Topic 26: Trophic ecology Flashcards
Explain the concept of trophic levels, food chain and food web
- Trophic levels: the position of an organism in a food web
- describe how energy flows within ecosystems
- Food chain: energy flow between organisms among trophic levels
- Food web: real life is much of the time much more complex than food chain
Why are food chains short? (identify and describe the supported theories)
- The energy hypothesis:
+ only 10% of the energy produced in 1 trophic level is consumed by the higher one -> very low productivity
+ if an ecosystem is higher in productivity, it will have longer food chains. - The dynamic stability theorem:
+ small disturbance to low trophic level can magnify and greatly affect top predators
+ stable environments have longer food chains
How is trophic cascade different from food web and/or food chain?
- In food web or food chain: arrows point in the direction of energy being consumed
- Trophic cascade: downward arrows indicating the influence that top predators exert on lower trophic levels like primary consumers and producers
Identify and describe ecological interactions
- Mutualism: both organisms gain benefits
- Obligate organisms - symbiosis: ONLY survive if have each other
- Facultative organisms: able to survive without the other, BUT better from the interaction
- Competition: both organisms are affected
- Can be for food or mates
- Competition take up energy → higher energy expenditure
- Commensalism: (+/0)
- Amensalism: (-/0)
- Predation: herbivory, carnivory and parasitism
Link ecological interactions to the flow of energy through trophic levels using herbivory as an example
Herbivory - biggest interaction on the planet: yet plants are still everywhere ←Top predators exert control on number of herbivores
What factor determines the amount of energy passing through an ecosystem?
The net primary productivity of the ecosystem or in other words, how much energy/food available at the lowest trophic level at any time
Differentiate between interference/contest competition and exploitation competition
- Interference/contest competition: individuals harm each other for resources (e.g. fight to get mates)
- Exploitation: utilize 1 common limited resource
