in food web diagrams that are not intuitive for nonexpert readers. As
discussed later, the arrows indicate a direct relationship between adjacent organisms. They do not mean (as Mitchell thought) that all the
food accumulates with the animal at the end.
Example 5: Apparently Correct Interpretation
RESEARCHER: Can you tell me what’s happening in this diagram, please?
JOHN: It show plants get eaten by butterflies and snails, which get eaten
by frogs, which get eaten by birds.
RESEARCHER: Excellent, and what do the arrows mean?
JOHN: It means that that’s showing what that particular thing, it gets
John started at the plant (left-hand side), reading confidently and
fluently from beginning to end. He interpreted the arrows by
using the meaning “is eaten by,” which suggested possible prior
learning. John had no difficulty interpreting the diagram and read
it succinctly. He correctly interpreted arrow meaning and consistently read the diagram in the desired direction. Despite this
John’s diagram reading did not help him to construct a complete,
scientifically accurate explanation. John (like others) read the diagram on a superficial level, focusing on food acquisition and overlooking the critical purpose of energy transfer. He also failed to
distinguish the two food chains making up the food web. Only
one student in the study considered the interlinked food chains
The analysis of the example students’ interview dialogues provides
evidence that elementary-level students experienced a range of difficulties in reading the food web diagram. In general their sense-making comprised surface-level understanding of the underlying
ecological concepts. Findings from this study provide vital background for secondary teachers commencing teaching about these
Five trends in students’ sense-making from food webs worthy of
consideration by secondary teachers are starting point, reading pathway, arrow meaning, repeat exposure, and depth of diagram processing. Each has relevance for biology teachers in devising instructional
strategies to challenge existing preconceptions, to guide students in
deeper processing of food web diagrams, and to extend student’s
understanding of ecological concepts.
Where to Start Reading
Three starting points, the bird (right), the butterfly / snail (second left)
and the plant (left) were recorded in my study indicating students
were unclear about where to commence reading the food web diagram. Teachers should not assume students will automatically read
left-right following normal conventions for text. Food webs are
designed to be read with a predetermined start, at the producer. Secondary students may require specific instruction on this non-arbitrary
starting point. Students need to learn food webs always start with the
producer(s) regardless of position on the page. (Food webs are traditionally drawn with producers at the bottom and consumers in order
of trophic level above).
Prior knowledge (what animals eat) and subconscious intuitions
(for example, largest animal is most important) can affect where student attention is initially directed on the diagram. In a classroom
asking students where they think a food web starts and discussing
differing ideas would be a useful instructional strategy. Identifying
the plant as the initiator of a food web is critical for students to
appreciate its role as a producer. The unique ability of producers
to assimilate Sun’s energy means animals ultimately depend on them
for energy. This knowledge helps students understand the purposes
of food webs as a model to think about habitats by showing possible
feeding relationships and an ecological tool (Kitchen, 2008, p. 32) to
map energy (and matter) flow in ecosystems.
Reading Pathway Through the Diagram
Students used a variety of reading pathways to navigate their way
through the diagram. Three trends in reading direction were
observed: right to left, left to right, and convoluted, back and forth
in different directions. Food webs are designed to be read in a particular sequence, usually left to right for linear presentations or bottom
Figure 5. Elaine’s new reading path.