Ecosystems | Substitute Teacher
Students analyze how biotic and abiotic factors interact in ecosystems, trace energy flow through food webs, and evaluate how disturbances affect ecosystem stability. This substitute-friendly lesson uses structured reading, diagram analysis, discussion, and a short written response to keep a Grade 12 STEM class engaged and accountable for 90 minutes.
| Term | Definition |
|---|---|
| Ecosystem | A community of organisms and the physical environment they interact with. |
| Biotic factor | A living part of an ecosystem, such as plants, animals, fungi, or bacteria. |
| Abiotic factor | A nonliving part of an ecosystem, such as sunlight, water, soil, or temperature. |
| Producer | An organism that makes its own food, usually through photosynthesis. |
| Consumer | An organism that gets energy by eating other organisms. |
| Decomposer | An organism that breaks down dead matter and recycles nutrients. |
| Food web | A network of connected food chains showing energy transfer in an ecosystem. |
| Trophic level | A feeding position in a food chain or food web. |
| Resilience | The ability of an ecosystem to recover after a disturbance. |
Display two prompts: 'What makes an ecosystem stable?' and 'Name one biotic and one abiotic factor in a local ecosystem.' Circulate and monitor completion.
Individually write responses in notebooks. Share one idea with a partner when finished.
Review ecosystem components, energy flow, and vocabulary using the board or slides. Use a simple food chain to model energy transfer and clarify producer-consumer-decomposer roles.
Take notes, answer cold-call questions, and label a sample diagram with the teacher.
Distribute a food web diagram. Model one example of how removing a species affects the system, then assign students to answer 3-4 analysis questions.
Work in pairs to trace arrows, identify trophic levels, and predict effects of a population decrease or increase.
Provide a short reading or case study about a forest, grassland, or aquatic ecosystem affected by drought, invasive species, or pollution. Check for understanding and clarify as needed.
Annotate the text for causes, effects, and evidence. Answer guiding questions in writing.
Give each group a different scenario, such as removal of a keystone species or a drought year. Instruct students to create a brief cause-effect explanation.
Collaborate to create a 3-step explanation showing how the disturbance changes populations and ecosystem stability.
Prompt students to write a short claim-evidence-reasoning response: 'How do ecosystems maintain stability, and what can disrupt it?'
Write an individual paragraph using vocabulary and evidence from the lesson.
Ask a few volunteers to share responses and summarize the day’s key ideas: interactions, energy flow, and resilience.
Listen, contribute one takeaway, and prepare for dismissal.
Reinforce that ecosystems are dynamic systems shaped by interactions among living and nonliving factors. Emphasize that energy flows through trophic levels, and changes to one part of the system can affect many others.
Write a one-page reflection explaining how one disturbance, such as drought, invasive species, or pollution, can affect an ecosystem. Include at least three vocabulary terms and one real-world example.