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Ecology
Food Webs
17
Biology
Undergraduate 3
06/06/2010

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Term
FOOD WEBS
Definition
the trophic connections between organisms in a community
Term
FOOD CHAIN
Definition
a linear subset of a food-web showing links between species at different trophic levels.
Term
Within a food web there are several different trophic levels:
1rst level
Definition
Producers (autotrophs, photo or chemo-synthesizers)
Green plants,
algae in aquatic systems
Term
Within a food web there are several different trophic levels:
2nd level
Definition
Primary consumers (heterotrophs) Herbivores
Term
Within a food web there are several different trophic levels:
3rd Level
Definition
Secondary consumers
Primary carnivores
Term
Within a food web there are several different trophic levels:
4rth level
Definition
Tertiary consumers
Secondary carnivores
Term
Food Web examples
Definition
• Aquatic
• Terrestrial
• Grass land
• Tropical Forrest
Term
Types of food webs
-Qualitative(connectedness or topological food webs)
Definition
Who eats who, Connected or topoligical
Term
Types of food webs
-Quantitative
Definition
The strength of the reactions, energy flow, functioning web
Term
Properties of Food webs
S:
C:
I:
Definition
S: Number of Species = Web size
C: Connections= The ratio of the actual interactions to possible interactions (C=t*L/(S*(S-1)/2))
I: Interaction Strength
Term
Degree of omnivory:
Definition
Cannibalism, Intraguild predation
Term
FOOD-WEB STABILITY
Definition
• Predators less dependent on population of a single prey.
• More Redundancy – if one species removed, other species with similar functions can move in.
Term
MacArthur (1955) argued the more complexity
Definition
= more stability
Term
In 1973 Robert May: more complexity
Definition
less stability
Term
Weakly interacting species
Definition
stabilize community dynamics by dampening strong, potentially destabilizing consumer–resource interactions
Weak interactions are the glue that binds communities together and keeps them from falling apart!
Term
Average interaction strengths
Definition
decrease in diverse systems making them more stable
thus, decreasing biodiversity will increase average interactions strength and decrease stability
Term
Keystone Species
Definition
Species that have a greater impact than predicted by their biomass
All species are not equal in their influence on communities
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