Revision sheet: Ecosystem Biology and Sustainability

Ecosystems Revision Sheet

1. 📌 Essentials

• An ecosystem comprises biotic (living) and abiotic (non-living) components interacting within Earth's biosphere.
• Photosynthesis converts solar energy chemical energy; cellular respiration releases it.
• Food chains show linear energy transfer; food webs depict complex feeding relationships. Energy transfer efficiency between trophic levels is approximately 10%.
• Key biogeochemical cycles: water, carbon, nitrogen; human activities disrupt these cycles.
• Limiting factors (resources, predation, competition) regulate population sizes.
• Biodiversity (species richness) is vital for ecosystem stability; loss leads to extinction.
• Greenhouse gases (CO₂, CH₄, N₂O) trap heat, contributing to climate change.
• Earth's layers: core (hotter), mantle, crust; atomic number = protons.
• Earth's rotation (24h) causes day/night; revolution (365 days) causes seasons.
• Tides result from Moon's gravitational pull.

2. 🧩 Key Structures & Components

• Atmosphere — gaseous layer supporting respiration and climate regulation.
• Lithosphere — Earth's crust and upper mantle; habitat for terrestrial life.
• Hydrosphere — all water bodies; involved in water cycle.
• Biosphere — all living organisms interacting with other spheres.
• Producers — autotrophs (plants, algae) that synthesize organic molecules.
• Consumers — heterotrophs; primary (herbivores), secondary, tertiary.
• Decomposers — fungi, bacteria breaking down organic matter.
• Biogeochemical Cycles — pathways for elements like water, carbon, nitrogen.
• Sun — primary energy source driving photosynthesis.
• Greenhouse Gases — CO₂, CH₄, N₂O influencing Earth's temperature.

3. 🔬 Functions, Mechanisms & Relationships

• Photosynthesis captures solar energy, producing glucose and oxygen.
• Cellular respiration breaks down glucose, releasing energy for cellular activities.
• Food webs integrate multiple food chains, illustrating complex energy flow.
• Energy diminishes (~90%) at each trophic level; only ~10% transferred.
• Water cycle involves evaporation, condensation, precipitation, transpiration.
• Carbon cycle: photosynthesis (carbon sink), respiration, combustion (carbon source).
• Nitrogen fixation by bacteria converts N₂ into ammonia, enabling plant uptake.
• Limiting factors restrict population growth; ecosystems have a carrying capacity.
• Human activities (pollution, deforestation) disrupt cycles and threaten biodiversity.
• Ecosystem services: provisioning (resources), regulating (climate), cultural (recreation).

4. 📊 Comparative Table

Item	Key Features	Notes / Differences
Photosynthesis	Converts light energy to chemical energy in glucose	6CO₂ + 6H₂O + light → C₆H₁₂O₆ + 6O₂
Cellular respiration	Releases energy from glucose	C₆H₁₂O₆ + 6O₂ → 6CO₂ + 6H₂O + energy
Food chain	Linear energy transfer	Producer → Primary → Secondary → Tertiary
Food web	Interconnected feeding relationships	More complex than chains
Water cycle	Evaporation, condensation, precipitation, transpiration	Continuous water movement
Carbon cycle	Photosynthesis, respiration, combustion	Maintains atmospheric CO₂ levels
Nitrogen cycle	Fixation, nitrification, denitrification	Essential for amino acids, proteins
Greenhouse gases	CO₂ (~76%), CH₄ (~16%), N₂O (~6%)	Major contributors to global warming

5. 🗂️ Hierarchical Diagram

Earth & Ecosystems
 ├─ Support Systems
 │    ├─ Atmosphere
 │    ├─ Lithosphere
 │    ├─ Hydrosphere
 │    └─ Biosphere
 ├─ Energy & Cycles
 │    ├─ Photosynthesis
 │    ├─ Cellular Respiration
 │    ├─ Water Cycle
 │    ├─ Carbon Cycle
 │    └─ Nitrogen Cycle
 ├─ Food Webs & Energy
 │    ├─ Food Chain
 │    ├─ Food Web
 │    └─ Energy Transfer
 ├─ Ecosystem Influences
 │    ├─ Limiting Factors
 │    ├─ Carrying Capacity
 │    └─ Human Impact
 └─ Threats & Solutions
      ├─ Habitat Loss
      ├─ Pests & Pesticides
      ├─ Pollution
      ├─ Invasive Species
      └─ Climate Change

6. ⚠️ High-Yield Pitfalls & Confusions

• Confusing food chain with food web; web is more complex.
• Mistaking photosynthesis for cellular respiration; opposite processes.
• Overestimating energy transfer efficiency; it's approximately 10%, not 100%.
• Ignoring human impacts on biogeochemical cycles.
• Assuming all greenhouse gases have equal warming potential.
• Confusing Earth's layers; core is hottest, but not visible.
• Misunderstanding the cause of seasons; Earth's tilt, not distance from Sun.
• Overlooking the role of decomposers in nutrient cycling.
• Mistaking the atomic number for atomic mass.

7. ✅ Final Exam Checklist

• Define and explain the components of Earth's biosphere.
• Describe the process of photosynthesis and its chemical equation.
• Differentiate between food chain and food web.
• Explain energy transfer efficiency in trophic levels.
• Outline the water, carbon, and nitrogen cycles.
• Identify the roles of producers, consumers, and decomposers.
• Understand the impact of human activities on ecosystems.
• Describe the effects of greenhouse gases and climate change.
• Recall Earth's layers and their characteristics.
• Know the basic atomic structure and periodic table trends.
• Apply Ohm's Law and circuit principles.
• Explain causes of day/night and seasonal changes.
• Describe lunar and solar eclipses, and tides.
• Recognize common ecological threats and conservation strategies.
• Understand the importance of biodiversity and ecosystem services.

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