8.2 beyond trophic levels Flashcards
what are stable isotopes?
different forms of the same element (different neutrons-different atomic mass)
-12C vs 13C
-14N vs 15N
what do isotopes have to do with living organisms?
-living organisms will reflect isotopic ratios based on how carbon was originally acquired in ecosystem (atmosphere, lake, etc) and then incorporated into tissues of organisms at higher trophic levels
-15N accumulates in organisms at a known rate and “moves up the food chain”. Ratios tells use alot about where a species sits in a food chain
what is the graph of nitrogen vs carbon (moving beyond trophic levels)?
in this hypothetical stable isotope graph and presumptive food web for a simple freshwater community, the dots represent measurements from individuals
-carbon isotopes are conserved when an organisms eats a food item, whereas nitrogen isotopes accumulate up a food chain
-the notation δ, denotes measurement from a tissue sample made relative to an isotopic standard
-the δ values are calculated as δ element=[(ratio of heavy to light isotopes in sample/ratio of heavy to light isotopes in the standard)-1]x1,000
what is moving beyond trophic levels in two different streams on the island of Kauai?
-the Limahuli is a relatively pristine stream dominated by native organisms, whereas the Opaeka’a is loaded with non-native species
-these figures indicate that the primary source of carbon changed with the introduction of invasive species (ie. more negative δ carbon values), and an entire trophic level was added to the top of the food web in the Opaeka’a
what are trophic subsidies?
-autochthonous: nutrient or carbon produced within an ecosystem
-allochthonous: nutrient or carbon input from outside the system
-there is a continuum of relative importance of allo- and autochthonous sources in the energy and nutrient balance
what is the Baja Island food web (trophic subsidies)?
what did they find out when they examined the ratio of allochthonous marine inputs to local terrestrial inputs on 19 Baja Islands?
found that marine inputs exceeded terrestrial inputs on 16 of the 19 islands
-note that smaller islands receive a larger portion of their inputs from external marine sources
what is an example of trophic subsidies?
what is the graph of relative total organic carbon and size of water?
what is the relationship between horses and seals?
what happened in Newfoundland?
-1992, the Newfoundland Cod fishery collapsed
what are the indirect effects that add complexity?
-strongly interacting species
-other important forms of indirect effects
what is a keystone an example of?
strongly interacting species
-the keystone in a stone arch is the critical center stone at the crown of the arch that balances the pressure from the two sides and holds the structure upright
what are examples of strongly interacting species?
A. sea otters are a keystone species in nearshore marine environments of the eastern pacific ocean. without seaotters, sea urchin abundances can grow to such high densities that they decimate the kelp forests that support much of the nearshore coastal environment
B. tiger sharks are thought to be keystone predators in the marine food web of Shark Bay
C. mountain lions are though to be potential keystone species in the greater ecosystem around yosemite national park
what are the four types of indirect effect interactions?
conceptual models of four common types of indirect effect interactions have solid arrows for direct effects and dashed arrows for indirect effects
-red arrows and minus signs indicate negative effect; blue arrows and plus signs indicate positive effects
what is the wolf example of other important forms of indirect effects?
what is another other important form of indirect effects?
african bush elephants are ecosystem engineers of the african savannas
