Our Environment: Ecology & Ecosystems
The complex web of biotic and abiotic factors and energy pathways.
An ecosystem consists of biotic components (producers, consumers, decomposers) and abiotic components (temperature, soil, water) interacting as a functional unit. Flow of energy is unidirectional.
Energy enters ecosystems through primary producers (plants) via solar capture and is transferred up successive trophic levels. The chemical accumulation of non-biodegradable toxins increases at higher trophic levels.
Key Takeaways
- •Energy flow is unidirectional: from sun to producers, and then up consumers, never in reverse.
- •Only a small fraction of energy is passed to the next trophic level (Lindeman's 10% Law).
- •Biomagnification causes top predators to accumulate the highest concentrations of non-biodegradable pesticides.
Core Concepts & Definitions
1Trophic Levels and 10% Energy Transfer
A food chain represents the linear sequence of organisms transferring energy. Each step in a food chain is a trophic level: Producers -> Primary Consumers -> Secondary Consumers -> Tertiary Consumers.
•Because energy is lost as metabolic heat, food chains rarely exceed 4-5 trophic levels.
•[INSERT: Ecological pyramid of energy showing decreasing values at higher levels]
Quick Revision Notes
- •Always verify units and maintain coordinate systems.
- •Check boundary conditions and reference variables before applying formulas.
- •Ensure decimal precision is correct on output results.
Equations & Calculation Methods
Lindeman's 10% Energy Law
States that only about 10% of the organic energy from one trophic level is incorporated into the biomass of the next level.
Step-by-Step Worked Examples
Calculating Energy Transfer
Problem: If green plants capture 20,000 Joules of solar energy, how much energy will be available to a snake (tertiary consumer) in the food chain: Plants -> Grasshopper -> Frog -> Snake?
Step-by-step Solution:
- 1Solar energy captured by plants = 20,000 J.
- 2Plants (Producers): 1% of solar energy is absorbed = 200 J.
- 3Grasshopper (Primary Consumer): Receives 10% of 200 J = 20 J.
- 4Frog (Secondary Consumer): Receives 10% of 20 J = 2 J.
- 5Snake (Tertiary Consumer): Receives 10% of 2 J = 0.2 Joules.
Topic FAQ
Decomposers (like bacteria and fungi) break down dead organic matter and waste, recycling nutrients back into the soil for reuse by plants.
Related Topics
Lab Experiment: Building a Sealed Ecological Terrarium
Required Materials
- Clean 2L glass jar with airtight lid
- Pebbles and activated charcoal
- Potting soil
- Small slow-growing plants
- Water mist spray
Procedure Steps
- 1Add a 2 cm layer of pebbles at the bottom for drainage, followed by a thin layer of charcoal.
- 2Add potting soil on top, creating a bed about 5-6 cm deep.
- 3Carefully plant small seedlings (like mosses, ferns) and water them lightly with a mist spray.
- 4Seal the jar tightly and place it in indirect sunlight.
- 5Observe the terrarium weekly to check for condensation and plant growth without adding fresh water.
Practice Quiz & Interactive Assessment
Syllabus Review Mode
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Printable Worksheet: Ecological Ratios and Environmental Stewardship
Classroom Homework Questions
- Q1.Explain biological magnification with an example of an aquatic food chain.
- Q2.State Lindeman's 10% law of energy transfer and explain why food chains are limited in length.
- Q3.What is the ozone layer? Why is its depletion a cause for concern?
- Q4.Suggest three actionable methods to minimize waste generation at home.
Frequently Asked Questions
Decomposers (like bacteria and fungi) break down dead organic matter and waste, recycling nutrients back into the soil for reuse by plants.