Unit 4: Ecosystem Energies Flashcards
What is an ecosystem? What is ecosystem energetics? How is energy often measured?
Ecosystem: a community of organism interacting with their physical environment under the influence of environmental factors.
Ecosystem energetics: The study of how energy is fixed by autotrophs and made available to heterotrophs (how does energy flow through the food web and does it do it efficiently?)
Energy is often measured as biomass, which is the dry weight of organic matter in the ecosystem. this measures how much carbon they have taken in to build themselves, and by measuring how this changes through the food web, you can see how energy is transferred through the food web.
What are primary producers? What tropic level do they reside in? What type of production do they carry out? What is the rate at which energy is fixed in the first tropic level called?
Primary producers: organisms residing in the FIRST TROPIC LEVEL that fix inorganic nutrients into organic molecules, and so they are essentially producing the energy required for the entire ecosystem. these are autotrophs, and they do this by converting CO2, H2O and sunlight into energy that can be used in the ecosystem (C6H12O6 — high energy molecule that can be broken down and utilized by consumers).
This production is called primary production!
The rate at which energy is fixed in the first trophic level is called primary productivity!
What is the difference between production and productivity?
Production is what reaction is being done, and this is measured in mass of carbon produced. Productivity is the rate at which this production is done, and this is measured in tonnes carbon fixed / (km^2 x year).
What is gross primary production? What is net primary production? What is net PP measured as, and what does it tell us?
GPP: This is the total amount of energy fixed into organic molecules in an ecosystem (how much C6H12O6 and other molecules are produced by photosynthesis?).
NPP: this is the net amount of production that can actually be passed onto the next generation. Because a lot of this production is used for cellular respiration in the plants, and also in their activity such as defence, and hence this is not biomass that can be eaten by the next generation to be passed on. So this is the amount of energy used for growth, which can then be taken in by the next trophic level. This NPP is measured as biomass, as it is the molecules that others can take in and use for their growth.
NPP: GPP - (EnergyRMR + Energy activity)
So NPP = the amount of energy the producer makes, minus the amount it uses for itself, which is also the amount fo energy used for growth.
NPP tells us how much energy is available for other trophic levels, and hence indicates how efficient that energy transfer is throughout the food web.
Which ecosystems on earth have the highest NPP and why?
Rainforests and land in general will have the largest NPP, because they have a lot of primary producers per unit area and hence can produce the most energy which can be passed onto the next trophic level.
Where is the most productivity occurring in terrestrial ecosystems? What about aquatic ecosystems?
In terrestrial areas, the most productivity occurs in rainforests and boreal forests, and some occurs in grassland areas but less, because grass is so much smaller and so it can’t produce as much hydrocarbons and energy as tree can.
In aquatic ecosystems, the most productivity occurs in the shallow parts of the ocean where the most upwelling’s are, so more nutrients are swirling throughout the water and allowing for more producer growth. Erosion also brings more nutrients in. The shallower areas also have more algae and plants that are close to the sun, so they can do more photosynthesis and hence produce more energy. Deeper areas have less plants and also less nutrients, leading to less PP.
How does light intensity affect primary productivity?
As light intensity increases, PP slowly increases due to more photosynthesis being able to occur. But one it reaches a certain point, this is the maximum amount of light that can be efficiently taken in. Once it surpasses this point, the light is too strong and causes mutations to DNA and other parts of the plant, leading to damage and hence a drastic decrease in PP.
How does temperature affect primary productivity?
As temperature increases, molecular motion increases so particles have more energy to complete reactions of photosynthesis and hence more biomass and growth can be produced, allowing for increased primary productivity. However once temperature increases past a certain point, it begins to damage enzymes carrying out these reactions because those enzymes are too energetic and begin to denature. So after an optimum it will drop off.
But this is not a main factor in PP due to large variance in the plotted points.
how does precipitation effect PP?
As precipitation increases, NPP increases because there is more water available for photosynthesis. However once too much is produced there will be light limitations due to increased cloud coverage, and water logging and mold, and so NPP will decrease after an optimum.
How does nitrogen affect NPP?
N is soluble, so it easily washes away through erosion with rainfall, and therefore it tends to be more limiting on land. limiting factors, due to Leibegs law of the minimum, are what limit growth because no matter how much excess the other factors are in, growth cannot occur without enough of the one factor. So as limiting factors increases, NPP will increase proportionally.
But in places where other factors are limiting factors — such as water in desserts — nitrogen no longer is the limiting factor and so increasing it will not increase growth because there is not enough water present for this to occur.
How does phosphorus affect NPP?
Phosphorus is insoluble in water, so it tends to remain in terrestrial areas and hence is more limiting in water. So in aquatic ecosystems, increasing its concentration will have a pretty strong effect on growth. but again if other things become limiting, it will have a lesser effect.
What are primary consumers? What trophic level are they a part of? What is their other name and why? What percentage on average of the GPP from trophic level 1 do they get? What is their biomass production called?
Primary consumers are the organisms that consume the biomass of primary producers (plants) and hence they are called herbivores because they eat these plants. Since they only get 10% of GPP from trophic level 1, they will be much smaller in population then trophic level one.
They also use the energy taken in (NPP from TL1) for respiration, growth and locomotion (activity), and so their NSP (net secondary production) is the NPP - (energy activity + energy respiration) = biomass produced or energy used for growth, as this can be consumed by the next trophic level.
Their biomass production is called secondary production.
What trophic levels are secondary or tertiary consumers found in? What about quaternary consumers? What trophic levels are carnivores and omnivores found in?
Organisms that consume the organic molecules of primary consumers AND primary producers are omnivores, and these could be found in the 3rd or 4th trophic level (but technically are also part of the 2nd trophic level).
1st trophic level: Primary producers
2nd trophic level: Primary consumers
3rd trophic level: Secondary consumers
4th trophic level: Tertiary consumers
5th trophic level: Quaternary consumers
Since TL1 is PP and TL2 is PC, after that your consumer number is one less then your TL number.
What are decomposers and what type of production do they do? What trophic level are they a part of?
Decomposers consume dead organic matter of all levels, and recycle these nutrients to be up-taken by primary producers (Completing the cycle of nutrients).
They are always the last trophic level of the ecosystem, and because they eat biomass of other organisms, they are doing secondary production).
VERY IMPORTANT FOR NUTRIENT CYCLING!
What does a simple terrestrial food chain look like (with 5 trophic levels including the “last” one? What things cycle and what things flow?
Simple terrestrial food chain:
Solar energy —> Primary producers—> Primary consumers —> Secondary consumers —> Tertiary consumers —> Detritivores —> matter back to the primary producers
Energy flows through the system. It comes in from the sun, and majority of it is lost because reflected back into space. But some is taken in by PP, which use a lot for respiration adn export and activity, which just releases that energy to the surroundings, resulting in flow. Some also is not eaten by the next trophic level and hence is broken down by detritovers, leading to even more energy release to the environment and also consumed for their activity. so although some energy may be cycled back to the primary producers by the detritivores, most is lost to the surroundings resulting in this “flow”.
But the nutrients are always going to flow through an ecosystem, and will rarely leave that ecosystem. The detritivores are essential in recycling these nutrients back to the primary producers.
