Ecosystem Ecology (PDF)

Ecosystem Ecology Why are big, fierce animals so rare?  Ecology in the news People suck. US uses 500,000,000 straws…per DAY Takes 200 years to break down…into tiny toxic particles Little is recycled, much ends up in ocean Need to know: Define an ecosystem, and understand how mate...

Ecosystem Ecology Why are big, fierce animals so rare?  Ecology in the news People suck. US uses 500,000,000 straws…per DAY Takes 200 years to break down…into tiny toxic particles Little is recycled, much ends up in ocean Need to know: Define an ecosystem, and understand how materials cycle and energy flows through ecological systems. Be able to differentiate between gross and net primary production, and understand the concept of production efficiency. Understand and be able to describe the concept of trophic (Lindeman’s) efficiency. Be able to describe the components of the nitrogen and water cycles. Be able to describe how nitrogen pollution affects ecosystems, and how industrial fertilizers have affected this process.  Ecosystems! What is an ecosystem?  Ecosystems! Ecosystem: a collection of organisms and the environment in which they live involves interactions between organisms and environment small as a pond or large as the Sahara desert Ecosystems include biota and physical environment Ecosystem ecology focuses on flux of energy and materials 3 important concepts here: Materials cycle… N …while energy flows through And decomposers are critical to closing the “loop” of materials And decomposers are critical to closing the “loop” of materials ”Brown Food Web” ”Green Food Web”  Decomposers/Detritivores Decomposers link primary producers and consumers Consist mainly of prokaryotes and fungi Convert organic matter to inorganic forms to be used by primary producers  Learning Catalytics: A tropical rainforest is an example of an ecosystem. Which of the following statements about matter and energy in a tropical rainforest is the most accurate? Please choose ONE answer that you think is best. A) Energy is recycled, but matter is not recycled. B) Matter is recycled, but energy is not recycled. C) Both matter and energy are constantly recycled. D) Neither matter nor energy are recycled.  Two important laws of thermodynamics 1st law: Energy is neither created nor destroyed (only transferred & transformed) Implication: Energy in = energy stored + energy reflected + energy dissipated as heat.  Two important laws of thermodynamics 2nd law (in a loose sense): during energy transformation, some energy becomes unusable Implication: energy transfer is not perfectly efficient* *because energy is lost as heat  Primary Production Photosynthesis: 6CO2 + 6H2O ----> C6H12O6 + 6O2 Gross primary production: the total amount of light energy converted to chemical energy by photosynthesis per unit time. GPP is a rate! (e.g. gC/m2/yr) Chemical energy is used by plants for growth, reproduction, respiration and maintenance Where is chemical energy stored? Glucose GPP = NPP + Rp Gross Net Respirationplant Primary Primary Production Production Rate at which new plant biomass accrues For many ecosystems, NPP is about 50% of GPP  Which ecosystem has higher NPP? Tropical forest Serengeti plains 1900 kcal/m2/yr 2000 kcal/m2/yr Important! NPP is new biomass produced per time, different from “standing crop” The Serengeti plains have insanely High NPP, but look like….  Learning Catalytics: Which experiment would work best to calculate the NPP of a grassland over the course of a month? A) Measuring the biomass of several areas of grass in a plot at the beginning and end of a one-month period. B) Putting a wire cage around several areas of grass, cutting the grass to the ground, and then measuring how much grass has grown in those cages at the end of a month.  NPP estimated from satellites Terrestrial systems contribute 52% of total NPP Aquatic systems contribute 48% of total NPP Why is oceanic NPP so low per unit area?  So what processes are involved in the transfer of energy from one trophic level to the next? Ectotherm 18% production efficiency Endotherm 1.6% production efficiency  Energy Flows and Energy Budgets Production efficiency = increase in biomass due to growth biomass consumed  Energy Flows and Energy Budgets Endotherms: production efficiencies about 1- 5% 85-95 % of total energy consumed used for maintenance Ectotherms: productions efficiencies of 10-50 % 65-80 % of total energy consumed used for maintenance LearningCatalytics Lizards and guinea pigs both eat the exact same type of kibble. If you’re farming for meat, and you want to maximize the production of your farm, which animal is a better choice? (note for the geeky among you: They are also the same size and same surface area : volume ratio) a. Lizards b. Guinea pigs  Energy Flows Across Trophic Levels Lindeman’s (trophic) efficiency: proportion of production transferred from one trophic level to the next. ~ 10 % Trophic Structure and Biomass Pyramids A terrestrial biomass pyramid  Not all biomass pyramids are right-side-up An inverted aquatic biomass pyramid Possible when rates of production of lower trophic levels are high Element Cycling: Overview Nutrient cycles referred to as biogeochemical cycles Highly mobile (gaseous) forms of carbon, oxygen, and nitrogen occur in the atmosphere and cycle globally Less mobile elements, including phosphorous, cycle on a more local level Nutrient cycling explained! The Four Main Element Cycles: C, H20, N and P The Nitrogen Cycle  Nitrogen Cycle Nitrogen is a component of proteins (e.g., protein required for photosynthesis), and is in nucleic acids Where is most of the nitrogen?  N N N N N  N2 + 3H2 -> 2NH3 High temp & pressure + metal catalyst What source of nitrogen is missing from this picture? Haber-Bosch Process  On to…the Water Cycle Water is essential to life. Water limitation slows productivity and decomposition  Bad things Currently, 1.2 billion lack clean water 18,000 people die EVERY DAY due to easily preventable waterborne disease  More bad things We are draining “fossil water” at a crazy rate  More bad things We are draining “fossil water” at a crazy rate Beijing is sinking 4” per year In central Mexico city, some areas sinking a foot a year Perspective The average American individual uses 100 to 176 gallons of water/day at home The average African family uses about 5 gal/ day (from ﾒWater Factsﾓ by Water Partners International, statistics taken from U.S. Geological Survey Fact Sheet "Water Q&A: Water Use at Home" and World Resources Institute, 1998-99 and 1996-97. "A Guide to the Global Environment."). Agriculture (according to Soil and Water specialists, Univ. of Calif. Agricultural Extension, working with livestock farm advisors Schulbach, Herb , et. al., Soil and Water, No. 38, Fall 1978, retrieved from Food Revolution. See you Friday!