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Biology 2483A Lecture Notes - Lecture 15: Trophic Cascade, Herbivore, Species Evenness

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indigolouse230
2 Dec 2014
School
Western University
Department
Biology
Course
Biology 2483A
Professor
Lisa Henry

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Document Summary

Communities are groups of interacting species that occur together at the same place and time. In practical terms, ecologists usually define communities based on physical or biological characteristics. Food webs organize species based on trophic or energetic interactions. Trophic levels: primary producers (autotrophs) plants and algae, primary consumers herbivores, secondary consumers carnivores, tertiary consumers carnivores. Food webs do not include nontrophic interactions (horizontal interactions, such as competition). Interaction webs more accurately describe both the trophic (vertical) and non-trophic (horizontal) interactions than a traditional food web. Community structure is the set of characteristics that shape communities: Species richness the number of species in a community. Species diversity combines species richness and species evenness. The most commonly used species diversity index is the shannon index: 1 p i ln p i pi = proportion of individuals in the ith species s = number of species in the community. Two communities could have identical species diversity values, but have completely different species.

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Related Questions

Food web studies have come a long way since the early 1900s when ecologists began developing these tools to understand species interactions and ecosystem level processes (2-5). From that point forward, food web ecology grew rapidly developing into its own sophisticated, technical sub-discipline of ecology (2-5). Tools involved in tracking species interactions, as well as the quantitative tools to analyze food webs, improved and diversified (6-11). These technological innovations were accompanied by the construction of several high quality food webs from diverse biomes (7). The wide diversity of food webs provided the opportunity to explore some of the fundamental properties pertaining to the structure and function of ecosystems (7). However, there is still much about food webs that remains unexplored, particularly investigations of understudied taxonomic groups like the parasites that are typically not included or aggregated in food webs (12-17). Here you have the opportunity to investigate a food web of your choice and explore some of the implications related to food web construction and analysis.

Conduct a literature search and find a peer-reviewed scientific article describing an original, empirical food web and answer the following questions.

Questions

What biome and scale does the food web represent? For example, was it a lake, a pond, a desert? How was the extent of the food web determined? Was it based on the physical characteristics, biological community or arbitrarily by the researchers based on their specific question?

What taxonomic groups were included in the food web? What level of taxonomic identification (species, family, order, etc.) was used for those groups? Was it the same for all or did it vary?

What groups were excluded or aggregated in the food web? What are some of the characteristics of these groups? How might the characteristics of these organisms contribute to this issue?

How did the researchers determine the types of interactions taking place in their food web? What general approaches were used and how did this differ among taxonomic groups?

Overall, how might excluding or aggregating different groups have influenced the results of the study? How might the researchers address these issues?

Food web studies have come a long way since the early 1900s when ecologists began developing these tools to understand species interactions and ecosystem level processes (2-5). From that point forward, food web ecology grew rapidly developing into its own sophisticated, technical sub-discipline of ecology (2-5). Tools involved in tracking species interactions, as well as the quantitative tools to analyze food webs, improved and diversified (6-11). These technological innovations were accompanied by the construction of several high quality food webs from diverse biomes (7). The wide diversity of food webs provided the opportunity to explore some of the fundamental properties pertaining to the structure and function of ecosystems (7). However, there is still much about food webs that remains unexplored, particularly investigations of understudied taxonomic groups like the parasites that are typically not included or aggregated in food webs (12-17). Here you have the opportunity to investigate a food web of your choice and explore some of the implications related to food web construction and analysis.

Conduct a literature search and find a peer-reviewed scientific article describing an original, empirical food web and answer the following questions.

Questions

1.What biome and scale does the food web represent? For example, was it a lake, a pond, a desert? How was the extent of the food web determined? Was it based on the physical characteristics, biological community or arbitrarily by the researchers based on their specific question?

2.What taxonomic groups were included in the food web? What level of taxonomic identification (species, family, order, etc.) was used for those groups? Was it the same for all or did it vary?

3.What groups were excluded or aggregated in the food web? What are some of the characteristics of these groups? How might the characteristics of these organisms contribute to this issue?

4.How did the researchers determine the types of interactions taking place in their food web? What general approaches were used and how did this differ among taxonomic groups?

5.Overall, how might excluding or aggregating different groups have influenced the results of the study? How might the researchers address these issues?