Rocky shore food web

Rocky shore food web

Pencil and paper
Overview
Connecting to the Curriculum
Marking Student Responses
Working with Students
Further Resources
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.
Pāua, 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:
 
  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.
 
Level:
4
Curriculum info: 
Science, Communicating in science, Living World
Keywords: 
ecology, interdependence, food chains, food webs, diagrams, rocky shore
Description of task: 
Task: Students answer questions about feeding relationships in a rocky shore ecosystem. Assessment focus: interpreting a food web.
Curriculum Links: 
Science capabilities
The capabilities focus is brought about by the conversations you have and the questions you ask.
 
Capability: Interpret representations
This resource provides opportunities to discuss scientific conventions for representing feeding relationships (a food web).
 
 
 

 
Science capabilities: 
Interpret representations
Making Better Sense: 
Food Chains
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.		 easy
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.		 easy
c) Examples of food chains from the information given include:

Seaweed  pāua  koura
Plant plankton  pupu  fish   sea bird

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.
3 step food chain – easy 
4 step food chain – moderate
d) i)
ii)
iii)
iv)		 Chiton
Starfish and Sea Anemone
Seaweed and Plant Plankton
Any one of:

Seaweed  chiton  shrimp  sea anemone

or

Plant plankton  shrimp  sea anemone

or

Seaweed  shrimp  sea anemone
very easy
1 correct  – easy
2 correct – moderate
1 correct – easy
2 correct – moderate
difficult
  v) This food chain should be shown on the food web with arrows as below. easy

Trial number 152 students.

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

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. 
  • 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.