Energy Flow in Ecosystems - Chapter 4, Lesson 2

Energy Flow in Ecosystems

• Energy flows in a one-way stream from primary producers to consumers in ecosystems.
• This flow is represented by food chains and food webs.

Food Chain and Food Web

• A food chain is a linear sequence of organisms that transfers energy from one to another.
• Food webs are complex networks of feeding interactions encompassing multiple food chains.

Primary Producers

• Phytoplankton are primary producers and consist of small floating, photosynthetic algae found near the ocean surface.
• They serve as a primary food source for small animal plankton.

Complexity of Feeding Relationships

• Many animals consume a variety of food sources, leading to more complex energy transfer dynamics than simple chains.

Role of Decomposers and Detritivores

• Decomposers break down dead organic matter, returning nutrients to the ecosystem.
• Detritivores, like shrimp and crayfish, consume detritus, playing an essential role in nutrient cycling.

Trophic Levels

• Trophic levels represent each step in food chains or webs, with primary producers at the first level.
• Energy transfer theoretically has no limit in the number of trophic levels, but only a small percentage (about 10%) of energy is passed on to the next level.

Ecological Pyramids

• Ecological pyramids model the relative amounts of energy or biomass at each trophic level.
• The shape of energy pyramids is influenced by energy transfer efficiency between levels.

Energy Transfer and Biomass

• Average energy transfer from one trophic level to the next is about 10%.
• Biomass indicates the total living tissue at each trophic level and is measured in grams of organic matter.
• The biomass available at a trophic level is partly determined by the energy present at that level.

Types of Pyramids

• A pyramid of biomass illustrates the amount of living organic matter at each trophic level.
• A pyramid of numbers shows the relative number of individual organisms at each trophic level.
• In some ecosystems, the pyramid of numbers may appear upside down due to a higher number of smaller consumers feeding on fewer larger producers, while the pyramid of biomass retains its shape.