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:
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.
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
Cod Sea Anemone
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 http://ecomisconceptions.binghamton.edu/ for a summary of research of students' alternative
ideas about ecosystems.
Common alternative ideas
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.
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:
Ministry of Education (1999). Making Better Sense of the Living World, Who eats Whom?, Activity
14, Page 115.