Chapter1 The Nature of Science The environment impacts humans and humans impact the environment Applications of science broad interdisciplinary field Natural sciences include the examination of the natural world an example would be environmental science programs Social sciences include the examination of human interactions and institutions an example would be environmental studies programs Manipulative experiment Natural test Hypotheses are tested in different ways Manipulated experiments o Reveal causal relationships o Independent variable is manipulated o Yields the strongest evidence o Long term large scale processes cannot be manipulated Natural tests o Search for correlations among variables o Compare how dependent variables are expressed in different contexts o Have weaker evidence compared to manipulated experiments but show real world complexity o Results are not neat and clean or black and white o Addresses immense scale questions for example ecosystems Controlled experiment Sustainable system The effects of all variables are controlled except the independent variable whose effect is being tested We must limit our environmental impact while promoting economic development and social justice The single most important question we face is How can we develop sustainably Sustainable solutions must o Enhance quality of life o Protect and restore the environment that supports us Many solutions exist o Renewable energy sources o Improved agricultural practices o Habitat and species o protection o Reduced emissions of greenhouse gases Finding ways to live sustainably on Earth requires o A solid ethical grounding o Scientific understanding of our natural and social systems Tragedy of the commons Population and resource consumption grows Garrett Hardin s unregulated exploitation of public resources leads to depletion and damage o Grazing land forests air water Resource users are motivated by self interest o They increase use until the resource is gone Solutions o Private ownership o Voluntary organization to enforce responsible use o Governmental regulations Chapter2 Ecosystem modeling and geographic tools Model a simplified representation of a complicated natural process o Helps us understand processes and make predictions 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 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 Positive feedback loop Negative feedback loop output resulting from a system moving in one direction acts as an input that moves the 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 Melting ice exposes dark soil which absorbs sunlight Causes further warming and melting of more ice o Runaway cycles of positive feedback are rare in nature but are common in natural systems altered by humans Energy flow Sun energy flows in one direction through ecosystems energy is processed and transformed Energy is converted to biomass o Primary production conversion of solar energy to chemical energy in sugars by autotrophs during photosynthesis o Gross primary production total amount of chemical energy produced by autotrophs Most energy is used to power their own metabolism o Net primary production energy remaining after respiration Equals gross primary production cellular respiration It is used to generate biomass leaves stems roots Available for heterotrophs organisms that gain energy by feeding on others animals fungi microbes Two laws of thermodynamics First law of thermodynamics energy can change form but cannot be created or destroyed Second law of thermodynamics energy changes from a more ordered to a less ordered state o Entropy an increasing state of disorder Living organisms resist entropy by getting energy from food and photosynthesis Dead organisms get no energy and through decompositionlose their organized structure Macromolecule Macromolecules are building blocks of life o Polymers long chains of repeated organic compounds o Play key roles as building blocks of life Three essential types of polymers o Proteins o Nucleic acids o Carbohydrates Lipids are not polymers but are also essential o Fats oils phospholipids waxes steroids Macromolecules large sized molecules essential to life Net primary productivity Productivity rate at which autotrophs convert energy to biomass High net primary productivity ecosystems whose plants rapidly convert solar energy to biomass aglal beds and reefs tropical rainforests swamps and marshes are at the top of the list Nutrient cycle nitrogen Nitrogen makes up 78 of the atmosphere it is contained in proteins DNA and RNA o Essential for plant growth Nitrogen cycle describes the routes of nitrogen through the environment o Nitrogen gas is inert and cannot be used by organisms o It needs lightning bacteria or human intervention to become biologically active and available to organisms o Then it is a potent fertilizer Nitrogen must become biologically available Nitrogen fixation nitrogen fixing soil bacteria or lightning fixes nitrogen gas into ammonium o Nitrogen fixing bacteria live in legumes e g soybeans Nitrification bacteria then convert ammonium ions first into nitrite ions then into nitrate ions o Plants can take up these ions Nitrite and nitrate also come from the air or fertilizers Denitrifying bacteria convert nitrates in soil or water to gaseous nitrogen releasing it back into the atmosphere Animals obtain nitrogen by eating plants or other animals Understand basic terms e g respiration nitrification industrial fixation and photosynthesis Nitrification bacteria then convert ammonium ions first into nitrite ions then into nitrate ions Plants can take up these ions Industrial fixation fixes nitrogen on a massive scale overwhelming nature s denitrification abilities o Excess nitrogen leads to hypoxia in coastal areas o Nitrogen based fertilizers strip the soil of other nutrients Reducing soil fertility o Burning forests and fossil fuels leads to acid