3.8.1Additional lessons
Ecosystems as Open Systems — IB Biology SL Revision Notes & Topical Questions
5 min read 5 parts Lesson 91 of 142
Curriculum Equation Key قوانين الرقم الهيدروجيني والاتزان الأيوني - pH & Acid-Base Equilibrium FormulasFast Exam Solution
pH = -log[H⁺] | pOH = -log[OH⁻] | pH + pOH = 14 | [H⁺][OH⁻] = 10⁻¹⁴
Word Equation & Conditions: الرقم الهيدروجيني = -لوغاريتم تركيز أيون الهيدروجين | pH + pOH = 14
Location & Specifications: الاتزان الأيوني، كيمياء 3 ثانوي، التحصيلي، و AP Chemistry.
Part 1 of 5What Is an Ecosystem
Definition
- Definition An ecosystem is a community of organisms and their abiotic environment, with which they interact.
Scale
- Scale Ecosystems range from a rock pool to an ocean or forest.
Complexity
- Complexity A desert is a relatively simple ecosystem, but a tropical rainforest is very complex.
Abiotic factors
- Abiotic factors Light, temperature, water and mineral availability affect which organisms can live there.
Part 2 of 5Open and Closed Systems
Open system
- Open system Both energy and matter can enter and leave, which is true of natural ecosystems.
Closed system
- Closed system Energy can enter and leave, but matter is not exchanged and is recycled within the system.
Energy in
- Energy in Sunlight is captured by producers and becomes stored chemical energy in organic compounds.
Energy out
- Energy out Energy leaves as heat from respiration and when organisms or products are removed.
Matter in and out
- Matter in and out Matter enters by immigration, rainfall and mineral inputs and leaves by emigration, harvesting or leaching.
| Feature | Open | Closed |
|---|---|---|
| Energy exchange | Yes | Yes |
| Matter exchange | Yes | No |
| Example | A natural forest | A sealed bottle culture |
Part 3 of 5Sunlight as the Energy Source
Energy flows through ecosystems in one direction.
1
Most ecosystems depend on light energy from the Sun.
2
Producers use photosynthesis to convert light energy into chemical energy in carbohydrates.
3
This stored energy passes to consumers when producers are eaten.
4
At each stage some energy is released as heat, which cannot be reused by organisms.
5
Some ecosystems, such as deep-sea vents, depend on chemical energy from inorganic substances instead of sunlight.
Part 4 of 5Laws and Models
Laws and Models
Laws in science
- Laws in science Laws are generalised principles that describe what happens but do not explain why, unlike theories.
Conservation of energy
- Conservation of energy Energy is never created or destroyed, only converted from one form to another.
Heat
- Heat Energy transformations in organisms release heat to the surroundings.
Use
- Use Such laws help predict how energy moves through ecosystems.
Part 5 of 5Exam Checklist & Tips
3.8.1 – Key Points for the Exam
- Ecosystem A community and its abiotic environment.
- Open system A system that exchanges energy and matter with its surroundings.
- Closed system A system that exchanges energy but not matter.
- Producer An organism that makes its own organic compounds.
Common Mistakes
- Saying energy is recycled in an ecosystem; energy flows and is lost as heat, while matter is recycled.
- Calling a natural ecosystem a closed system.
- Thinking that sunlight is the energy source for every ecosystem.
- Writing that energy is destroyed when it is lost as heat.
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