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What is an Ecosystem?

Hudson River Ecosystem Unit Plan

Now that your students have an understanding of the Hudson River's geography and the watershed that feeds it, it is important to teach them the concept of an ecosystem. Ecosystems are defined units of study with boundaries that are often chosen for convenience. The connections between ecosystems are so strong that some ecologists argue that all life on Earth is held in a single ecosystem-the biosphere, with humans as the dominant species. However ecologists usually find it convenient to study smaller subunits and then conceptualize how the whole is put together. Here students will learn about the Hudson River Ecosystem. The Hudson's ecosystem is connected by the streams, rainfall, runoff and seepage to the forest, atmosphere, and groundwater systems that are in its watershed.

Day 1-2:

Hudson Food Webs:

Objective: Students will know how an invasive species has changed the Hudson River food web and be able to explain the impact of the introduction of the zebra mussel on the food web.

Activities:
1. Students brainstorm a list of organisms that live in the Hudson. 2. Students use online food web visuals to learn about different communities that live in the Hudson River. 3. Using stations, students view different species of plankton with microscopes (either prepared slides or live samples). 4. Students draw the main plankton species 5. Using the provided Hudson River food web drawings and reading, as well as the data in the lab sheet, students determine the changes that have taken place in the river food web since the arrival of zebra mussels. 6. Students create pre and post-invasion food webs.

Assignment: Read “Hudson Food Webs” the night before and complete online portion of lab packet; complete lab packet

Materials: prepared slides or live specimens of phytoplankton: diatoms, chlorophyceae (often called green algae), cyanobacteria; and zooplankton: rotifers, cladocerans (if you can get more than one species of cladoceran, that would be great; the most abundant in the Hudson is Bosmina freyi), copepods (the major forms are Cyclops and copepod nauplii-these are juvenile or young forms)., microscopes , computers with internet access (this can be assigned as homework the night before), copies of the food web reading & worksheet

Day 3-4:

Biomanipulation:

Objective: Students will be able to explain how zooplankton grazing affects the food web of an aquatic system.

Activities:
1. Students set up experiments to measure the reduction of algae in an aquatic system. 2. Students monitor their experiments over a two-week time period. 3. Students report on their results.

Assignment: Read “Eutrophication” for homework

Materials: natural algal populations or cultures such as Chlorella, zooplankton cultures such as Daphnia, Bosmina, Cyclops, fishbowls or small aquaria

Day 5-6:

An Aquatic Ecosystem:

Objective: Students will know how an aquatic ecosystem works and be able to collect representative organisms, identify the organism and its trophic level, and create a food web of a local aquatic ecosystem.

Activities:
1. Students visit a local stream, pond, creek, or river and collect macroinvertebrates 2. Students sort macroinvertebrates and identify each species using a dichotomous key 3. Students decide on trophic levels and construct a possible food web for their ecosystem

Assignment: Complete lab report

Materials: Day 1: nets, waders, collecting trays, magnifying glasses, collecting jars, permanent markers, tweezers, strainers, macroinvertebrate keys, isopropyl alcohol (if you need to preserve the animals for the next class period) Day 2: dissecting microscopes, lights, Petri dishes, magnifying glasses, reference keys, tweezers, pipette

Day 7:

Ecosystem Disturbance:

Objective: Students will know the effects of deforestation on an ecosystem and be able to explain the impacts of a stream using data.

Activities:
1. Students brainstorm about the impact of deforestation on an ecosystem 2. Students use data to answer questions 3. Students present and discuss results

Assignment: Complete worksheet questions

Materials: Copies of worksheet, photos (overhead or printed)

Day 8-10:

The Nitrogen Cycle:

Objective: Students will know the impact of various forms of nitrogen on aquatic and terrestrial ecosystems, and be able to draw a diagram showing the movement of nitrogen in these systems.

Activities:
1. Students complete the nitrogen cycle “game” and discuss the different pathways and forms nitrogen can take in the environment. 2. Students decide if they want to investigate the impacts of excess nitrogen on aquatic or terrestrial ecosystems. 3. Students design and set up an experiment to test their hypotheses. 4. Students collect data every week, and compile this data into a lab report.

Assignment: Complete game worksheet; begin lab packet using online visuals

Materials: For the game: copy and laminate the Nitrogen Cycle Game descriptions, worksheet copies, one dice per station. For class discussion: Hudson Nutrient Cycles powerpoint, Nitrogen Cycle visuals, copies of the worksheet “Nitrogen cycle computer assignment”. For experiment: see lesson plan, as materials vary based on aquatic or terrestrial manipulation

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