Ecology - Food Webs
Terms
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- Trophic Cascade
- When changes in one trophic level indirectly has much larger changes to all the trophic levels.
- Community
- a group of species that co-occur in time and space
- Energetic Hypothesis
- The length of a food chain is limited by the inefficiency of energy transfer along the chain. (10% rule) = a reason why food chains are short.
- Dynamic Stability Hypothesis
- Long food chains are less stable than short food chains, in recovering from environmental setbacks = a reason why food chains are short.
- Food Chain Theory
- The world is green because predators hold herbivores in check (Odd # of trophic levels). The world would be barren if the grazers highly suppressed plant growth (Even # of trophic levels)
- Faults of Food Chain Theory
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-The greens could be inedible.
-Consumers are co-limited by predators and food (or other factors)
-Omnivory blurs trophic levels
-Factors other than consumers or food limit populations - Keystone species
- A species not necessarily abundant, but without them the entire trophic system would undergo huge imbalance.
- Facilitation (founder species)
- These alter the structure or dynamics of the environment, having positive effects on the survival and reproduction of some of the other species in the community.
- Biomass
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The total mass of all individuals in a population:
-dominant species are the most abundant, with the most biomass - Reasons for species dominance
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1. The dominant species are most competitive in exploiting limited resources such as water or nutrients
2. They are the most successful at avoiding predation or the impact of disease.