1. Energy Flow Through Ecosystems

2. Organisms are classified according to how they obtain energy
Autotroph: organism that obtains energy from sunlight (photoautotroph) or from chemical compounds (chemoautotroph)
Examples:
green plants photosynthesize
archaebacteria near deep sea vents get their energy through chemical reactions using methane or sulfur compounds

3. Organisms are classified according to how they obtain energy
Heterotroph: organism that obtains its energy by consuming other organisms
Example:
Animals undergo cellular respiration

4. Types of Heterotrophs Herbivore – eats plants Carnivore – eats meat
Omnivore – eats both meat and plants
Scavenger – eats carcasses of dead organisms (vulture, opossum)
Detritivore – eats fragments of dead matter (detritus) to return the nutrients back to the ecosystem (earthworm, millipede, fiddler crab)
Decomposer – breaks down dead organisms using external digestion (bacteria, fungi)

5. Energy Flow Models
Food Chain - Simple model that shows the flow of energy through an ecosystem
Arrows show direction of energy flow

7. Energy Flow Models
Food Web – Complex model that shows the many food chains and pathways through which energy can flow through an ecosystem
Arrows always
show direction
of energy flow

8. Trophic Levels
Each step in a food web or food chain is a trophic level
Trophic level = “feeding” level
1st trophic level = producers
2nd trophic level = primary (1°) consumers
3rd trophic level = secondary (2°) consumers
4th trophic level = tertiary (3°) consumers
5th trophic level = quaternary (4°) consumers

9. Trophic Levels 5th Trophic Level 4th Trophic Level 3rd Trophic Level
2nd Trophic Level
1st Trophic Level

10. Trophic Levels Tertiary (3°) Consumers Secondary (2°) Consumers
Primary (1°) Consumers
Producers

11. Energy Pyramids

12. Energy Pyramids Tell us 4 things about each trophic level:
Amount of energy available
10% law – on average, 10% of the energy from one trophic level is transferred to the next highest trophic level (gets stored as flesh)
the remaining energy (90% of the original energy in the previous trophic level) is lost to metabolic processes and heat
Organism’s niche
producer, primary consumer, etc.
Amount of biomass
total mass of living matter (e.g., grams of grass)
Population size
number of individuals (e.g., 1,000,000 blades of grass)

13. Energy Pyramid

14. Energy Pyramids

15. Create your own energy pyramid
Only 3 trophic levels
For each trophic level write
Name of the organism
Its niche (producer, primary consumer, etc)
Relative amount of energy available at that level (assume 1st trophic level = 100%)
The trophic level

16. 3rd Trophic Level
2nd Trophic Level
1st Trophic Level