Figure 24.6: Food web in the Arctic Ocean. ( 9 )is shown inFigure 6. Due to the energy loss in food chains, it takes many producers to
support just a few carnivores in a community. For example, there are far fewer hawks than
acorns in this food chain.
Each step of the food chain reflected in the ecological pyramid is called atrophic level.
Plants or other photosynthetic organisms are found on the first trophic level, at the base
of the pyramid. The next level would be the herbivores, then the carnivores that eat the
herbivores. The energy pyramid inFigure24.7shows only three levels of a food chain, from
plants (producers) to hawks (carnivores). Because of the high rate of energy loss in food
chains, there are usually only 4 or 5 levels in the chain or energy pyramid.
Lesson Summary
- Producers, which include photosynthetic organisms like plants and algae, can make
their own food from simple inorganic compounds. - Consumers must obtain their nutrients and energy by eating other organisms, while
decomposers break down animal remains and wastes to obtain energy. - Food chains and food webs are visual representations of feeding patterns in an ecosys-
tem. - As energy is transferred along a food chain, energy is lost as heat.
Review Questions
- How do decomposers obtain energy?
- What happens to 90% of the energy that passes from one step in the food chain to the
next step? - For #’s 3 - 5, Analyze the following food chain: algae -> fish -> herons