Tag Archives: food chains

Food webs and energy transfer


Image source

Food chains illustrate the relationship between producers and consumers, showing the different trophic levels in an ecosystem. Because living organisms usually have more than one source of food, these food chains are often linked together, forming food webs. Food webs assist us to identify herbivores, carnivores, omnivores, scavengers, detritivores and decomposers in a community.

Not all relationships within an ecological community are predatory or feeding relationships. Some important relationships are parasitic, mutualistic (both organisms benefit), commensalism (one benefits, the other is not harmed) or parasitism (one benefits and the other is harmed, but usually not killed).

Populations, Communities and Ecosystems


Image courtesy of the Center for International Earth Science Information Network Last of the Wild Project. This image shows the human footprint of different biomes across the earth, measured on an arbitary scale of 0 (minimum) to 100 (maximum) of human impact on each terrestrial biome.  Although increased human population often leads to sharper species and ecosystem declines, the researchers found that land transformation probably poses the single greatest threat to biodiversity, resulting in habitat loss and/or fragmentation. The authors also found that increased human access through roads, rivers, and coastlines can lead to more pollution and invasive species. Both human access and land transformation have been fueled by increased access to fossil fuel and electrical power.

This week we start Unit 2: Area of Study B: Dynamic Ecosystems. You will need to understand the following terms:

  • biotic (living) and abiotic (non-living)  factors
  • population (group of organisms of the same species)
  • community (the different species that live in  the same area)
  • ecosystem (the physical environment and living organisms that live within it)
  • producers (autotrophs – usually use the sun’s energy and inorganic materials to produce energy)
  • consumers (heterotrophs – need an organis source of energy)
  • herbivores (eat producer organisms)
  • carnivores (eat consumers)
  • omnivores (eat producers and consumers)
  • detritovores (eat detritus – that falls to the bottom of an ecosystem)
  • food chain (single chain of feeding relationships)
  • food web (interlinking chains of feeding relationships)

Try these great interactive food webs from the Gould League.