Understanding Symbiosis

Overview

Subject: Science (Biology)
Year Level: Year 13
Lesson Duration: 70 minutes
Curriculum Alignment: NCEA Level 3, Achievement Standard 91603 - Demonstrate understanding of how an animal maintains a stable internal environment and how this is influenced by environmental factors.

Learning Objectives

By the end of the lesson, students will:

• Define and explain symbiosis, mutualism, and commensalism.
• Identify real-life examples of biotic interactions in nature.
• Analyse how symbiotic relationships benefit or impact species.
• Develop observational skills by identifying mutualistic and commensal organisms in their environment.

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Lesson Structure

1. Introduction (10 minutes)

Objective: Provide students with a fundamental understanding of biotic interactions, setting the stage for exploration.

• Greet students and introduce the topic: "Today, we will explore how species interact in ways that benefit at least one of them. Some of these interactions are essential for survival!"
• Using slides, define Biotic Interactions as relationships between two different living organisms.
• Introduce key terms:
  • Symbiosis – A close ecological relationship between two species.
  • Mutualism – Both species benefit.
  • Commensalism – One species benefits while the other is neither helped nor harmed.
• Use visual aids with examples such as clownfish and anemones, cleaner fish and larger fish, orchids on trees, and epiphytic plants.
• Encourage students to share other examples they know.

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2. Outdoor Exploration (30 minutes)

Objective: Enable hands-on learning by observing real-life examples of biological interactions in the natural environment.

Activity 1 – Finding Mutualism: Lichens

• Take students outside to an area where lichens grow on rocks or tree trunks.
• Ask guiding questions:
  • "What two organisms might be forming this lichen?"
  • "How might each partner benefit?"
• Explain the relationship: Lichens are made up of fungi and algae. The fungus provides structure and water absorption, while the algae photosynthesise to produce food.
• Have students sketch or take notes on lichen structure.

Activity 2 – Observing Commensalism: Epiphytes

• Locate epiphytic plants (e.g., orchids or mosses) growing on tree branches.
• Ask students:
  • "Who is benefiting in this interaction?"
  • "Is the tree harmed in any way?"
• Explain that epiphytes gain space, sunlight, and nutrients from trapped debris, but the tree is unaffected, demonstrating commensalism.

Discussion Outdoors (5 minutes)

• Gather students to reflect on their observations:
  • "Which interaction surprised you the most?"
  • "Why do you think these relationships have evolved?"
• Students briefly discuss in pairs and share thoughts with the class.

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3. Classroom Reflection & Summary (25 minutes)

Objective: Consolidate learning by reinforcing key concepts with slides and group discussions.

Review Discussion (10 minutes)

• Display an image of a parasitic interaction (e.g., mistletoe on a tree) and ask:
  • "How is this different from mutualism and commensalism?"
• Guide students in categorising different relationships into correct symbiotic types.

Exit Ticket Activity (10 minutes)

Each student writes on a sticky note:

1. An example of mutualism or commensalism from today’s lesson.
2. A real-world example of symbiosis they’ve heard about.
3. Any lingering questions.

• Stick these to the board for a class discussion.

Closing Reflection (5 minutes)

• Show a slide summarising mutualism and commensalism.
• Ask, "Why are these interactions important in an ecosystem?"
• Highlight how symbiotic relationships contribute to biodiversity.
• Assign a short research task: Students find and bring in an example of symbiosis from New Zealand flora/fauna for next class (e.g., tui and harakeke, native mycorrhizal fungi).

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Assessment & Extension

Formative Assessment:

• Participation in observations and discussion.
• Exit ticket responses.

Extensions:

• Research NZ species with symbiotic relationships.
• Explore human applications of mutualism (e.g., gut microbiomes).

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Teacher Notes

• Preparation: Scout outdoor teaching locations beforehand.
• Materials: Printed slides, clipboards, pens, sticky notes.
• Differentiation: Provide visual cues and discussion support for students needing extra assistance.
• Risk Management: Ensure safety outdoors; remind students of respectful engagement with nature.

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This hands-on lesson brings scientific concepts to life while reinforcing critical thinking—showing students that real-world biology is happening all around them!