Ecosystems in Balance

Objective

Students will analyse the delicate balance within ecosystems, exploring energy flow, trophic levels, and human impact while aligning with Grade 10 California Next Generation Science Standards (NGSS) under LS2: Ecosystems: Interactions, Energy, and Dynamics.

Standards Addressed:

• HS-LS2-1: Use mathematical representations to support claims for patterns in the cycling of matter and flow of energy in an ecosystem.
• HS-LS2-6: Evaluate claims, evidence, and reasoning that stability of ecosystems is determined by changes in organisms or the physical environment.
• HS-LS2-7: Design, evaluate, and refine a solution for reducing human impact on the environment and biodiversity.

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Materials

• Projector and class visual aids (diagrams of food webs, energy pyramids)
• Printed role cards (detailing organisms and their roles in a food web)
• Large chart paper and markers (group work)
• Small whiteboards for formative assessments
• LEGO® or Jenga blocks (optional for modelling stability)
• Exit tickets with reflective questions

Lesson Structure (60 Minutes)

1. Warm-Up: Ecosystem Quickfire (5 minutes)

• Objective: Activate prior knowledge and energise the classroom.
• Pose a series of rapid-fire questions to the class:
  • What key roles do plants play in an ecosystem?
  • What happens if an apex predator disappears?
  • What might cause an ecosystem to collapse suddenly?
• Students record answers on their whiteboards and hold them up – discuss briefly.

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2. Concept Introduction: Energy Flow in Ecosystems (10 minutes)

• Objective: Understand the flow of energy through trophic levels.
• Visual Aid: Show a diagram of an energy pyramid (producers, primary consumers, secondary consumers, tertiary consumers).
• Discuss:
  • How energy decreases as it moves up the pyramid.
  • The "10% Rule" and why energy diminishes at higher levels.
  • Why ecosystems require producers to thrive.
• Engagement Activity: Students perform a quick “popcorn-style” brainstorm, identifying examples of organisms for each level.

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3. Interactive Group Activity: Build a Balanced Ecosystem (20 minutes)

• Objective: Explore ecosystem dynamics with hands-on learning.
• Split the class into six large groups (approx. 25 students per group). Each group will create and present its own food web using the following steps:

Instructions:

1. Role Assignment (5 minutes):

   • Provide each student in the group with a role card (e.g., Sun, Grass, Grasshopper, Frog, Hawk, Decomposer, etc.).
   • Cards include specific details about the organism's role in an ecosystem and its ecological niche.

2. Collaborative Web Building (8 minutes):

   • Students physically arrange themselves into a chain and construct a "spiderweb" illustration on chart paper, connecting organisms to represent energy flow among producers, consumers, and decomposers.
   • Annotate the web to highlight trophic levels, arrows showing energy flow, and key balances required for stability.

3. Debrief (7 minutes):

   • Each group performs a 2-minute summary presentation.
   • Pose “what if” scenarios: e.g., What if all decomposers were removed? or What happens if a trophic level collapses?

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4. Human Impact Exploration (10 minutes)

• Objective: Evaluate human influence on ecosystem stability.
• Scenario Discussion: Split students into pairs. Each pair will discuss specific examples of human impacts on ecosystems such as:
  • Deforestation
  • Overfishing
  • Pollution (plastic waste)
  • Introduction of invasive species

Challenge Question:

• Ask students to consider and brainstorm solutions to reduce the negative human impact on biodiversity and ecosystem dynamics. Each pair writes one solution on post-it notes to share during the final activity.

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5. Modelling Ecosystem Stability (10 minutes)

• Objective: Experience hands-on ecosystem dynamics.
• Activity:
  • Using LEGO® or Jenga blocks, students build tower models to represent ecosystem stability.
  • Removing blocks one by one simulates the loss of species or energy flow disruptions caused by environmental changes.
  • Lead reflection: “What do these blocks teach us about sustainability and balance?”

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6. Closing and Reflection (5 minutes)

• Exit Ticket:
  • Students answer reflective questions on a card:
    1. What surprised you most about how food chains work?
    2. What role does biodiversity play in ecosystem health?
    3. Name one action humans can take to support ecosystem stability.

Collect exit tickets as students leave.

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Differentiation

• For Advanced Learners: Include an additional task about biochemical cycles (water, carbon, nitrogen) and their links to energy flow.
• For Support Needs: Provide pre-drawn food web templates where struggling students can fill in blanks with organism names.
• Pair ELL students with bilingual partners to model discussion and scaffold vocabulary.

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Assessment

• Formative: Warm-up answers shared on whiteboards, observations of group discussion, annotated food web diagrams.
• Summative: Completion of exit tickets and group presentations.

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Extensions

For homework or extra credit, students can research a California ecosystem (e.g., kelp forest, desert, or redwood forest) and present a brief written or visual report on its biodiversity and human impact challenges.