Food webs
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Food webs

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Food webs Food webs Presentation Transcript

  • Food Webs Mapping out predator-prey relationships
  • Food chains represent flow of energy in a community but over-simplify the predator-prey relationships. Most organisms have multiple prey species and multiple predators (they eat many different things and get eaten by many different things).
  • A food web shows multiple food chains within a community. cc licensed flickr photo by cicadas: http://flickr.com/photos/cicada/2569385115/
  • Some (parts of) food webs consist of food chains that begin with plants. These are called grazing webs cc licensed flickr photo by cicadas: http://flickr.com/photos/cicada/2569385115/
  • Some (parts of) food webs consist of food chains that begin with plants. These are called grazing webs cc licensed flickr photo by cicadas: http://flickr.com/photos/cicada/2569385115/
  • Some (parts of) food webs consist of food chains that begin with dead organic matter. These are called detrital webs cc licensed flickr photo by cicadas: http://flickr.com/photos/cicada/2569385115/
  • Some (parts of) food webs consist of food chains that begin with dead organic matter. These are called detrital webs cc licensed flickr photo by cicadas: http://flickr.com/photos/cicada/2569385115/
  • There is often overlap between the grazing and detrital food webs. Which populations here are part of both webs? Which are only in the grazing web? Which are only in the detrital web? cc licensed flickr photo by cicadas: http://flickr.com/photos/cicada/2569385115/
  • Food Web stability In some food webs, the populations in the web can survive if one species is removed. Other populations can fill in as prey or predator species. A food web with more populations in it and/or more links between populations is less likely to collapse due to the removal of one species. (A community collapses when all/most of the populations in the community suffer sudden, dramatic population decrease.) In some communities, there are species that, if removed, can lead to collapse of the entire community. These are called cc licensed flickr photo by Martin LaBar (going on hiatus): keystone species. http://flickr.com/photos/martinlabar/3376987854/
  • Species at Risk in Canada (handout - write answers in your notes) How many species in Canada are currently classified as at risk Since the first European settlers arrived in North America: how many Canadian species are to known to have become extinct? how many species are no longer found in Canada? What are three reasons why many species in Canada are currently at risk? What is COSEWIC? What are they responsible for?
  • Species at Risk in Canada (handout) What do each of the following classifications for species at risk mean Extinct Extirpated Endangered Threatened Special Concern What has been done to help the recovery of the Peregrine Falcon anatum subspecies?
  • Species at Risk in Canada (handout) What has caused the North Atlantic Right Whale to be classified as at risk? What was the size of the entire population in 2004? What is being done to protect the Right Whale? What are two things that can be done to help species at risk? Why should we be concerned about species at risk?