Living Together

Overview

This is lesson 4 of 6 in Exploring Ecosystems Together. Students build on earlier learning about organisms, habitats, food webs and interdependence by identifying three types of close relationship: mutualism, commensalism and parasitism. They use real-world examples to create and explain a visual comparison chart.

Learning intentions

• We are learning to describe relationships between organisms.
• We are learning to distinguish mutualism, commensalism and parasitism.
• We are learning to use evidence from examples to classify relationships.
• We are learning to represent scientific ideas clearly in a visual chart.

Success criteria

• I can explain what mutualism, commensalism and parasitism mean.
• I can identify how each organism is affected in an example.
• I can correctly classify unfamiliar examples and explain my reasoning.
• I can create a clear chart using labels, examples and simple explanations.

Curriculum links

• Biological Science — Relationships in an ecosystem: describing different relationships between organisms, including mutualism and parasitism.
• Biological Science — Relationships in an ecosystem: applying ecosystem concepts to known and unknown examples to identify interdependence.
• Biological Science — Ecosystems: representing relationships between organisms using diagrams and food webs.
• Science capabilities and competencies: interpreting evidence, communicating explanations, and participating collaboratively in scientific discussion.

Lesson structure (45 minutes)

1. 0–5 min · Hook and recall. Teacher opens with the opening image and mystery question showing a bee on a flower and asks, “Are these organisms helping each other, harming each other, or simply sharing the same space?” Students discuss with a partner, then recall what interdependence means and share one food-web relationship from the previous lesson.

2. 5–13 min · Direct teaching. Teacher uses the relationship definitions and examples to introduce the idea that organisms may have close relationships over time. Model the three categories:

• Mutualism: both organisms benefit, such as bees receiving nectar while pollinating flowers.
• Commensalism: one organism benefits and the other is not significantly helped or harmed, such as barnacles gaining transport and access to food while a whale is generally unaffected.
• Parasitism: one organism benefits while the other is harmed, such as a flea gaining food from a dog. Students record the effect on each organism using the symbols +, 0 and −, and ask clarifying questions. Emphasise that the arrow of benefit or harm must be supported by the example.

3. 13–20 min · Guided classification. Teacher displays three new scenarios from the guided classification prompts and thinks aloud through the first one: “Who benefits? Who is harmed or unaffected?” Students use mini-whiteboards or fingers to show the relationship type, then justify one answer with a sentence such as, “This is parasitism because…”. Address the common misconception that every relationship in an ecosystem is competition or predation.

4. 20–32 min · Collaborative investigation. Teacher places students in 10 groups of three and distributes the Food Web Interaction Cards. Explain that groups should select or match examples connected to mutualism, commensalism and parasitism, then discuss the effect on each organism. Students take roles as reader, evidence checker and recorder; they must agree on a classification and prepare one spoken explanation. Circulate and ask, “What evidence shows that one organism benefits?” and “What happens to the other organism?”

5. 32–40 min · Visual chart creation. Teacher distributes the symbiotic relationships visual chart and uses the chart instructions and success checklist to model one completed row. Students individually create a three-part chart including each definition, the +/0/− effect on both organisms, one named example and a small labelled drawing or symbol. Students may use an example from their group discussion, but must explain it in their own words.

6. 40–45 min · Share and exit check. Teacher invites two or three students to share contrasting examples and uses the plenary comparison and exit question to revisit the three categories. Students complete the worksheet exit question: “A bird builds its nest in a tree; the bird gains shelter and the tree is not significantly affected. What relationship is this? Explain your answer.” Collect charts to identify next steps for lesson 5.

Resources

• the complete ecosystem relationships slide deck
• the symbiotic relationships visual chart
• the Food Web Interaction Cards
• Mini-whiteboards or scrap paper
• Pens, pencils and coloured pencils
• Projector or interactive display
• Group role cards or role labels
• Timer

Assessment

• Listen to partner and group explanations, checking whether students identify who benefits, who is unaffected and who is harmed.
• Use mini-whiteboard responses and questioning during guided classification to correct confusion between mutualism, commensalism and parasitism.
• Assess the visual chart and exit question for accurate definitions, classification, evidence and clear communication.

Differentiation

• Provide a word bank containing benefits, unaffected, harmed, mutualism, commensalism and parasitism, plus the sentence frames: “The ___ benefits because…” and “The ___ is ___ because…”.
• Pre-teach the +, 0 and − symbols and provide a partially completed chart for students who need reduced writing demand.
• Pair EAL learners with supportive peers and use the photographs, gestures and labelled diagrams in the slides; accept oral explanations before students record them.
• Extend confident students by asking them to classify an unfamiliar example, identify evidence that could be uncertain, and explain why relationships can depend on context.