BIOL 228 FINAL Flashcards
Define commensalism
Type of symbiosis where one species benefits and one is not really affected in a meaningful way –> epiphytes growing on trees
What are the two different kinds of mutualism?
Obligate and Facultative
First must be in the mutualistic interaction, other one doesn’t have to be
Define ecosystem ecology
Ecosystem ecology examines the flow of energy and chemical cycling in habitats, as well as, the effects of natural and human-induced disturbances on ecosystems (ex; air/water pollution, tree harvesting)
Ecosystem science tends to focus more on processes than on individual organisms.
Explain the different pathways of energy and chemicals in a system
Energy flows through the components of an ecosystem
Chemicals and nutrients are recycled in a circular manner throughout an ecosystem
What are the four most important kinds of energy in an ecosystem?
Thermal energy –> heat
Radiant energy –> light –> drives many processes (from the sun), such as water cycle and air currents, a small amount is used for photosynthesis
Kinetic –> motion
Chemical
What is PAR?
Photosynthetically Active Radiation
The fraction of radiant energy that is available for use by photosynthetic organisms
Use CO2 and H2O plus radiant energy to make sugar and O2
Define primary production
The rate at which photosynthetic organisms convert solar energy into chemical energy (organic compounds)
Measured over a unit of time
Explain the difference between GPP and NPP
Gross Primary Production (GPP) → total amount of carbon fixed per area per unit time
Net Primary Production (NPP) → Total amount of carbon fixed per area per unit time minus cellular respiration ( R ) by the autotrophs
–>Represents the carbon available for the rest of the food chain
Explain the difference between GPP and NPP
Gross Primary Production (GPP) → total amount of carbon fixed per area per unit time
Net Primary Production (NPP) → Total amount of carbon fixed per area per unit time minus cellular respiration ( R ) by the autotrophs
–>Represents the carbon available for the rest of the food chain
Explain the light and dark bottle method for measuring both GPP and NPP in an ecosystem
Respiration will occur in both bottles, whereas photosynthesis will only occur in the clear bottle
NPP will occur in the light bottles
GPP will be the NPP from the light bottles plus the bottle of just respiration (dark)
NPP = O2 in clear bottles after 12 hours - initial O2 concentration
R = (O2 will go down) Initial O2 content - final O2 concentration in dark bottles
GPP = NPP + R
What main factors control or limit primary production in a terrestrial or aquatic ecosystem? (4/3)
Terrestrial
Intensity and duration of sunlight –> more intensity means more available energy, longer duration increases growing season
Temperature –> photosynthesis is better at warmer temps
Moisture and precipitation –> usually better when higher, however too much causes water logging meaning roots cannot properly uptake nutrients
Nutrient levels, N
Aquatic
Intensity and duration of sunlight
Temperature
Nutrient levels, N, P, Fe
Explain the relationship between precipitation and temp on an ecosystems productivity in terms of plants
Plants exchange gasses in stomata
Water is lost through stomata
When hot and dry plants close stomata to prevent water loss –> loss of water is called transpiration
Low CO2 in leaf, high O2
Closing means gasses cannot be exchanged
Reduces primary production in C3 plants
Goes into alternate version of Calvin cycle called photorespiration where plants are not growing
Define evapotranspiration and describe its relationship with primary production
Evapotranspiration is the loss of water vapor to the atmosphere from plants AND soil
In warm, wet environments, evapotranspiration is high
High evapotranspiration = high primary production
Explain how nutrient limitation may exist even if there is a lot of that nutrient
Nutrients can occur at a high rate but not be bioavailable
Therefore the limiting step becomes the rate at which a nutrient can become mineralized (become bioavailable)
Faster it can mineralize = higher PP
What are the four nutrients that limit PP in aquatic ecosystems?
NH4 (ammonium and nitrates) –> important for proteins synthesis in phytoplankton
PO4 –> used in ATP transfer, and cell membranes in algae –> P is most limiting nutrient in lakes
Fe –> mainly oceans, fixes N
Si –> used in diatom skeletons
Explain what is meant by “Ironing the Oceans”?
John Martin found that Fe was the limiting nutrient in pacific ocean
Open ocean fertilization experiments have been conducted trying to provide ocean with more Fe, increasing PP and lowering global temp
Ironing the Ocean
Random dude Russ George straight up dumped a buncha iron in the ocean to try and stimulate plankton growth to provide more food for salmon
There was not monitoring behind this, science isn’t there yet
Ended up producing a bunch of methane gas, that some phytoplankton produce toxic chemicals when too stimulated
Explain the effect of grazing on PP
Low grazing → rates permit nutrients to be locked up in biomass in vegetation, rendering the nutrient unavailable for further plant production
Moderate grazing → nutrients are rapidly released back into the environment for reuptake into vegetation, stimulating further plant production
–>peak primary production
Overgrazing → reduces vegetation biomass to such low levels that autotrophs cannot increase biomass in the ecosystem (low production)
Explain the relationship between habitat complexity and NPP, also explain the term rugosity
NPP is higher in more complex ecosystems
Rugosity –> refers to the degrees of wrinkling of a surface
Forests with tree biodiversity have gaps in the canopy (high rugosity) allowing greater light use effiency
Define the terms trophic structure and food chain, what are the different trophic levels in a food chain?
Trophic structure–> determines the route that energy flows through the ecosystem
Food chain–> the sequence of food transfers from trophic level to trophic level
Producers (autotrophs)–> organisms that make organic food molecules from CO2, H2O and other inorganic raw materials, e.g., a plant, an alga, or a photosynthetic bacterium
Primary consumers (herbivores)–> organisms that eat only producers (e.g., a grasshopper, aphid, or bison)
Secondary consumers –> organisms that eat primary consumers (e.g., small mammals, frogs, spiders)
Tertiary consumers –> organisms that eat secondary consumers (e.g., a snake, a pike)
Quaternary consumers–> organisms that eat tertiary consumers (e.g., hawks, killer whales, muskies)
Detritivore/decomposer –> a consumer that eats detritus, the dead material produced by all trophic levels (e.g., plant waste and carrion). Such organisms include earthworms, and vultures, but the most important decomposers are bacteria and fungi
Some animals may operate at multiple trophic levels at once or throughout their lives (omnivores, amphibians)
Food chains start with many microscopic organisms
Define secondary production
The rate of biomass production by heterotrophic or consumer organisms
Expressed in g C/M2/day, or kJ
Explain the three process that detail energy transfer efficiencies within a trophic level
Ingestion efficiency (IE) –> % of total productivity available at one trophic level that is consumed by the trophic level above
–> generally more plant biomass is available than can be eaten (bison don’t eat ALL the grass), the rest of the plant biomass dies without being eaten
–> 25% in grasslands
–> for secondary consumers is % of herbivore productivity consumed by carnivore (5-100%)
–> prey adaptions like spines or shells lower IE
Assimilation efficiency (AE) –> fraction of ingested energy that is assimilated (crosses gut lining)
–> energy that is not assimilated is egested as feces
–> consumption of plants is about 30%, cellulose and lignin are hard to fully digest
–> carnivores usually have AE of 80%, some shells like chitin cannot be digested either
–> food quality refers to the ease at which food is assimilated
–> Improvements in mastication, digestive enzymes, symbiotic relationships and the length and shape of the gut represent features that can be modified through evolution to improve AE
Production efficiency (PE) –> proportion of the assimilated energy that is converted into new biomass, remainder lost to respiration
–> resulting biomass = secondary production
–> invertebrates (ectotherms) have much higher PE than vertebrates (endotherms) as endotherms use most of their assimilated energy in respiration to maintain constant body temp
What is trophic transfer efficiency and what does it imply (3)?
The amount of energy available to an upper trophic level –> IE x AE x PE = TTE
Usually around 10%, meaning less and less energy is available to upper trophic levels, resulting in the food chain being finite, hard to pass 5 levels
10% (0.1) x 5 levels results in 0.01% of initial energy remaining
Implications
Top consumers much be mobile to search a wide area
Must have low density, not enough energy to maintain dense predator populations
Top consumers more susceptible to extinction
Explain the relationship between grazing and detrital food chains in terms of production
Grazing food chains rarely dominate the energy flow (2% in a forest example)
Detrital food chains are responsible for most of the secondary production (35% GPP in same forest)
Two are closely integrated, energy for detrital comes from all steps of grazing
energy flow is unidrictional in grazer, multidirectional in detrital
plankton communities will have a much higher proportion going to grazing food chain as no cellulose
What are the three kinds of ecological pyramids?
Biomass, Abundance and Energy
Can be inverted, usually the fault of trees (lots of mass, little density)
Energy cannot be inverted ( tropohic transfer efficiency)
What is the impact of the human energy pyramid
They can choose their own, due to TTE, technically 10x more humans could be fed if we only ate plants and not meat
75% of agricultural land is for feeding animals not humans
70% of water withdrawals are for agriculture
Explain the issue with DDT contaminant cycling
Certain top predators have high concentrations of toxins DDT despite low concentraions in the environment
DDT is resistant to breakdown and accumulates through Biological magnification
DDT is transferred with a greater efficiency than the general trophic efficiency
DDT interferes with egg shell formations and can be toxic with age
Other persistent organic pollutants (POPs) accumulate in cold regions where they condense
Explain the issues with Hg levels in tuna (article)
in 2007, Hg levels were above limit in canned tuna
More Hg accumulates in older fish/ higher up the food chain
Hg binds to proteins in tissue
Biomagnifys Hg
