1. 34.2 – Energy Flow

2. ENERGY IN AN ECOSYSTEM AUTOTROPHS
An organism that collects energy from sunlight or inorganic substances to produce food
Green plants and organisms that produce their own food in an ecosystem
Are primary producers

3. Can be herbivores, carnivores, omnivores, detritivores, or decomposers
HETEROTROPHS
Are consumers  Organisms that get their energy by consuming other organisms
Can be herbivores, carnivores, omnivores, detritivores, or decomposers
Herbivores: eat only plants
Carnivores: eat meat
Omnivores: eat plants and animals
Detritivores: eat dead matter
decomposers break down dead organisms through digestive enzymes

5. All heterotrophs perform some type of decomposition
consume other organisms and break down material into compounds
HOWEVER, it’s mostly the decomposers that break down organic matter and return nutrients to the ecosystem

6. MODELS OF ENERGY FLOW
Food chains and food webs used to model energy flow through an ecosystem
Grazing Food Web: begins with green plants like trees
From left to right: producers, primary consumers, secondary consumers
Detrital Food Web: begins with detritus
Bacteria and fungi are food for larger decomposers
Can be joined with grazing food web

7. In some forests organic matter lying on forest floor contains over 2x the amount of energy as in leaves!
Trophic Level: each step in the chain or web
Level 1 = autotrophs (primary producers)
Levels 2+ = heterotrophs (primary, secondary, and tertiary consumers)

8. FOOD CHAINS Shows one-way energy flow
Energy is gained by consuming lower levels
Organisms use energy for cellular processes (building cells and tissue)
Remaining energy released into surrounding
environment

9. Detrital Food Chain: dead organic matter  soil microbes  earthworms

10. FOOD WEBS
Represents the many interconnected food chains/pathways through a group of organisms

11. ECOLOGICAL PYRAMIDS
Shows the relative amounts of energy, biomass, or numbers of organisms at each trophic
level in
ecosystems

12. PYRAMID OF ENERGY
As you move up a level, you lose 90% of the energy that was previously there (only 10% goes to the next level)
Example:
Level 1 – 100% of energy
Level 2 – 10 % of energy remains (90% has been lost)
Level 3 – 1 % of energy remain (90% of Level 2s energy has been lost)

14. PYRAMID OF BIOMASS
Biomass: total mass of living matter at each trophic level (number of
animals multiplied
by their weight)
Decreases at
each trophic
level

15. PYRAMID OF NUMBERS
Each level represents the number of individual organisms
Decreases as you move up the pyramid