using structured inquiry in order to test the levels of these pollutants in the James River, students will be given procedures for using hand-held field equipment along with a LaMotte water quality testing kit to determine pH (which can be correlated to the previous investigation into the effects of acid rain), dissolved oxygen, nitrate and phosphate levels, and turbidity. Students will then use the data to assess the health of the river, and predict how the animals and plants in the river may be affected by the water quality. Students will also participate in a larger project by entering data into an international database of water quality for the World Water Monitoring Challenge (http://www.wwmd.org).
Life in the Chesapeake Bay Watershed
The James River originates in Western Virginia and flows 340 miles across the state, finally emptying into the Chesapeake Bay, creating an estuary that is spawning ground for many species of fish, home to oyster beds, and prime habitat for birds on their migratory routes. Historically and currently, the river is also used by humans for recreation, fishing, and industry.
The James River hasn't always been in a condition suitable for recreation and fishing. Before legislation that regulated the discharge that is released into the river, toxic chemicals and sewage were emptied into the river by industries with the notion that "the solution to pollution is dilution." Unfortunately, the pollution killed most life in the river in the 1950s. Because of regulations, the river has improved, and supports many species of fish, aquatic invertebrates, and plants. The primary concerns today are nutrient and sediment overload from agricultural and urban runoff leading to eutrophication, and invasive species 6.
In Richmond, the fall line separates the freshwater, fast-flowing rocky upper and middle sections of the James River from the tidal, brackish water of the lower James River. For this curriculum unit, the focus will be on life in the estuary, which includes the lower James River and the Chesapeake Bay. Many species that were common prior to colonization have since been negatively impacted by human activity.
American shad (Alosa sapidissima) are anadramous, meaning that they live as adults in saltwater, and swim upriver to breed and spawn in freshwater. Shad swim up the James River to spawn in the spring, and juvenile shad spend the summer in freshwater before returning to the ocean in the fall. They grow and develop in the ocean for three to six years, after which they swim back up the river to spawn. Juveniles eat zooplankton and terrestrial insects, and adults eat plankton, crustaceans, and small fish. They can live up to 11 years. Before colonization shad were common in the James River and the Chesapeake Bay. By the late 1800s, shad populations began to decline due to overharvesting, pollution, and dams that blocked the spawning route. Shad fishing is now banned in an effort to allow the populations to recover. Recent restoration efforts, including reintroduction of captive-bred shad, building fish ladders to help them get over dams, and removing other barriers to spawning, have slightly increased the numbers of shad, but the population is still suffering 7.
The Atlantic Sturgeon (Acipenser oxyrinchus) is also an anadromous fish, but is even rarer than shad. Atlantic sturgeon females spawn at 18 to 20 years old, and weigh more than 100 pounds 8. Before colonization, a rite of passage for young Native American boys was to grab the gills of a large adult sturgeon and ride it up the river. Sturgeons are bottom-feeders, eating snails, crustaceans, shellfish, and small fish. Sturgeon were valued by humans as food, especially their eggs, or roe, which were in especially high demand in Europe in the 1800s8 , 9. By the early 1900s, the population of sturgeon was almost completely wiped out. Now they are rarely seen in the James River. It is illegal to harvest them, however they are occasionally caught accidentally in nets. Besides overharvesting, there is a lack of forest litter at the bottom of rivers for sturgeon to attach their eggs to, mainly due to deforestation and development along rivers. Eutrophication caused by excess nutrient load from agricultural and urban runoff also limits oxygen levels in areas where eggs and juveniles develop. Restoration efforts, including releasing hatchery-raised fish, have had limited success8 .
Rockfish (also called Striped Bass)
Rockfish (Morone saxatilis) are also anadromous, and their range extends from Canada to Florida in the Atlantic Ocean. Juveniles develop in freshwater for about three years, then migrate back to the ocean. They begin spawning at five to seven years old, and can live up to 30 years. They eat shellfish, eels, bloodworms and small fish, including herring, juvenile shad, and mackerel. They are a prized game fish, and were also harvested commercially since colonization. In the 1970s, the population of rockfish declined dramatically. As with other fish in the Chesapeake Bay, the decline was due to overharvesting and water quality issues, including temperature fluctuations and pollution of spawning areas. The Chesapeake Bay is the primary nursery area for 70-90% of rockfish. Scientists have researched the reason for their decline and began tagging fish to determine causes of mortality. Tagged hatchery-reared fish have been reintroduced and tracked to determine the success of reintroduction programs. The rockfish population has begun to bounce back, and continues to increase8 .
Atlantic menhaden (Brevoortia tyrannus) are a commercially important fish, being a good source of omega-3-fatty acids. Fish meal and crude fish oil made from menhaden are used commonly in aquaculture of other fish, and refined fish oil is used as dietary supplements for people. Menhaden are filter feeders on phytoplankton and zooplankton, thus helping filter bay water. They are also an important food source for larger fish and predatory birds such as osprey and eagles. Menhaden fisheries are selective and efficient, with very limited by-catch. They can live up to 12 years, and spend their entire lives in the bay. Interestingly, menhaden were used as crop fertilizer by Native Americans and pre-colonial Americans8 .
Blue crabs (Callinectes sapidus) are known for being excellent swimmers, unlike most species of crabs. They are found throughout the Atlantic Coast. Blue crabs are bottom-feeders, and feed on fish, other crabs, clams, sea lettuce, eelgrass, and decaying vegetation. Submerged aquatic vegetation (see below) is especially important to protect juvenile crabs from predators during molting. Blue crabs can live up to about three years, and reach maturity after one year. Predators include larger fish, herons, turtles, and humans. Blue crabs are abundant and commonly harvested; however, size and harvest limits are in place to protect them from overharvesting8 .
American eels (Anguilla rostrata) live in shallow water and are common throughout the Chesapeake Bay. They are nocturnal and eat small fish, shellfish, and soft-shelled crabs. They are prey to gulls, eagles, and ospreys. Eels are catadromous, meaning they live in freshwater and spawn in the ocean. After they spawn in the Sargasso Sea, south of the Bahamas, they die. They live about five years. Unlike the anadromous fish, they are very good at getting past blockages in the river because of their shape. American eels are not widely harvested, but are considered a delicacy in Asia and Europe8 .
Perhaps one of the most significant and detrimental effects of humans on the Chesapeake Bay watershed is the decimation of the eastern oyster population. By the early 1800s, oyster populations in the New England region began to decline from overfishing, therefore settlers turned their attention to Virginia. They began exploiting the Chesapeake Bay using damaging dredging techniques, which were subsequently banned in 1811. However, later, deepwater dredging was permitted because of the high demand for oysters, not just as food, but also the shells were used by farmers as fertilizer and chicken grit. Annual oyster harvests declined from 17 million bushels in the late 1800s to less than 100,000 in more recent years not only because there are fewer oysters, but also less suitable habitat available for oysters to colonize due to the damaging effects of dredging6 .
In addition to overharvesting and habitat destruction, oysters have more recently been suffering from two major diseases caused by protozoan parasites, MSX disease and Dermo disease, both being more common in waters with higher salinity, specifically in the estuary in Virginia. Oysters in the northern part of the bay in Maryland are less susceptible to disease. The spreading of disease is one of the accidental drawbacks to restoration efforts, as aquaculturists may have unknowingly reintroduced many diseased oysters into the bay.
The most important contribution of oysters to the health of the Chesapeake Bay is to filter harmful chemicals from the water. The Chesapeake Bay is estimated to hold 19 billion gallons of water. A single oyster can filter up to 50 gallons a day, therefore at the time of oyster abundance, the entire bay could be filtered every week. With the current population, it would take a year to filter the bay. Because of the increased nutrient and sediment runoff from the James River and other tributaries, filtration by oysters is more valuable than ever6 , 8 .
Oysters are not only important for filtration, but they also provide substrate and shelter for many other Chesapeake Bay species, including mussels, barnacles, and fish. Oyster reefs were historically vertical, which not only created more nooks and crannies for fish to hide in, but also effectively circulated and oxygenated the water, making the water more suitable for other species. More recently, due to damage to the substrate by oyster dredging, oyster beds are flat, which limits the number of oysters that can utilize the available space, and does not provide nearly as much shelter for other species. In addition, because oysters filter floating phytoplankton from the water, the decline in oysters has led to a shift in the food web from domination by bottom-dwelling organisms, to more free-floating zooplankton and larger organisms such as sea nettles (a type of jellyfish) that feed on zooplankton. It has been suggested that the decline in oysters may have played a direct role in the increase in stinging sea nettles, thus impacting fishing and recreation in the bay6 .
Scientists and government officials have been integral in understanding oyster ecology and disease and spreading awareness of the importance of oysters to the health of the Chesapeake Bay. Scientists have developed a molecular probe to detect disease before it infects an oyster grower's entire stock. Another effort has focused on breeding disease-resistant strains of oysters that can be introduced in large numbers into the bay.
A local professor at Virginia Commonwealth University (VCU), Dr. Bonnie Brown, and her doctoral student, Colleen Higgins, have been working to quantify the amount of nutrient load that can be removed from the water using farmed oysters with the goal of promoting incentives for oyster farming in the Chesapeake Bay region. A video made by VCU about Dr. Brown's oyster farming, along with her other conservation efforts will be shown in the classroom to reinforce the idea that people's daily choices can have a larger impact on the environment. The video can be found at http://www.vcutvhd.vcu.edu/shows/insideout/bonnie.html.
Question: How are we connected to the Chesapeake Bay?
Students will use a map to determine the distance of the school from the James River and the Chesapeake Bay, and the path that water that runs off from the school grounds would take to reach the bay1 0 . Students will also predict what types of pollutants may flow into the watershed from their school or home, and how they may affect living things in the river and the bay.
Question: What types of animals are common in the tidal portion of the James River and the Chesapeake Bay? How do they positively or negatively affect the estuarine ecosystem?
Many populations of aquatic species have declined due to human impact, and it is to be expected that a shift in abundance and distribution would have some impact on the estuarine ecosystem. In order to understand specifically how the ecosystem is impacted, students will research, using print and internet sources, seven previously common native river and bay species, including oysters, crabs, menhaden, shad, sturgeon, rockfish, and eels. Students will work cooperatively in groups to research the basic needs and habitat of their assigned species. As an introduction to open inquiry, students will form questions that can be used to evaluate the "value" of their species to the ecosystem and to humans. Examples of questions might be: "What characteristics of the species are most beneficial to the ecosystem?", and "What characteristics of the species make them beneficial or desirable to humans?" Students will then use critical thinking skills to weigh the relative importance of these characteristics. Each group will then communicate their analyses by developing a creative way of describing the "talents" of their species using a song, rap, poem, or skit. One student from each group will then vote on "Best Bay Critter," or the species that is most valuable to both the ecosystem and humans. Also, students as a class will evaluate the information communicated by each group to declare a "Best Bay Critter 1 0."
Question: Can we design a filter that will clean the water as quickly and effectively as oysters?
Students will use a guided inquiry activity to answer this question. First, students will observe oysters filtering algae or silt that are added to tanks of water. Then students will try to design a filter that can filter as quickly as oysters using various household materials. The students will test their designed filters, then have a chance to redesign the filters and retest them1 0 . This activity gives the students the opportunity to design their own procedure and predictions, and to independently assess the effectiveness of their design, which addresses several of the inquiry practices recommended by the National Academy of Sciences (see above).
Submerged Aquatic Vegetation
Submerged aquatic vegetation (SAV) in the Chesapeake Bay and tidal region of the James River is extremely important to the health of the bay ecosystem. Some of the species of SAV include Eurasian watermilfoil, redhead grass, Sago pondweed, eelgrass, wild celery, horned pondweed, waterweed, and bushy pondweed, and muskgrass, which is actually an alga. Most plants cannot tolerate the salinity of the estuary, but these species have adapted by secreting excess salt from their leaves. These grasses are the foundation of the Chesapeake Bay food web, providing food and habitat for blue crabs, juvenile fish, and many species of waterfowl6 , 8 .
SAV is often used as an indicator of water quality, as these plants depend on clear water in order to obtain enough light to survive. SAV decreases the velocity of water flow, allowing sediment to settle to the bottom, therefore if the amount of SAV is decreased significantly due to other factors, increased suspended sediment can inhibit the growth of the remaining SAV. In addition to decreasing suspended sediment, grasses take up nitrogen and phosphorus that are common in agricultural and urban runoff, thus helping to prevent the growth of excess algae6 , 8 .
Unfortunately, the abundance of bay grasses has decreased dramatically since the early 1970s. Hurricane Agnes in 1972 may have damaged the grass population by increasing sediment and decreasing salinity, however grasses have previously been able to recover from even more damaging storms. SAV may not have been able to bounce back after Agnes because of the many other stressors affecting their growth, such as pollution with chlorine and herbicides6 , 8 .
Question: How are underwater plants affected by various environmental factors?
For the last student exercise, students will use open inquiry to test variables of their choosing. Students will form a question related to plant needs and what factors have affected underwater bay grasses. Because it is difficult to obtain saltwater grasses, they will be performing tests on freshwater grasses instead, for example Cabomba or Elodea. Then students will be expected to make a list of materials to design the experiment themselves, also deciding how data will be collected and analyzed, modeling the process after previous exercises.
This curriculum unit was designed to guide students through the inquiry process, from structured to guided to open inquiry. Though the final exercise has a few parameters, the students are given the opportunity to create their own question and experimental design. Students are expected to make mistakes, and the teacher can help to guide the students in revising experimental design in order to more effectively test their hypotheses. This process encourages critical thinking skills and teaches students that being wrong is an important part of the scientific process.
Activity 1: Structured Inquiry
Question: How does acid rain affect living things?
Objectives: (1) Students understand the influence of various abiotic factors on living things, including water, temperature, pH, and sunlight; (2) Students understand the role of plants as the foundation of a food web or energy pyramid in an ecosystem; (3) Students use prior knowledge to make predictions of the outcome of an experiment; (4) Students follow a protocol to set up an experiment; (5) Students observe results, graph and interpret data and analyze the validity of their hypotheses; (6) Students work cooperatively.
Background: Students will have previously completed an activity and quiz about the water cycle, and how pollutants can move through the environment via the water cycle. First, ask students, "What do plants need to survive?" Give a 10-15 minute lecture explaining the importance of temperature, pH, water, and sunlight to plants, with special attention to pH.
Cooperative grouping: Students are arranged in groups of 3. One student is assigned the role of "coordinator," one student is "recorder," and one student is "materials manager." The coordinator's job is to read the instructions and coordinate the activities of the other group members. The recorder's job is to write or draw records of what the group is doing and their results. The materials manager is responsible for obtaining the necessary materials and assembling them as needed.
Materials for each group: 2 bottle biology set-ups (www.bottlebiology.org), soil, 1 jar of water at pH 7, 1 jar of water at pH 5, 100 ml graduated cylinder, triple-beam scale, ruler, 6 bean seeds.
Procedures: Students follow written protocol to set up the experiment to test the effect of acid rain on plant germination and growth. Students measure the same mass of soil and amount of water for each bottle-biology set up. Each group plants a total of 6 seeds at the same depth: 3 watered with pH-7 water and 3 with pH-5 water. Students will continue to water the plants with the same amount of water every other day. For each seed over the course of 2-3 weeks, students record daily (or every other day, depending on schedules) whether the seed has germinated, and after germination, the height of the plant. Students calculate averages for each pH group and record the data in a table. Then students will graph their group's plant height data over time. Students present their group data to the class, then all the class data is compiled to make a graph in Excel that is displayed on the smartboard. Students write a brief paragraph describing whether their group data and the class data supported their hypothesis, and why.
Assessment: The group will be assessed on the thoroughness of their lab notes, hypothesis, results, and conclusion. Each student will be assessed on participation. Students will be asked to write an "exit paragraph" describing what they learned about plant needs and abiotic factors, and the importance of repeated trials and constants in experiments.
Activity 2: Guided Inquiry
Question: Can we design a filter that will clean the water as quickly and effectively as oysters?
Objectives: (1) Students understand the importance of oysters to the health of the Chesapeake Bay ecosystem; (2) Students use inquiry skills to design a procedure independently, given the question and materials; (3) Students work cooperatively.
Cooperative grouping is as in Activity 1.
Materials for class demonstration: One 10-gallon tank, oysters, Chesapeake Bay water or sea salt and dechlorinated tap water.
Materials for each group: soil, water, measuring spoon, 2 clear containers, 250 ml graduated cylinder, triple beam balance, stopwatch (or cell phone), various household materials (cotton balls, cheesecloth, gravel, rubber bands, sponges, coffee filters, straws, newspaper, etc.)
Demonstration Procedure: Obtain live oysters from a seafood market or grocery store. Fill up two aquariums with water. If possible, use water from the Chesapeake Bay, but otherwise add at least 12 ml of sea salt for every liter of aquarium water. Add oysters to one tank, allowing oysters to acclimate to the water for 24 hours before the demonstration. Add algae and silt to both tanks, and record the amount of each added. Record the amount of time it takes for the oysters to filter the water until it is clear and record.
Alternative to Demonstration: If the demonstration is not possible, a time-lapse video is available at The Chesapeake Bay Foundation's website, at http://www.cbf.org/page.aspx?pid=1928. Oysters filter about two gallons per hour.
Elaboration: Students are given a chart of oyster harvest by season from 1950 to 2010 (from http://www.st.nmfs.noaa.gov/pls/webpls/FT_HELP.SPECIES). Ask students what people use oysters for. Discuss how humans have impacted the oyster population in both positive and negative ways.
Guided Inquiry Activity Procedure: Students design a filter that can filter water better than oysters. Filters will need to (1) make the water clearer and (2) filter more water per minute. As a class, students will decide on criteria for judging each group's filter. In groups of 3, students draw a plan of their filter device, then build it. Students add 5 ml of soil to 250 ml of water and mix thoroughly, then pour it through their filter. After one minute, students measure how much water flowed through the water and record the clarity of the water (see student worksheet). Students will then have an opportunity to alter the filter to improve it, then it will be judged by the judging committee according to their criteria. Assist students in calculating the filtering rate of their filtering device.
During the demonstration, start the timer when the oysters open their shells and stop timing when the water is clear.
1. How much water is in the tank? _________________________________
2. How much time does it take for the oysters to completely filter the water in the tank? ________________________________
3. Calculate the rate (ml/minute) it takes to filter the tank. _________________________
You will now try to design your own filter that will filter better than the oyster! Use any or all of the materials given to you by the teacher. Before you begin, draw a design of your filter on a separate piece of paper. Once your design is complete, begin building your filtering device. When you are finished, get it approved by your teacher.
- Measure 200 ml of water and pour into a 500 ml beaker.
- Add 3 g of soil and mix thoroughly.
- Place a collecting bucket under the filtering device.
- One person should start the timer when another person begins pouring the soil mixture into the filtering device.
- After 1 minute, quickly move the collecting bucket and replace it with the other collecting bucket to catch any extra water.
- Measure the water that went through the filter with a graduated cylinder.
How fast was your filtering device? Record the quantity of water filtered in 1 minute.
How clear did the water look after it was filtered? Did any dirt get through the filter?
What could you do to improve your filter?
Pour out the used water and throw away used materials. Clean any of the graduated cylinders or collecting buckets that are dirty.
Rebuild your filtering device, making improvements if necessary. Your improved filtering device will be judged by a judging committee and the best filter will win a prize.
Each group will demonstrate their filter and measure the amount of water filtered in a minute.
Was your filtering device the best? ___________________ How was yours different from other groups?
How was your filtering device different from oysters? Which was best?
Humans have had a huge negative impact on oyster populations. But we can also help! With your group, think of one thing you can do to help increase the population of oysters.
Educate! Make a poster on a separate piece of paper that tells people about the importance of oysters. Illustrate for people how oysters help the bay, how the bay would be affected if there were no oysters, and how people can help. Have fun and be creative!
Assessment: Formative assessment throughout the lab exercise. Worksheet graded for completion and correctness. Poster graded for creativity and correctness.
Activity 3: Open Inquiry
Question: How are underwater plants affected by various environmental factors?
Objectives: (1) Students will make predictions and design an experiment to test the effect of two environmental factors on underwater plants; (2) Students will interpret and analyze data to determine if the data supports their hypotheses; (3) Students will work cooperatively; (4) Students will understand how biotic and abiotic factors affect plant growth.
Materials per group: 3 jars, Elodea, plant food, soil, graduated cylinders, dechlorinated
water, lab notebooks
Procedure: Before the laboratory exercise, give a brief presentation to review plant needs, and how humans have impacted the water in which Chesapeake Bay plants grow. Students choose 2 environmental factors, such as light, sediment, or nutrients, and predict how they will affect plant growth. Students write out a procedure for how they are going to test the environmental factors they chose and how they are going to collect data. Students may need assistance with this process. Once the procedure is approved by the teacher, students set up the experiment. Students create a table to record data in their lab notebooks. Students take plant growth data each class for 2 weeks, then create a line graph and interpret the data. Students determine if their data supports their predictions and write a brief conclusion.
Assessment: Formative assessment throughout the lab exercise. Students will be assessed based on the completeness of their hypothesis, procedure, data, graph, and conclusion.
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