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Terms in this set (22)
Collection of species present in given space/time that are connected to each other through trophic interactions.
"Functioning" in a food web
The transfer of energy through the "structure" of the food web.
Transfer or energy from primary producers through a series of organisms. Heat is lost through each step, so number of trophic levels is limited. Food chains interact to give complex food webs
2 types of food webs:
grazing and detrital pathways
Range of resources an animal can use
Food web structure and functioning
Biodiversity, environmental stability, competition, strength of interactions
Wolf pack dispersed because...
No Muskox and hare left, so had to disperse for other food. This is how strength of interactions affects the food web structure and functioning
How to determine diets of top predators?
1 Prey remains 2 direct observation 3 Scat analysis (hard to find, biased towards larger prey, unknown individual, collected over vast temporal and spatial scales, and lots of samples) 4 Tissue analysis
Same no of protons, but different number of neutrons (atomic weight). Useful biological tracers, incorporated into biogeochemical processes at different rates than lighter isotopes.
Ratio of stable isotopes goes up as u climb the trophic levels
Direct observations, scat analysis, prey remains all are large prey biased, rare and only recent meals. Fatty acid signatures and stable isotopes are systematic, reflect diet ingested over time, and ingested biomass.
Flow of energy and matter through organisms and their environment
Physical Thermodynamic System
Energy of sunlight that drives circulation of wind and water, evaporation, etc.
Biological Thermodynamic System
Portion of sun's energy that enters photosynthesis and food webs.
Energy in, Maintenance, Storage, reproduction and growth out.
Exploitation Efficiency (EE)
Percentage of total production by one trophic level that is consumed by the next trophic level
Assimilation Efficiency (AE)
Percentage of food energy ingested that is assimilated across the gut wall and becomes available for metabolism.
Plants as Food
Large amounts of carbon burned off. Main waste C02 and fiber. Because of high carbon:nitrogen ratio, plants have high energy potential.
Plants as Food 2
However, because many heterotrophs can't digest lignin and cellulose, can't access energy. Hence most energy isn't available from plants, so AE is low.
Why is AE so low?
Many have no cellulolytic enzymes. Some herbivores utilize microfauna. 2 approaches: foregut fermenters, and hindgut fermenters.
Production Efficiency (PE)
Percentage of assimilated energy incorporated into new growth and reproduction (production). Remaining energy goes into respiration and lost as heat.
Ecological Efficiency (EcolE)
Percentage of production at lower trophic level that goes into production at the next trophic level.
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