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Build a marine food we.doc - Science Learning Hu

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Build a marine food we.doc - Science Learning Hu

     Context > Life in the Sea > Teaching and Learning Approaches > Build a marine food web

    STUDENT ACTIVITY: Build a marine food web

Activity idea

    In this activity, students build their own food web using images of organisms from the marine ecosystem. This activity can be done indoors on paper or outdoors on a tarmac surface using chalk.

By the end of this activity, students should be able to:

    ; understand the difference between a food chain and a food web

    ; understand that food webs are made up of producers, consumers and decomposers ; build and revise their own food web to show the interdependence of organisms in an

    ecosystem

    ; understand the potential impact of the removal or reduction of one species on the rest of

    the food web.

Introduction/background notes

    What you need

    What to do

    Discussion questions

    Possible variations

    Student worksheet

    Trophic pyramid diagram

    Tuna sandwich diagram (transfer of energy)

    Organism cards (small)

    Organism cards (large)

Introduction/background

Feeding relationships are often shown as simple food chains’, but in reality, these relationships

    are much more complex, and the term food web more accurately shows the links between

    producers, consumers and decomposers.

    A food web diagram illustrates ‘what eats what’ in a particular habitat. Pictures represent the organisms that make up the food web, and their feeding relationships are typically shown with arrows. The arrows represent the transfer of energy and always point from the organism being eaten to the one that is doing the eating.

What you need

; Student worksheet for each group

    ; Large piece of paper for each group

    ; Set of organism cards for each group

    ; Blu-Tak

    ; Pencils

What to do

1. Have students explore the Marine ecosystem interactive and complete the student

    worksheet. This could also be explored as a class using an interactive whiteboard or data

    projector. Additional information can be found in the Looking Closer articles for this context.

    2. As a class, discuss what the students know about food webs. The discussion could focus on

    producers, consumers, decomposers, the trophic pyramid, energy loss in food webs (tuna

    sandwich) and human impact on food webs. It may be helpful to watch the video clip

    Understanding food webs.

    Common student alternative conceptions about food webs include:

     1 ? 2007-2009 The University of Waikato

    www.sciencelearn.org.nz

     Context > Life in the Sea > Teaching and Learning Approaches > Build a marine food web

    ; top consumers eat everything below them

    ; organisms shown in food webs represent individuals rather than populations of

    organisms

    ; an organism that is not directly linked to another by a feeding relationship will not be

    affected if that organism is removed.

    3. Give each student or group a set of organism cards (small). You may want to start the food

    web building activity by asking students to use their organism cards to build simple food

    chains before they move on to build a web. For example:

    4. Working on a large piece of plain paper, ask students to use the organism cards and the

    information gathered on their worksheet from the Marine ecosystem interactive to build

    their own food web using Blu-Tak so they can move the cards around.

    5. Have them use pencils to draw arrows showing connections between the different

    organisms. (The arrows represent the transfer of energy and always point from the

    organism being eaten to the one that is doing the eating.)

Discussion questions

    ; Can you make any connections on your diagram that aren’t a feeding relationship? (For

    example, bryozoans provide a nursery habitat for young fish.)

    ; Are some organisms more important than others?

    ; Why are decomposers important in a food web?

    ; Do you think anything is missing from your food web?

    ; Where do humans fit in the marine food web?

Possible variations

Estuary habitat

    Before step 4, ask students to draw their own poster diagram of an estuary (without any organisms in it). They can then Blu-Tak the organism cards into the appropriate habitat on their poster before completing the rest of the activity.

Outside version

    Run the activity outside (you will need one set of large organism cards and some chalk): 1. Divide the class into groups of 23 and find a suitable area of tarmac outside (preferably

    flat with few markings). Give each group one organism card (large) and some chalk. 2. Ask students to spread themselves out in the tarmac area. 1 member of the group should

    stay in the same spot holding the card at all times. The other group member(s) should

    move around and explore the other cards. (All group members should have the opportunity

    to move around at some stage.)

    3. When 2 groups agree that their cards should be linked, they should draw a chalk arrow to

    illustrate the feeding relationship. (Remind the students that the arrows represent the

    transfer of energy and always point from the organism being eaten to the one that is doing

    the eating.)

Scenarios

     2 ? 2007-2009 The University of Waikato

    www.sciencelearn.org.nz

     Context > Life in the Sea > Teaching and Learning Approaches > Build a marine food web

    The effect of removing or reducing a species in a food web varies considerably depending on the particular species and the particular food web. In general, food webs with low biodiversity are more vulnerable to changes than food webs with high biodiversity. In some food webs, the removal of a plant species can negatively affect the entire food web, but the loss of one plant species that makes up only part of the diet of a herbivorous consumer may have little or no effect.

    Some species in a food web are described as keystone species. A keystone species is one that has a greater impact on a food web than you would expect in relation to their abundance. The removal of a keystone species characteristically results in a major change, in the same way that removing a keystone from an arch or bridge could cause these structures to collapse. In Fiordland, the New Zealand sea star is a keystone species that controls the numbers of the species it feeds on, for example, mussels. If the sea star is removed, this could cause a large increase in the numbers of mussels and this has flow on effects throughout the food web.

    After the students have shown connections between the different organisms (on both the inside and outside version of the activity) introduce one of the scenarios (For the inside version, you could give different groups a different scenario.):

    A. A large commercial fishing company triples their annual catch of red cod in the area. B. The land on the edge of the estuary is converted to intensive farming. There is a big

    increase in agricultural run-off and nutrients into the estuary. This increases the risk of

    phytoplankton blooms.

    C. Due to increased carbon emissions, the ocean is becoming more acidic. Bryozoans and

    other shelled animals will no longer be able to make shells.

    Ask the students to revise their food web to show what they think might happen to the food web based on the scenario.

Scenario Possible outcomes

    A. Annual catch of Increase in zooplankton, small fish and juvenile sea stars. Decrease in

    red cod increased squid, sea birds and dolphins some top predators may disappear

    altogether. Damage to the seafloor affecting seaweeds and bryozoans.

    Increase in the number of bycatch (non-target species), for example,

    this could reduce populations of crabs, dolphins and squid.

    B. Run-off Additional nutrients in the sea can lead to excessive phytoplankton

    growth that results in ‘blooms’. When these large numbers of organisms

    die, the sharp increase in decomposition of the dead organisms by

    oxygen-using bacteria depletes oxygen levels. In some cases, this can

    result in the death by oxygen-starvation of large numbers of other

    organisms such as fish.

    C. Ocean Any animal that produces a calcium carbonate shell will find it much

     levels in the atmosphere rise and oceans acidification more difficult to do so as CO2

    become more acidic. Organisms could grow more slowly, their shells

    could become thinner or they might dispense with shells altogether. This

    may lead to the loss of cockles and other bivalves as well as the

    important bryozoan habitats for juvenile fish.

     3 ? 2007-2009 The University of Waikato

    www.sciencelearn.org.nz

     Context > Life in the Sea > Teaching and Learning Approaches > Build a marine food web

Student worksheet

     Decomposer Producer Consumer Eaten by… Feeds on… Other information…

     Zooplankton ; ; ;

     Seaweed ; ; ;

     Red cod ; ; ;

     Sea stars ; ; ;

     Phytoplankton ; ; ;

     Dolphins ; ; ;

     Crabs ; ; ;

     Cockles ; ; ;

     Arrow squid ; ; ;

     Bryozoans ; ; ;

     Sea birds ; ; ;

     Bacteria ; ; ;

     The Sun

     4 ? 2007-2009 The University of Waikato www.sciencelearn.org.nz

     Context > Life in the Sea > Teaching and Learning Approaches > Build a marine food web

Trophic pyramid

     5 ? 2007-2009 The University of Waikato

    www.sciencelearn.org.nz

     Context > Life in the Sea > Teaching and Learning Approaches > Build a marine food web

Tuna sandwich

     6 ? 2007-2009 The University of Waikato

    www.sciencelearn.org.nz

     Context > Life in the Sea > Teaching and Learning Approaches > Build a marine food web

Organism cards (small)

     7 ? 2007-2009 The University of Waikato

    www.sciencelearn.org.nz

Context > Life in the Sea > Teaching and Learning Approaches > Build a marine food web

8 ? 2007-2009 The University of Waikato

www.sciencelearn.org.nz

Context > Life in the Sea > Teaching and Learning Approaches > Build a marine food web

9 ? 2007-2009 The University of Waikato

www.sciencelearn.org.nz

     Context > Life in the Sea > Teaching and Learning Approaches > Build a marine food web

Organism cards (large)

     10 ? 2007-2009 The University of Waikato

    www.sciencelearn.org.nz

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