examples of food webs

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                                 Rocky shore food web
                    This task is about interpreting food chains and food webs.

     All living things rely on the environment they live in for their basic needs, including food.
     Scientists use food chains and food webs to show feeding relationships.

a)   Here is an example of a food chain at the rocky shore.

                          Plant plankton             Mussel            Seagull

     Write the feeding relationship shown in this food chain in a sentence.



b)   What do the arrows in a food chain show?



c)   Use the information below or your own background knowledge to show two different food chains
     at the rocky shore.

            Plant plankton and various sorts of seaweed both live at the rocky shore.
            Paua, pupu and kina (sea eggs) are shellfish that “graze” on plants.
            Octopus (wheke) and seabirds eat fish and shellfish.
            Koura (crayfish) and fish eat shellfish.
            Kuku are shellfish that feed by filtering tiny plant plankton from the water.
d)   Food webs are made up of lots of different food chains.
     Use the food web below to answer the following questions:




                              Rock Cod
                                                           Sea Anemone

            Chiton                        Shrimp

                                         Seaweed                      Plant Plankton

     i)    What does a crab eat? ____________________

     ii)   What eats rock cod? ________________________________________________________

     iii) Name two producers. ____________________ and ____________________

     iv)   Shrimp are in three different food chains in the food web above. Show one of these
           food chains in the box below.

     v)    Here is another food chain.

                           Seaweed           Catseye        Whelk          Seagull

           Add this food chain into the food web at the top of the page.

              Rocky shore food web – Teacher information
                         Living world - Objective 4 - Level 4 - Processing & interpreting
Task: Students answer questions about feeding relationships in a rocky shore ecosystem. Assessment
focus: interpreting a food web.
Interdependence; food chain; food web; rocky shore.


                                                                                                 Y8 (10/05)
a) The plankton is eaten by the mussel and the mussel is eaten by the                   easy
   The seagull eats the mussel and the mussel eats plankton.
b) The transfer of energy. (The arrow in a food chain always points to the              easy
   receiver of energy, i.e., the one who is doing the eating.)
   Who eats what.
   What is eaten by what.
c) Examples of food chains from the information given include
   Seaweed           paua           koura                                               3 step food chain – easy
   Plant plankton           pupu            fish        sea bird                        4 step food chain –
   N.B. Students may have also included a food chain based on their own
   background knowledge. Check that it starts with a producer (plant) and
   that the arrows are moving in the right direction. In the trials all food
   chains had to start with a producer to be marked as correct.
d) i) Chiton                                                                            very easy

   ii) Starfish and Sea Anemone                                                         1 correct – easy
                                                                                        2 correct – moderate
   iii) Seaweed and Plant Plankton                                                      1 correct – easy
                                                                                        2 correct – moderate
   iv) Any one of:                                                                      difficult
       Seaweed             chiton           shrimp          sea anemone
        Plant plankton           shrimp            sea anemone
        Seaweed           shrimp            sea anemone                                 easy

   v) This food chain should be shown on the food web with arrows as
                                                                                            Trial number 152 students




                                                                Whelk          Mussel
                            Cod                      Sea Anemone

            Chiton                    Shrimp
                                                                Cats eye

                                    Seaweed                       Plant Plankton

Teaching and learning
Diagnostic and formative information
For question b) student responses showed developing ideas about food chains:
 Only 2 students discussed the transfer/flow of energy in their answers. All other students said that
   a food chain shows "what eats what", demonstrating a first step in developing the concept that
   food chains involve the flow or transfer of energy.
For question c) a common error was:
 Students not always starting their food chain with seaweed or plant plankton. Most students used
   all the animals in the correct order in their food chains.
For questions d) i) & ii) a common error was:
 Confusion reading the direction of arrows in a food chain, so that a number of students showed a
   crab eats a seagull and a chiton eats a rock cod.
For question d) iii) & iv) common errors were:
 Lack of background knowledge of the word 'producers' so that students chose some of the
   consumers rather than the 2 producers (seaweed and plant plankton).
 Confusion with the direction of arrows.
 Food chain did not start with a producer.

Links to research
Research shows that common misconceptions about ecosystems, food chains and food webs include:
 organisms higher in the food chain eat everything below them;
 food chains involve predators and prey and no producers; and
 food webs are interpreted as simple food chains.
Go to for a summary of research of students' alternative
ideas about ecosystems.
NZCER research:
 Common alternative ideas
Next steps
Nature of science – representing a food chain
Science has its own particular language and ways of expressing ideas. Food chains, with their arrows
showing the transfer of energy to the consumer, are an example of this. If students have difficulty with
the correct direction of the arrows in a food chain, discuss how the arrows show the direction of
energy flow. Discussion could include providing the prompt "goes into" to help with the
understanding that food chains represent the passing on/flow/transfer of energy.

Other resources
The following Level 4 assessment resource items can be used to support and scaffold students in their
understanding of food chains and food webs.
Ministry of Education (2003). Building Science Concepts Book 21, Life between the tides,
Wellington: Learning media.
Ministry of Education (2003). Building Science Concepts Book 22, Tidal Communities. Wellington:
Learning media.
Ministry of Education (1999). Making Better Sense of the Living World, Who eats Whom?, Activity
14, Page 115.