BIO120H1 Lecture Notes - Lecture 10: Detritivore, Herbivore, Lignin
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Lecture 10: Trophic relationships in communities
Trophic eco = who eats what?
Flow of energy through food
Plants don’t eat anything, but sunlight
Organisms came up with defensive mechanisms to not be eaten – to boost up their fitness
Trophic levels – based on the function in the trophic flow in the whole community
- Primary Producers = plants
- Primary consumers = herbivores(insects)
- Secondary consumers = carnivores who eat herbivores
- Tertiary consumers = carnivores who eat secondary consumers
- Detritivores = eat dead organic matter
Food chain and food webs
- Trophic connections among species can be analyzed as interaction webs with network
properties like ‘connectance’. Getting idea from internet web.
- If we have a lot of organisms who eat each other we get a food web
- Trophic relations can determine community structure in ways that can be investigated by
Interaction strengths are assessed by removal experiments. Think of tomato experiment from the lab:
control group and insecticide treatment
Example from the lecture:
Goldenrod beetles suppressed
High plant diversity
Low plant diversity
Hairston, Smith & Slobodkin, 1960: trophic cascades (HSS)
Proposition: by just looking at the world we can understand how tropic levels are connected
- The world is green: plants are not being limited by herbivores, because of the indirect effect of
carnivores eat the herbivores, thus, not controlled by food supply, but by predation.
- Indirect effect: one trophic level exerts influence on a second by affecting a third
- Cascades involve effects that alternate across trophic levels
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