BIO 311D 2nd Edition Lecture 39 Outline of Last Lecture I. Community Dynamics, Ecological SuccessionII. Trophic Interactions and energy flowOutline of Current Lecture I. Energy flow and trophic structure (How does this affect human k?)II. Nutrient cycling and eutrophicationCurrent LectureI. Energy flow and trophic structure A. Index Questionsa. Photosynthesis is a synthesis reaction not a respiration reaction. b. Both animals and plants respire and release CO21. Plants release CO2, but they use it for photosynthesis c. In cell respiration, animals and plants release CO2, and in photosynthesis plants release O2d. Carbon fixation: building organic compoundse. Heat is lost from biological system in the form of heatB. Where is photosynthesis occurring? C. Where is cellular respiration occurring? D. At each step of the food chain, there is a loss of usable energy for biomass production; based on 10% efficiency a. Which of these helps explain why there is less total biomass in predators at the top of a food chain than in organisms at lower levels?Useful energy is lost to cell work and heat at every transfer between levels of the food chain E. Where do humans fit in? How related to our K?a. Humans can act both as secondary and primary consumers b. What is “K” for humans on earth? c. Factors1. Abundance of water2. Distribution of food/ Change our food source 3. Disease – density dependent mortality 4. Natural disasters – density independent d. What is your ecological footprint?1. Available capacity vs. ecological footprint (ha per person)2. Using ecological footprint to determine the K the earth can hold II. Nutrient cycling and eutrophication A. Carbon cyclea. Producers use CO2 during photosynthesis, producing organic compoundsb. All organisms release CO2 in cellular respirationc. Follow a C atom d. Greenhouse gases: CO2 and methane Global warming (trapping heat) 1. Reduction in growth of the ozone hole through restriction of fluorinated hydrocarbons: (hole in the ozone has been getting smaller in the past 10 years) B. Biological Magnification a. Toxins in the environment (pesticides, heavy metals like mercury, plastic residues) become more concentrated in successive trophic levels b. Affects reproduction successc. Banning DDT (success story) – no longer threatened by egg-shell thinning: eagles, peregrine falcon, brown pelican, California condor d. Affecting humans: toxic aluminum levels, unsafe mercury levels in fish.1. Alters nervous system, etc. C. Nitrogen cyclea. Abiotic Biotic b. N2 > NH3 c. Atmospheric nitrogen Ammonia [nitrogen fixing bacteria, we and plants can’t do it] d. Humans need amino acids, that we have to get from our food e. How does nitrogen move between biotic and abiotic reservoirs?1. Decomposers: important for releasing into abiotic molecule2. Humans: release through uric acid, urea into the abiotic reservoir f. Cyanobacteria: nitrogen fixer, prokaryotes, carry on photosynthesis, trap energy to make
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