1. Unit 4:
Energy Flow
Objective #1: Interrelationships and energy
flow within a food chain and food web

2. Levels of Organization
• The biosphere is where all life exists
• Ecosystems include living (biotic) and
non-living (abiotic) factors

3. Levels of Organization
• Populations consist of organisms of the
same species living in an area
• Communities have several populations in
an area

6. Energy Flow
• Living things need energy
• For growth, reproduction, metabolic
processes
• No energy  No life!
• Where does energy come from?

7. Energy Flow: Producers
• The SUN provides energy
• Producers make food
(autotrophic)
• Plants and some bacteria
are photosynthetic
• Some bacteria are
chemosynthetic

8. Energy Flow: Consumers
• Heterotrophs rely on other organisms for
their energy
• ie: herbivores, carnivores, omnivores,
scavengers, decomposers, and detritivores

9. Food Chains
• Energy is transferred through an
ecosystem when organisms eat or are eaten

10. Trophic Levels
• Feeding levels in a food chain or web
• 1st Trophic Level – Producers
• 2nd Trophic Level – 1st Order (Primary) Consumer…ETC
• Each consumer depends on the trophic level
below it for energy!

11. Figure 3-8 A Food Web
Food Web
Section 3-2
• Many food chains
together form a
food web

12. Pyramid of Energy
• 10% of the energy at one trophic level is
available to the organisms at the next level.

13. Biomass Pyramid
• The amount of living tissue and
thus potential food
• Typically the greatest biomass is
at the base

14. Pyramid of Numbers
• Relative number of individual
organisms at each level
• In certain ecosystems, it is NOT
pyramid shaped