In today's Daily Do, How can ecosystems survive without sunlight? students engage in science and engineering practices and use patterns as a thinking tool to make sense of an underwater ecosystem void of sunlight. Students build on prior knowledge about ecosystem dynamics and use the Cross-Cutting Concept of Matter and Energy to use as a lens to make sense of this new ecosystem. This phenomena explores how the introduction of a new species to an ecosystem can affect the existing interactions and dynamics of that ecosystem.

Begin by having students think about what they remember about ecosystems including food chains/webs and interactions between organisms and their environment. Have them discuss with a partner the components and interactions between components in an ecosystem and then have them share as a whole group. As students share, document their thinking based on prior learning. Some patterns that should emerge are:

• ecosystems contain both living and nonliving things
• ecosystems can change over time
• ecosystems contain food chains and food webs
• food chains/webs contain producers, consumers and decomposers
• plants "make their own food" from the Sun through photosynthesis
• the Sun provides energy for the ecosystem (all living things)
• energy flows through an ecosystem and matter cycles through an ecosystem

If students don't bring up the Sun and/or photosynthesis, you might ask, "What is the source of energy in an ecosystem? Why do you say so?" and then allow them turn and talk with a partner before sharing their ideas with the class. Students should surface ideas about photosynthesis and the Sun as the driver for this process.

Now that the role of the Sun and the importance of photosynthesis has been established, introduce the phenomenon by sharing three pictures of an ocean ecosystem (below). Allow students time in the "'alone zone" to make and record observations of the ecosystem. Next, have students share their noticings with a partner or small group. Common noticings include:

• The objects look like they are made of stone with plants/mold growing on them.
• The objects are white and brownish green in color.
• One picture looks like it has crabs in it so we think these are from underwater.
• One picture has specks of white (we think they are crabs) on the rock.
• There seems to be dark smoke coming out of one of the rocks.
• The background in all the pictures is black. We think these were taken in the dark with a flash or a light.

Tell students that what they are looking at are called hydrothermal vents. Share that hydrothermal vents are found near tectonic plate boundaries and the one they are about to see is located along the Marianas Trench (reference map below). Show students the Hydrothermal Vent video (below) recorded during the 2016 Deepwater Exploration of the Marianas by the NOAA Office of Ocean Exploration and Research. As students watch the video, have them write down any questions they have about what they see. (Do not ask students to share questions at this time.)

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Guidance: Allowing students time to share with each other helps to surface prior knowledge and provides opportunities for them to share related previous experiences. At this point, students should only be discussing and sharing ideas and not trying to figure out the answers to their questions. Some common misconceptions that may surface through student discussion include:

• algae are plants
• plants and algae can photosynthesis in the dark
• animals that live around the vents just feed on dead things that float down to the sea floor
• animals are white so they can be seen in the dark

At this point it is important not to try to correct these misconceptions as many of these ideas will come out in the learning throughout the rest of the lesson. The lesson is designed to allow students to figure out the important science ideas over time through the use of science and engineering practices which gives them opportunities to change their thinking based on new evidence.

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After viewing the video, ask students if they remember how deep underwater the hydrothermal vent is located. If no one can recall the depth, tell them the hydrothermal vent is about 3200 meters below the ocean surface. Quickly survey students (ask for a thumbs up/thumbs down response, for example), "Do you think sunlight penetrates that far below the ocean surface?" Then, share the graphic, Distance Sunlight Travels in the Ocean, and ask them the question again. Come to agreement sunlight does not travel deep enough to reach the hydrothermal vent ecosystem.

Now that student know sunlight doesn't reach the hydrothermal vent ecosystem they observed, give them time to add any new questions to their list. Next, have students share and discuss their questions in small groups. Instruct students to choose one question based on the observations they made of the hydrothermal vent ecosystem using the pictures or video that they would like to share with the whole group. Encourage each student in the group to choose a different question. Bring students back together and ask them to share with the class. Common questions include:

• How hot is 300 degrees C?
• How can animals live there when it is so hot? (Some may ask how animals like crabs avoid being cooked.)
• Why are the animals white?
• What is all the white stuff on the rock - shouldn't it be black because of all the smoke?
• What do the animals eat?
• How do plants grow down there?
• Is algae growing on the rocks or is that stuff from the smoke?
• How can plants/algae survive down there with no sunlight?
• Does light come from somewhere else since sunlight can't reach the vent?

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Guidance: Students may share their questions in a variety of ways including writing them on a "sticky note" and posting it in a shared classroom or virtual space like Jamboard or Padlet or reading their question aloud to the group and having the teacher record it on a class list. It is important all students share a question and that all questions are acknowledged as this promotes both participation and student engagement. This also helps attend to issues of access and equity.

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Gathering Ideas for Investigations

Next, prompt students to think about how they might start figuring out the answers to their questions by asking, "What kinds of investigations could we do and/or what additional information might we need to figure out the answers to our questions?" Ask them to discuss their ideas with their group members. After a short discussion, have students share at least one investigation idea or additional information they would need to figure out how organisms can live in a completely dark, hostile environment. Some student ideas include:

• Research the hydrothermal vent ecosystem to see what kinds of living and non-living things are down there.
• Set up investigations to see if plants/algae can survive in the dark.
• Find out what the animals that live there actually eat.

After all the groups have shared their ideas for investigations or additional information, ask students what they think they should figure out first. Many students will want to know more about the organisms they observed living on and around the hydrothermal vents and what other organisms might live down there. Students may also want to know how common hydrothermal vents are - do they occur all along (tectonic) plate boundaries or are there just a few of them? Tell students scientists don't know the full extent of hydrothermal vents but there are several sites that have been explored. Then tell students you would like them to observe another hydrothermal vent ecosystem from a different location.

Show the video Giant Black Smoker Hydrothermal Vent (below). Ask students to jot down any information they think might help them answer their questions or other information they think might be important.

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Guidance: Ideas for investigations will vary depending on prior learning and previous experiences, especially around the science ideas related to photosynthesis. Having students think about and suggest ideas to investigate the answers to their questions helps build problem-solving skills and allow opportunities for students to connect previously-learned science ideas to a new context. Use these activities and discussions as formative assessment opportunities to see what prior learning, life experiences and interests your students are bringing with them into the classroom. At this point, it is not necessary to correct any misconceptions or incomplete ideas about these science ideas as they will have opportunities to change their thinking over the rest of the Daily Do lesson.

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Students will gather several pieces of information from the video about the hydrothermal vent including the water coming out of the vent is full of chemicals and material that makes up the vent is very hot. Now that they know a little more about the hydrothermal vent ecosystem, ask them to work with their small group to brainstorm ideas about how life can exist and be sustained at a hydrothermal vent without sunlight. Have small groups share their ideas with the class. Their ideas could include:

• Organism that live there just eat things that float down from the surface so they don't need any light.
• Organisms feed off the minerals/chemicals that come up from the vent.
• Since plants can't grow without sunlight something else must be the producer in the food chain/web (or "be at the beginning" of the food chain/food web).

Prompt students to think about the process of photosynthesis and how the process helps animals live and survive. Students should come to the conclusion that photosynthesis provides animals with food and oxygen. Give students time to think about and record any new questions they have. New questions that arise may include:

• How do the organisms living on and around the hydrothermal vent get oxygen?
• Do these organisms even need oxygen?
• Does oxygen come out of the hydrothermal vent? We didn't notice oxygen on the list of elements in the video.

At this point students have to grapple with big science ideas that seem contradictory to the ideas they learned in previous grades. Students have figured out:

• Organisms live deep in the ocean by hydrothermal vents that are really hot - around 300 to 400 degrees Celsius. Hotter than boiling water.
• Sunlight doesn't reach that far beneath the ocean surface, so organisms that get their energy from photosynthesis like plants and algae can not live there.
• Hydrothermal vents occur near tectonic plate boundaries (near trenches and spreading centers).
• Organisms that live by the vents seem to be mostly white in color.
• The water coming out of the hydrothermal vents are filled with chemicals.
• There is a food web in the deep ocean that does not depend on plants and algae.

These things students figured out raised new questions:

• How do organisms get the food (energy) they need without photosynthesis? The sun drives the flow of energy in every other ecosystem we have observed up until now.
• How do the organisms that live on and around the hydrothermal vents get oxygen? Does the ocean water contain enough oxygen for them to survive or is oxygen coming out of the vent?
• How can organisms live in water that is so hot and full of toxic chemicals?
• In the pictures and videos we saw some organisms like crabs and worms, but does anything else live down there?

Tell students you found a short interactive activity that provides information about some of the organisms that live in hydrothermal vent ecosystems. Have students complete the NOAA Chemosynthesis Food Web Activity individually or with a partner.

NOTE: This activity runs using Adobe Flash Player and will be replaced with another similar activity in an updated version of this lesson.

Next, ask students to share their noticings with a partner and then with the class. Student noticings could include:

• Way more organisms live down there (at hydrothermal vents) than we thought.
• The food web seems to start with chemicals.
• Bacteria are the beginning of the food chain/web (primary producers) and not plants.
• There are many different interactions between the organism just like other food webs we have experienced/observed in the past.

Give students some time to reason through what they have figured out and synthesize this new information. Ask students if they have everything they need to explain how an ecosystem can exist and survive at hydrothermal vents like we are able to for ecosystems driven by photosynthesis. Answers here will vary, some students will be confident they can while others think they need more information.

Have students work in their small groups to develop an initial explanation of the interactions between organisms within the hydrothermal vent ecosystem. Tell students that developing an initial explanation at this point is to help them synthesis ideas and organize their thinking; they should not worry about getting the "right" answer. Encourage them to either create and compare lists of components/interactions in each ecosystem or draw models of the two systems and compare them side-by-side to look for familiar patterns. Prompt students to think about how this might help them figure out the dynamics of the hydrothermal vent ecosystem.

As students work on their explanations, tell them to record any new questions they have. New questions could include:

• How do bacteria make their own food?
• Plants make their food using CO2 from the air - do bacteria need CO2? Where do they get CO2?
• If bacteria don't need CO2 to make their own food, what do they need and where do they get it? From the water coming out of the hydrothermal vent?
• What is chemosynthesis?
• Are chemosynthesis and photosynthesis similar, but different?

As a class, go back to the idea of photosynthesis and the role that it plays in an ecosystem. What are the inputs and outputs of the process? After a brief discussion, present students with the chemical equation for photosynthesis (shown below) and ask them individually record what they notice. Ask students to share their noticings with a partner before asking them to share with the class. Noticings include:

• The chemical equation involves carbon (C), hydrogen (H), and oxygen (O)
• There are two compounds on each side (two reactants and two products)
• The left side is carbon dioxide and water and the right side is oxygen and something else..maybe sugar?
• There is the same amount of stuff (total number of elements) on each side even though the numbers are in different places.
• Energy from the sun is needed to start this chemical reaction.

Students will likely come to the conclusion that they need to take a closer look at the chemicals in the water coming out of the hydrothermal vent and the ocean water around the vent. Students may recall seeing "simple chemicals" listed on the Chemosynthetic Food Web. They may also remember learning from the Giant Black Smoker Hydrothermal Vent video that water coming out of the hydrothermal vent contains minerals. Ask students if it makes sense to compare the chemicals identified in the food web activity to the chemicals in the chemical equation representing photosynthesis.

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Guidance: Students should have prior knowledge gained in middle school about chemical reactions including reactants (inputs), products (outputs), and that matter is conserved. However, if students do not have this prior knowledge it is not necessary that you stop and teach it directly. Instead, have students share what they notice. As students share you can give them more specific terms. For example if a student states that they notice there are two sets of things on either side of the arrow you can tell them the items to the left are reactants, the items to the right are products and that the arrow indicates that a chemical reaction has occurred.

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Now that students have used the chemical equation for photosynthesis to identify the components (elements and compounds), inputs (reactants) and outputs (products), have them look at the chemical equation for chemosynthesis below. Tell students this equation represents only one of many different chemical equations for chemosynthesis (the inputs and outputs for chemosynthesis can vary depending on the environment in which it occurs). Have students work in small groups to identify the components, inputs and outputs of chemosynthesis. Then ask them to compare the process of chemosynthesis with the process of photosynthesis. As you move around the room, listen for students to share ideas about the C, H, O compound. Ask them what they think this compound is; depending on students' background knowledge, some may recognize the formula as simple sugar. Be sure to call on these students when you bring the class back together to share their noticings.

Students should notice:

• Chemosynthesis involves the same components as photosynthesis, but also involves sulfur (S).
• Carbon dioxide is a reactant in both chemical reactions.
• Both chemical equations involve water, but in photosynthesis water is a reactant and in chemosynthesis water is a product.
• Both chemical equations involve oxygen; in photosynthesis, oxygen is a product and in chemosynthesis oxygen is a reactant.
• Both chemical equations include a compound made of carbon, hydrogen, and oxygen as a product. Some students may also notice the ratio of carbon, hydrogen, and oxygen is 1:2:1 in both chemical equations.

After the groups have shared, focus the discussion on the compound containing the elements C, H, and O (simple sugar). Prompt students to share what they know or think they know about this compound and how it is used by both plants and animals. Students will likely share that plants use sugar as both a source of energy and for growth and development of new structures.

Next, prompt students to think about what the simple sugar produced by chemosynthesis could be used for based on their knowledge of photosynthesis. Students will likely share the idea that the bacteria use the sugar produced through chemosynthesis similar to the way plants use sugar. is used taking place fuels the bacteria. Now share the How Giant Tube Worms Survive at Hydrothermal Vents video (below) with students to provide additional information about how chemosynthetic bacteria support food webs in hydrothermal vent communities.

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Guidance: Students who understand how the Sun's energy drives photosynthesis may question where the energy comes from to make the sugar in the process of chemosynthesis. In this lesson, it is to adequate to tell students that when a chemical reaction occurs, energy is both released and absorbed. If students have the appropriate chemistry background, you might choose to talk about endothermic and exothermic reactions and bond energy and how the processes of photosynthesis and chemosynthesis involve different types of chemical reactions.

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Now that students have figured out more about hydrothermal vent ecosystems, have them use a "comic strip" scaffold to create a model to explain how ecosystems exist and thrive in the absence of sunlight and predict what would happen if the hydrothermal vent became extinct (stopped ejecting hot, mineral-rich water).

To create the comic strip scaffold, have students divide a sheet of paper into 3 sections. Explain that the sections, or frames, of the comic strip represent the hydrothermal vent ecosystem over time:

• Frame 1: The hydrothermal vent is active and ejecting large amounts of hot, mineral-rich water (present time).
• Frame 2: The hydrothermal vent has just become extinct and is no longer ejecting hot, mineral-rich water (days after extinction).
• Frame 3: The hydrothermal vent has been extinct for a long period of time (years after extinction).

Remind students that their models should represent the ecosystem components, interactions between components, and how the components are interacting using appropriate science ideas using words, symbols and/or pictures.

As you move from group to group, you might ask students the following questions to move their thinking deeper:

• Which components are represented in all of the frames? Which components are unique to each frame?
• How are component A and component B interacting? How might you represent this interaction?
• Where does organism A (B, C, etc.) get its energy?
• Where is matter coming from that enters this ecosystem?
• What happens to matter as it moves within the ecosystem?
• Where does matter go that leaves the ecosystem?

You might choose to have students work first in the Alone Zone (independent thinking time) and then in small groups of three or four to create a group consensus model.

Next, have the class engage in a gallery walk to observe other individual or group models. As students observe each model, have them use sticky notes to post one thing they like about the model (a component represented they didn't include on their own model, the method used to represent an interaction between components, etc.) and one question they have about the model. When the gallery walk is complete, allow time for students to reflect on the feedback provided by their peers and add to or change their models. Then engage students in a whole groups discussion to share their predictions. Predictions will vary in that some student may think the hydrothermal vent ecosystem will die as soon as the hydrothermal vent becomes extinct because the bacteria don’t have a source of chemicals for chemosynthesis. Others may think the “unused” chemicals floating in the water after the vent is extinct will continue to support chemosynthesis. As students share, prompt them to use evidence and reasoning to support their predictions.

Show students the video clip, Smoking Chimney and Pompeii Worms (below), of a hydrothermal vent nearing extinction. Next, have students read the Galapagos Rift Mission log recorded on May 21, 2002, Life Cycles of Vent Communities – So Much to Learn.

Now that students have more complete understanding about the dynamics of hydrothermal vent ecosystems, engage them in a discussion about what they learned from the video clip and the reading. Does this new information supports or refutes their predictions? Have students revisit their models and update them based on their new understanding. If they haven't done so already, prompt students to include an explanation for why hydrothermal vent ecosystems eventually die after the vent becomes extinct. A sample explanation is shown below:

When the chemicals stop coming out of the vent the ecosystem will die. Since the bacteria survive on the chemicals being spewed out from the vent, when the vent stops the bacteria die. Since the bacteria is the basis for the ecosystem and serve as the primary producer there is nothing for the primary consumer to eat. This will cause a cascading effect that results in the total collapse of this ecosystem.

Finally, revisit students' questions and have them think about all the things they have figured out about hydrothermal vent ecosystems. As students share what they have learned also encourage them to think about what they still have left to figure out about these ecosystems. Many students will want to know if ecosystems like this exist in other places. Tell students that there are other ecosystems that exist in extreme environments. Use this discussion to help guide next steps.

It is important for students to know chemosynthesis is not specific to hydrothermal vents. Consider having students investigate other environments in which chemosynthesis occurs such as cold seeps, mining waste run-off, and hot springs.

This Daily Do lesson can be used as a starting point to figuring out several big science ideas. In future lessons students could:

• dig deeper into plate tectonics and the Earth processes that form hydrothermal vents (HS-ESS1-5 or HS-ESS2-1)
• explore the chemistry needed to explain the process of chemosynthesis (HS-PS1-1 or HS-PS1-7)
• figure out how vent ecosystems maintain equilibrium (with some modification to the following performance expectations: HS-LS2-3, HS-LS2-4, and HS-LS2-5).
• investigate other ecosystems in which chemosynthesis is the driver for matter and energy (examples of other systems shared in the photosynthesis/chemosynthesis video)