1. Energy Flow in Ecosystems (LT 1.6)

2. This lecture will help you understand
Feeding relationships
Food Webs
Trophic levels
Energy flow
Productivity
….. Ecology & the ecosystem

3. All the parts of an ecosystem are interrelated.
Biotic (living): trees, animals, insects, bacteria
& abiotic (nonliving): sunlight, temperature, soil, water, pH, nutrients
Highly dependent on climate.
Boundaries are important because they help distinguish ecosystems.
Knowing boundaries help us identify components and trace energy/matter cycles.

4. Ecosystems interact with each other by exchanging energy and matter.
Energy flows through ecosystems.
Solar energy enters through plants
Spreads to producers (autotrophs) & consumers (heterotrophs).
2nd law of thermodynamics says energy conversion is not 100% efficient –not all energy is transferred to consumer, some is lost as heat.

6. Food Chain vs. Food Web – What do the arrows show us?

7. Trophic levels: organism’s role/place/order in the food chain
Food chain vs food web:
Food chain: what eats what – producers to tertiary consumers
Food web: a bunch of food chains interacting

8. Heterotrophs = consumers
Primary consumers – eat producers
Secondary consumers – eat primary consumers
tertiary consumers – eat secondary consumers
Scavengers: carnivores that eat dead animals
Detritivores: break down detritus (dead tissue/waste) into smaller particles – responsible for cycling matter
Decomposers: Break down the particles from detritivores

9. Laws of Thermodynamics
1st Law: Energy cannot be created nor destroyed, only transformed.
2nd Law: When energy is transformed, it loses quality.

10. Nearly all energy that powers ecosystems is solar energy, a form of kinetic energy.
Producers (autotrophs) use sun’s energy to produce usable forms of energy through photosynthesis.

12. Cellular respiration = unlocks chemical energy stored in food sources (like glucose).
All organisms perform cellular respiration.

13. The amount of energy available determines how much life can be supported.
Gross Primary Productivity (GPP): total amount of solar energy captured by producers
Net Primary Productivity (NPP): energy captured minus energy respired
NPP = GPP – respiration by producers
Determine the rate of photosynthesis by: measuring the compounds that participate in the reaction (example: CO2)
NPP efficiency ranges from 25% to 50% of GPP. *measure NPP is a. useful way to compare ecosystem productivity

14. Biomass: total mass of all living matter in an area
Rate of production determined by NPP
Standing crop: amount of biomass present at a particular time
Ecological efficiency: Proportion of consumed energy that can be passed up the trophic levels (5-20%)
What is the 10% Rule? Only 10% of biomass can be passed up to the next level. For example, producers get 100J of energy, primary consumers would only get 10J.

15. Trophic pyramid: diagram to represent the distribution of biomass (using the 10% rule)