examples of food webs

LW2015 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. LW2015 d) Food webs are made up of lots of different food chains. Use the food web below to answer the following questions: Seagull Crab Starfish Mussel Rock Cod Sea Anemone Chiton Shrimp Seaweed Plant Plankton i) ii) What does a crab eat? ____________________ 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. LW2015 Rocky shore food web – Teacher information Living world - Objective 4 - Level 4 - Processing & interpreting Description Task: Students answer questions about feeding relationships in a rocky shore ecosystem. Assessment focus: interpreting a food web. Keywords Interdependence; food chain; food web; rocky shore. Answers/responses Y8 (10/05) a) The plankton is eaten by the mussel and the mussel is eaten by the seagull. or 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 receiver of energy, i.e., the one who is doing the eating.) or Who eats what. or What is eaten by what. c) Examples of food chains from the information given include Seaweed Plant plankton paua pupu koura fish sea bird easy easy 3 step food chain – easy 4 step food chain – moderate 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 ii) Starfish and Sea Anemone iii) Seaweed and Plant Plankton iv) Any one of: Seaweed or Plant plankton or Seaweed very easy 1 correct – easy 2 correct – moderate 1 correct – easy 2 correct – moderate difficult chiton shrimp shrimp shrimp sea anemone sea anemone sea anemone easy v) This food chain should be shown on the food web with arrows as below. Trial number 152 students LW2015 Seagull Crab Starfish Whelk Rock Cod Chiton Shrimp Cats eye Seaweed Plant Plankton Sea Anemone Mussel 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 http://ecomisconceptions.binghamton.edu/ for a summary of research of students' alternative ideas about ecosystems. NZCER research:  Common alternative ideas LW2015 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. LW2048 LW2046 LW2039 LW2038 LW2015 LW2004 LW2000 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.