Chapter 1 The Nature of Science Science a systematic process for learning about the world and testing our understanding of it o Learn by questioning observation testing discovery Knowledge gained from science can solve society s needs o Develop technology o Inform policy and management decisions Manipulative experiment Natural test Manipulative experiments reveal causal relationships o The independent variable is manipulated o Yields the strongest evidence o Long term large scale processes can t be manipulated Natural tests search for correlations among variables o Compare how dependent variables are expressed in different contexts o Weaker evidence but shows real world complexity o Results are not neat and clean or black and white o Addresses immense scale questions i e ecosystems Controlled experiment Sustainable system o The effects of all variables are controlled except the independent variable whose effect is being tested o Use natural resources wisely o Sustainability living within our planet s means o Earth can sustain humans AND all life for the future o We cannot sustain human civilization without sustaining Earth s natural systems o Earth s resources are like a bank account o If we deplete resources we draw down the account o Natural capital the accumulated wealth of Earth s resources We are withdrawing our planet s natural capital 50 faster than it is being produced o We must live off nature s interest its replenishable resources to be o Drawing down resources faster than they are replaced eats into sustainable nature s capital We cannot do this for long o Sustainable solutions must o Enhance quality of life o Protect and restore the environment that supports us o Many solutions exist o Renewable energy sources o Improved agricultural practices o Habitat and species protection o Reduced emissionsof greenhouse gases o Satisfies the triple bottom line Tragedy of common o Garrett Hardin s unregulated exploitation of public resources leads to depletion and damage o Grazing land forests air water o Resource users are motivated by self interest o They increase use until the resource is gone o Solutions o Private ownership o Voluntary organization to enforce responsible use o Governmental regulations Chapter 2 Ecosystem modeling and geographic tools o Model a simplified representation of a complicated natural process o Helps us understand processes and make predictions o Ecological modeling constructs and tests models to explain and predict how ecological systems work o Grounded in actual data and based on hypotheses o Extremely useful in large intricate systems that are hard to isolate and study o Example studying the flow of nutrients into the Chesapeake Bay and oyster responses to changing water conditions Positive and negative feedback loops o Feedback loop a circular process in which a system s output serves as input to that same system o Negative feedback loop output resulting from a system moving in one direction acts as an input that moves the system in the other direction o Input and output neutralize one another o Stabilizes the system o Example if we get hot we sweat and cool down o Most systems in nature involve negative feedback loops o Positive feedback loop instead of stabilizing a system it drives it further toward an extreme o Example white glaciers reflect sunlight and keep surfaces cool o Melting ice exposes dark soil which absorbs sunlight o Causes further warming and melting of more ice o Runaway cycles of positive feedback are rare in nature o But are common in natural systems altered by humans Energy Flow o Life interacts with its abiotic environment in ecosystems through which energy flows and materials are recycled o Understanding energy energy flow and chemistry increases our understanding of organisms o How environmental systems function o Energy and matter flow through ecosystems o Sun energy flows in one direction through ecosystems o Energy is processed and transformed o Matter is recycled within ecosystems o Outputs heat water flow and waste Two laws of thermodynamics o First law of thermodynamics energy can change form but cannot be created or o Second law of thermodynamics energy changes from a more ordered to a less destroyed ordered state o Entropy an increasing state of disorder o Living organisms resist entropy by getting energy from food and photosynthesis o Dead organisms get no energy and through decomposition lose their organized structure Macromolecule o Macromolecules are building blocks of life o Polymers long chains of repeated organic compounds o Play key roles as building blocks of life o Three essential types of polymers o Proteins o Nucleic acids o Carbohydrates o Lipids are not polymers but are also essential o Fats oils phospholipids waxes steroids o Macromolecules large sized molecules essential to life Net primary productivity o Productivity rate at which autotrophs convert energy to biomass o Net primary production energy remaining after respiration o High net primary productivity ecosystems whose plants rapidly convert solar o NPP increases with temperature and precipitation on land and with light and energy to biomass nutrients in aquatic ecosystems Nutrient cycle nitrogen o Humans greatly affect the nitrogen cycle o Nutrient biochemical cycle the movement of nutrients through ecosystems o Historically nitrogen fixation was a bottleneck limited the flux of nitrogen from air into water soluble forms o Industrial fixation fixes nitrogen on a massive scale o Overwhelming nature s de nitrification abilities o Excess nitrogen leads to hypoxia in coastal areas o Nitrogen based fertilizers strip the soil of other nutrients o Reducing soil fertility o Burning forests and fossil fuels leads to acid precipitation adds greenhouse gases and creates photochemical smog Understand basic terms e g respiration nitrification industrial fixation and photosynthesis o Respiration returns carbon to the air and water o Nitrification the conversion by bacteria of ammonium ions first into nitrite ions o Industrial Fixation nitrogen fixation performed by people to produce fertilizers and then into nitrate ions and industrial chemicals o Photosynthesis the process of turning the sun s light energy into high quality chemical energy produces food for plants o Watershed the entire area of land from which water drains into a given river o Hypoxia the condition of extremely low dissolved oxygen concentrations in a o System a network of relationships