BIO 373 1st Edition Lecture 24 Outline of Last Lecture I Energy in Ecosystems a Primary production i Gross primary production ii Net primary production 1 Variations in NPP b Secondary production c Energy flow i Trophic levels 1 detritus Outline of Current Lecture I Energy in Ecosystems contd a Efficiency i Trophic efficiency ii Assimilation eggiciency iii Production efficiency iv Energy efficiency v Consumption efficiencies b Trophic cascades These notes represent a detailed interpretation of the professor s lecture GradeBuddy is best used as a supplement to your own notes not as a substitute c Biogeochemistry i Nutrients 1 Lithosphere 2 Atmosphere 3 Biosphere ii Nutrient storage Current Lecture Energy in Ecosystems Efficiency o Trophic efficiency Proportion of available biomass that is consumes o Assimilation efficiency Proportion of ingested biomass that consumer can assimilate with digestion What can the consumer use and what can t it use What can be assimilated goes towards production efficiency o Production efficiency Proportion of assimilated biomass used to produce new consumer biomass maintain tissues o NPP energy can be consumed and not consumed Not consumed becomes detritus Consumed energy can be assimilated or not assimilated Not assimilated becomes feces which becomes detritus Assimilated energy can go towards biomass or not o Energy not going towards biomass is used for respiration o Energy towards biomass goes to the growth biomass and maintenance of secondary producers o Energy efficiency The percentage of energy transferred from one trophic level to the next 10 energy to next trophic level 50 metabolism 40 detritus o Consumption efficiencies Tend to be higher for carnivores than herbivores Consumption efficiency is higher in aquatic ecosystems than terrestrial o Production efficiency is strongly related to thermal physiology and size of consumer Size affects energy usage Smaller organisms have greater surface area to volume ration so they lose a lot of energy to the envornment Top down like trophic cascades Rates of consumption at high trophic levels determines species competition Bottom up high availability of NPP Greater availability of limiting resources increases NPP o Trophic cascades Series of trophic interactions that result in changes in biomass and species competition at lower trophic levels Cascades can change Ex escessive fishing decreased food for sea lions decrease in sea lions decrease in food for whales whales begin to eat sea otters o a top down energy transfer higher trophic levels determine competition Biogeochemistry o Physical chemical and biological factors that influence movement and transformation of elements How nutrients are moving across atmosphere lithosphere and biosphere o Nutrients required for metabolism maintenance and growth Different organisms use different amounts of different inorganic and organic compounds depending on evolutionary history and cellular metabolic needs Lithosphere Rock sedimentation is the common way for organisms to obtain nutrients because rocks contain lots of minerals o They can sediment by icing over land slides physical fragmentation of any sort o Can also sediment by chemical weathering via rain water o Need to fragment so minerals have greater surface area o Important to soil formation Soil texture affects water availability for plants Smallest particles clay capture more water but don t release much to the plant and very good for holding nutrients Large particles sand can t hold much but releases a lot of what it does have to the plant Need intermediate mix of sand and clay particles for best water and nutrient capture and release Atmosphere Carbon in atmosphere from CO2 cellular respiration Nitrogen as N2 strong high energy bond N N o Symbiotic relationship microbes fix nitrogen to make a form that can be uptaken by plants and the energy needed for microbes to fix nitrogen comes from plants Delivers and transports nutrients with winds Biosphere Decomposition makes nutrients in detritus available and provides energy to decomposers o Breakdown into simpler molecules now more soluble in water in soil now available for plants Done by decomposers fungi microbes o Soil stores nutrients and is site of transformation o Climate controls activity of decomposers Low soil moisture limits decomposer activity via desiccation they need water Decomposition is most rapid at warm temperatures High moisture results in decreased oxygen concentration lowering the activity of decomposers need oxygen o Lignin Decreased rate of decomposition Low lignin to nitrogen ratio leads to increased decomposition rate Decomposition rates are higher in warmer soil if lignin to nitrogen ratio is similar Increased secondary compounds lead to decreased decomposition rates o Some nutrients released are used by the decomposers themselves High carbon to nitrogen ration will have low net release of nutrients because are limited by nitrogen availability Nutrient storage Plants uptake and store inorganic most or soluble organic forms of nitrogen as nutrients Plants recycle nutrients within their tissues