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Unit 5: Ecology and Environment
Chapter 2: Ecosystem
Components of an Ecosystem
Abiotic (Non-living):
Temperature, light, water, soil, etc.
Biotic (Living):
Producers:
Autotrophs (e.g., plants).
Consumers:
Heterotrophs (herbivores, carnivores).
Decomposers:
Break down dead organic matter (e.g., bacteria, fungi).
Productivity
The rate of biomass production.
Gross Primary Productivity (GPP):
Total rate of photosynthesis.
Net Primary Productivity (NPP):
GPP minus the energy used by producers for respiration (R).
NPP = GPP - R
Secondary Productivity:
Rate of new organic matter formation by consumers.
Decomposition
Breakdown of dead organic matter (detritus) by decomposers.
Steps:
Fragmentation:
Breakdown by detritivores (e.g., earthworms).
Leaching:
Water-soluble nutrients seep into the soil.
Catabolism:
Enzymatic degradation.
Humification:
Formation of humus.
Mineralization:
Release of inorganic nutrients.
Energy Flow
Energy flows
unidirectionally
from the sun to producers to consumers.
Food Chain:
A linear sequence of energy transfer.
Grazing Food Chain (GFC):
Starts with producers.
Detritus Food Chain (DFC):
Starts with dead organic matter.
Food Web:
A network of interconnected food chains.
Trophic Levels & 10% Law
Trophic Level:
The position an organism occupies in a food chain.
10% Law:
Only about 10% of the energy from one trophic level is transferred to the next.
This limits the length of food chains.
Ecological Pyramids
Graphical representation of trophic levels.
Pyramid of Energy:
Always upright.
Pyramid of Number:
Can be upright, inverted, or spindle-shaped.
Pyramid of Biomass:
Can be upright (terrestrial) or inverted (aquatic).