Chapter 57 Why nutrient and energy are processed differently within ecosystems Energy flows through the ecosystem in the form of carbon carbon bonds When these bonds are broken the carbon is combined with oxygen making carbon dioxide which releases the energy used by organisms or the energy may be lost as heat energy does not recycle Nutrients include nitrogen Nutrients are passed from organism to organism as another consumes one organism All organisms die and become detritus food for the decomposers The last of the energy is extracted and lost as heat and the nutrients are returned to the soil and water to be taken up again Nutrients are recycled Energy not recycled Nutrients are b What are biogeochemical cycles They are how atoms of various chemical elements are said to move through ecosystems Biogeochemical cycles are the cycles of chemical elements involving not only biological organisms and processes by also geological abiotic systems and processes The include processes that occur on many spatial scales from cellular to planetary Also include processes that occur on multiple timescales from seconds biochemical reactions to millennia weathering of rocks They usually cross boundaries of ecosystems to some extent rather than being self contained within individual ecosystems They are chemicals moving through ecosystems through biotic and abiotic processes They usually cross boundaries of ecosystem one ecosystem might import or export chemicals to another c What are the most important conclusions derived from the study of the Hubbard Brook ecosystem Experiment in New Hampshire area was drained and whole area laid on granite rock all water leaves the system through evaporation or streams it is possible to measure inputs and outputs of nutrients Nitrate concentration in the runoff water from the deforested watershed is higher that the concentration in undisturbed watershed The undisturbed forests around Hubbard Brook are efficient at retaining nutrients Deforestation increased the loss of nutrients in runoff water from the ecosystem d Why is nitrogen fixation an important component of the nitrogen cycle Transformed to forms that planets cannot take there are primarily 2 forms NH4 Amonuim NO3 Nitrates those organisms that can fix nitrogen take atmospheric nitrogen into their bodies and convert it to nitrogen or ammonium Once they go into planets can flow into food web and the energy and matter are preserved in the ecosystem Most important way nitrogen go into plants Nitrogen fixation can happen in the soil also in freshwater ecosystems in streams e What organisms are responsible for fixing nitrogen from the atmosphere Microorganisms called diaztrophs fix nitrogen Cyanobacteria etc f What is the amount of chemically bound energy that is typically transferred from one trophic level to one above The size of each trophic level is determined by the productivity of the previous level Amount of chemical bond energy decreases as energy is passed from one trophic level to the next 50 of chemical bond energy is not assimilated and is egested in feces 33 of ingested energy is used for cellular respiration 17 ingested energy is converted into insect biomass Amount of chemical bond energy available to trophic level over time is about 10 of that available to the preceding level over the same period of time g What is the relationship between species and stability of an ecosystem Higher number of species the less sensitive the ecosystem is to the loss of one species Especially true for food webs when they are complex with multiple ways energy flows Consumers and producers and carnivores More complex the food web is the less it will be affected if a species disappears energy will still be flowing through a different path h How is species richness influenced by the characteristics of the ecosystem Primary productivity ecosystems with intermediate levels of productivity tend to have greatest number of species Habitat heterogeneity spatially heterogeneous abiotic enviroments are those consisting of many habitat types such as soil types they can be expected to accommodate more species of plants that spatially homogeneous environments accommodate more species Climatic factors more species might coexist in a seasonal environment than in a constant one on the other hand stable environments are able to support specialized species that would be unable to survive where conditions change Terminology Evaporation vaporization of a liquid that occurs only on the surface of a liquid conversion from liquid to a gas Transpiration process which moisture is carried through plants from roots and pores on leaves where it changes to vapor and is released to the atmosphere evaporation of water from plants Water cycle Liquid to gas liquid water from Earth s surface to oceans lakes and rivers occurs directly from surfaces this change requires thermal energy Nitrogen Cycle nitrogen is converted from a gas in the atmosphere to nitrogen containing substances in soil and living organisms then reconverted to a gas nitrogen absorbed by plants in the form of nitrates the plants are then eaten by animals and the nitrates are returned to the ecosystem when plant or animal dies Nitrification After NH3 has been synthesized other prokaryotic microbes oxidize part of it to form NO3 Denitrification Has to do with forms of nitrogen being put back into the atmosphere have to get energy that is present in molecules and put back into the atmosphere Takes atmospheric nitrogen and puts into nitrates Nitrogen fixation the synthesis of nitrogen containing compounds from N2 Producers autotrophic organism that serves as a source of food for other organisms in a food chain its an organism that can make its own food Autothrophs self feeders synthesize the organic compounds of their bodies from inorganic precursors Consumers heterotrophs Heterothrophs cannot synthesize organic compounds from inorganic precursors animals that eat plants and other animals they obtain energy they need to live by breaking organics compounds they have available Herbivores first consumer level Detritivores eat decaying matter Secondary productivity productivity of a heterotroph tropic level the rate that new organic matter is made by means of individual growth and reproduction in all herbivores in an ecosystem each heterotroph trophic level has one NPP Net primary productivity the GPP less the respiration of the primary producers represents the organic material made