Explore the dynamic earth and ocean off Canada's Pacific coast
 

Deep Sea Lesson Plans:

Lesson 1: Discovering Neptune Canada

Lesson 2: Ecology of Deep Sea Ecosystems

Lesson 3: Food Webs

LESSON 3 (click here for PDF version)

Exploring Marine Food Webs with NEPTUNE Canada

Overview:

Students build on concepts and vocabulary learned in Lesson Two by constructing food webs for each of the three unique ecosystems at NEPTUNE CANADA Nodes.

Duration:

1 classroom session

Objectives:
Students will…
  • focus on the food requirements of organisms as part of their survival needs
  • compare and contrast marine food webs in ecosystems where photosynthesis and chemosynthesis are the primary processes
  • analyze roles of organisms as part of interconnected food webs
  • discuss the effects of species removal or reduction to food webs and ecosystems

Vocabulary:

 

 

 

Food Chain – a model that shows how food energy passes from one organism to another in a feeding pathway.

Food Web - a model that shows several different food chains and the connections between them

Trophic levels – “Trophic” is an old Greek word for “food”.   Trophic levels are used in food web models to describe the transfer of food energy among producers, consumers and decomposers.

Producer – organisms that can make their own food (also known as autotrophs).

Consumer – an organism, such as an animal, that gets its food by eating other organisms (also known as heterotrophs).

Detrivore – organisms that feed on bits of dead stuff.

Decomposer – organisms that get their food energy by breaking down the final remains of dead stuff.

Primary consumer (1o)– an animal that eats only producers.

Secondary consumer (2o)– an animal that eats a herbivore.

Tertiary consumer (3o) - a carnivore that eats other carnivores.

Top-level consumer (or Quaternary consumer (4o)) – carnivores at the top of the food chain or food web.

Bacterivores – animals that eats “producer” bacteria (primary consumer).

Herbivore – an animal that eats only producers (primary consumer).

Carnivore – an animal that eats other animals.

Omnivore – a consumer that eats both producers and consumers.

Microbes – single-celled organisms without a membrane-bound nucleus.  These organisms are the most ancient forms of life on earth.  Some of these microbes are primary producers through the process of chemosynthesis.

Plankton – organisms that drift at the mercy of the tide and currents.

Phytoplankton – single-celled aquatic algae that make their own food and are important organisms at the base of the aquatic food webs.  These powerful primary producers drift in the water column.

Zooplankton – animal plankton that consume phytoplankton and zooplankton. 

Seaweed – marine algae that make their own food by using photosynthesis (primary producer).

Extremophile – an organism that lives in extreme environments such as super heated water or toxic-laden environments.

Gas hydrate -a crystalline solid consisting of gas molecules, usually methane, each surrounded by a cage of water molecules. It looks very much like water ice.

*Definitions are from NEPTUNE Canada (www.neptunecanada.ca) and B.C. Science Probe 7 (Nelson). The key words provided are integral to this lesson plan.  If the Earth Sciences topics (eg. Tectonic Plates) have not already been covered in your class, you will need to teach the material prior to the NEPTUNE Canada introduction.

British Columbia PLO’s:

  • Grade 7 Science: Energy flows and matter cycles in ecosystems
  • Grade 10 Science B1:  Illustrate the cycling of matter through abiotic and biotic components of an ecosystem.
  • Grade 10 B1:  Explain relationships with respect to food chains, food webs and food pyramids, including producer, consumer, predation, decomposers and symbiosis.

Background:

1.  Introduction to Trophic Levels

Animals need energy every day so we can walk, run, work and play.  Where does this “energy” come from?  We get energy from the food we eat. Consider what you ate for dinner.  The food you crunched was made (or “synthesized”) by organisms in your food chain.   Food chains are made up of producers, consumers and decomposers.  At the beginning of any food chain are producer organisms that convert non-living molecules into food morsels called “sugars”. 

As you learned in lesson two, plants, phytoplankton and seaweeds make “sugars” through photosynthesis and certain microbes make “sugars” through chemosynthesis. These organisms are called primary producers because they are hard at work changing molecules into “sugars” and oxygen for us to eat and breathe.  Primary producers are the only organisms that can make “sugar” and oxygen, and without them, animals would have no food to consume. 

Consumers are organisms that can’t make their own food and eat other living things for energy.  Animals like us rely on finding tasty morsels to eat like plants or other animals.  If an animal eats a producer, like a plant or a seaweed, we call that animal a primary consumer or a herbivore.   Just like herbivores, animals that munch on microbes are also primary consumers but can be called bacterivores.  Primary consumers lead a tough life, they are destined to become food for other animals! Animals that feed on herbivores are called secondary consumers (or carnivores).  Carnivores that feed on other carnivores are called tertiary consumers or top-level carnivores. Animals with a diet of producers and consumers are called omnivores.  Critters that consume dead things are called detrivores and decomposers.

Before we go any further, try to figure out what kind of a consumer you are.  Are you a primary consumer (or vegetarian), a secondary consumer (hamburger lovers) or, perhaps a detrivore! You may be classified as an omnivore if you ate your vegetables and meat for dinner. If you consider all of the producers and consumers that went into your meal, you can construct a food chain.  By classifying who eats whom in this way, we can construct food chains or food pyramids.

2. Marine Food chains and Food Webs

Figure 1. Diagram of an energy pyramid comparing a sunlit Folger Pinnacle with a deep dark Endeavour Hot Vent.

Scientists track the transfer of energy by making models called food chains and food webs.   Food chains show who eats whom.  Left, is an energy pyramid showing two simple food chains of life at the Folger and the Endeavour ecosystems.
Important things to consider are the levels of the pyramid and its shape. Like rungs on a ladder, we classify the steps in the food chain as food levels or “trophic levels” (“trophic” in Greek means food). The pyramid starts with producers at its widest point and ends at the narrow top point with carnivores. This is no mistake as it takes a lot of producers to fuel the energy for herbivores. As we move up the food chain, the pyramid demonstrates that fewer and fewer animals are supported at each rung or trophic level. This is because lots of food energy is lost between trophic levels for many reasons including respiration, inefficient digestion and also by waste (did you eat your veggies?).

Something else to consider in this pyramid diagram are the two different types of primary producers.  You learned the differences between photosynthesis and chemosynthesis in Lesson Two.  Note that the Folger Passage and the Endeavour food chains have very different types of primary producers.

Food webs combine food chains together to show how organisms in the ecosystem are connected.  Food chains and food webs are usually drawn with arrows showing the food connections between producers, consumers and decomposers. Below is a food web diagram of some of the organisms living at the Folger Passage pinnacle site. 


Figure 2. Folger Passage Pinnacle food web

Consider the interconnectedness of species in this food web. How would a seal meet its survival needs if major prey species were hard to find?

From research you did earlier, you learned that the Folger Passage Node is located in shallow water. At the base of this food web, primary producers  use the sun’s energy to produce food to fuel the food web. You also know that the Endeavour and Barkley Canyon nodes are deep and dark ecosystems powered by chemosynthesis. 

Materials:

  • Critter Cards made in Lesson Two
  • Materials to finish Critter Cards: coloured construction paper, markers, glue sticks.  A a quick option is to make headbands using the name of each animal.
  • Materials to make food web displays (cardboard, string, pushpins, scissors, markers)
  • Copy of Organisms and Food Web Roles lists (for teachers)

Procedure:

  1. Begin by introducing the food chain, food web, and trophic level concepts.  Draw in examples from the three NEPTUNE Canada ecosystems (Folger Passage, Barkley Canyon, and Endeavour Ridge).  There are many wonderful resources on the SOLE Website to help you.  You can use the vocabulary list on the board or as a handout for reference during the lesson.  (Optional: Have students add to the vocabulary lists from Lesson One and Two)
  2. In Lesson Two, students gathered information on individual “critters” to make up their critter cards.  At this point students must decide which trophic level their critter belongs in (primary producer, primary consumer, secondary consumer, tertiary consumer).  Teachers can use the Organisms and Food Web Roles sheet for some quick answers!  Lead a discussion on food chains and how to link the chains into an ecosystem food web.  Ask all the students to organize themselves into groups (within the Node teams), so that all the producers are together, all the primary consumers are together etc.  Ensure the students are in the proper trophic level group.
  3. Assign each trophic level a colour.  Green for producers; blue for primary consumers (herbivores and bacterivores); red for upper-level consumers (carnivores); and white or yellow for detrivores.

The food webs can be displayed in a number of ways:

Option 1: Food Web String Game

  1. Get each student to cut their Critter Card in half. Each half should then be glued to the appropriate piece of coloured construction paper. Alternatively, students can display their critter headband.
  2. Get the students to stand in a circle (3 circles for 3 Nodes) with their Critter Card displayed.  Begin by giving a ball of sting to a producer.  Have the student representing the producer toss the ball of string to an organism that consumes them (a primary consumer).  Continue passing the string up or down trophic levels (either to an organism that consumes them or to an organism that they consume) until all critters are included.  Note: Some students may get the string a few times, this is OK.  Omnivores are particularly interesting as they’ll link together two different trophic levels!
  3. Keep the web of life tight!  After all of the laughing, you can create chaos by removing critters (students) from trophic levels, one by one.  As the string starts to slacken, how does the web of life start to unravel?  Discuss what happens to the food web, to biodiversity, and to ocean survival as species go extinct.
  4. When the string game is done, have each team present and explain their food web to the other ecosystem teams

Option 2: Cardboard Food Web Display

Another way to use the information researched by the students is to construct a cardboard display.  This activity is found in BC Science Probe 7:

  1. Divide up a piece of cardboard into 4 trophic level sections with producers at the bottom; primary consumers/herbivores next; followed by secondary consumers/carnivores at the top; and detrivores & decomposers to the side.
  2. Make labels (or use the Critter Cards) with the name of each organisms you researched and use pushpins to fasten the label in the correct trophic level (omnivores get two pushpins)
  3. Use thread or string to connect each organism with what organism eats it.

Option 3: Food Web Mobiles

  1. Use the complete critter cards to create a Food Web Mobile. Each NEPTUNE Canada Node ecosystem will have one mobile.
  2. The students can use cardboard cut into a circle for the base, then hang the critter cards however they like.  Get the students to draw the habitat of their Node on the underside of the cardboard, so when you look up at the mobile, you know that you are looking at the Endeavour Hot Vent ecosystem (for example).
  3. Use string to connect the hanging cards, showing the relationships among the organisms represented.
  4. Display the mobiles with pride in the classroom.

Discussion:

  • What happens if you actually remove one or more species at a single trophic level; at multiple trophic levels?
  • This is a good time to discuss important conservation projects that the class can participate in or to celebrate conservation achievements by individuals in the class, the school, community or our Province.
  • List some basic similarities and differences among marine food webs and land-based food webs.

Extensions:

Extension 1:  Puzzling things out
Using all of the new information gained, students can make word games, crosswords or even a jeopardy game.  Send your games back to us for posting on our website.

Extension 2:  Symbiosis
Symbiosis is an amazing interaction between organisms.  Students can continue to dive into this amazing partnership between animals by venting their creativity!  The animal giants,  “tube worms, giant clams, and giant green anemones,  can be brought to life in your classroom by make models (life size would be scary), costumes, posters or slideshows.  Students can compare and contrast symbiotic relationships in photosynthetic (giant green anemones) v. chemosynthetic (tube worms and clams) habitats. 

Extension 3: Art
In Lesson One, students may have drawn murals of each of the three marine habitats (if not, they can start one now).  Have the students show what they have learned by adding all the organisms and relationships they have discovered to the habitat mural.  These murals then provide a colourful reference for all students in the class during future discussions on ecosystems. 
***We would love a photo of these murals for our website.  

 

Resources: 

For Students: 
1. Making your own food chains/webs
2. The Amazing anatomy of hot vent tube worms!  Into the Abyss: Tubeworm anatomy

For Teachers and Students:

  1. Teaching about Hydrothermal Vents.
  2. Teaching about Cold Seeps. Project Oceanography: a lesson plan about cold seeps, photosynthesis and chemosynthesis, and symbiosis.
  3. Cold Seep and Associated Communities of the Gulf of Mexico, a summary for biologists and scientists (PDF)

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