Chapter 2 Environment Systems, Matter & Energy LECTURE VIDEO

this week we’ll be taking a look at chapter 2 environmental systems which includes matter energy and ecosystems during this chapter we’ll take a look at environmental systems the fundamentals of matter and chemistry energy and energy flow photosynthesis and cellular respiration ecosystems and their interactions the fundamentals of landscape ecology we’ll revisit the term ecosystem services from Chapter one and we’ll look at some various chemical cycles which are called biogeochemical cycles our central case study in this chapter involves the vanishing oysters of the Chesapeake Bay it’s an interesting story of how the Chesapeake Bay was once the largest oyster fishery in the world but unfortunately due to over harvesting pollution and habitat destruction over the years it was ruined and it’s not just the ecosystem that’s at stake there it’s also the economy of the people that live there they say they lost 4 billion dollars from 1980 to 2010 there’s strict pollution standards and oyster restoration efforts have given reason for hope but there’s been some efforts there that have failed and some then that’s kind of a happy story that are beginning to succeed in bringing back the populations of oysters that live in the Chesapeake Bay understanding the rise and the fall of the oyster industry in the Chesapeake Bay as with many other human impacts of the environment involves comprehending the complex interlink systems that comprise Earth’s environment it’s good to think of Earth’s environment as a system with things coming in and out of it and with many interactions happening such as the exchange of matter and energy and information that occurs on a daily basis a system receives inputs of the matter and the energy and the information and processes the inputs and then also produces outputs such as different products or releasing energy such as in the form of heat to help us understand the earth and its ecosystems as a system scientists often divide up the earth or the environment into some different regions these include the lithosphere which is the rock and the sediment the atmosphere which is the air surrounding the planet the hydrosphere which is all the water on earth and the biosphere which is the area of the planet in which life can occur counter I categorizing the systems allows humans to understand Earth’s complexity the systems of the earth involve feedback loops much as maybe you remember in past biology or health classes talking about homeostasis and how your body systems work with feedback loops earth’s ecosystem works much the same way to maintain what’s called a homeostasis or a balanced dynamic equilibrium in a negative feedback loop a system moving in one direction yields output that acts as an input that moves the system in the other direction or the opposite direction so the input and the output pretty much neutralized one another’s effects which actually stabilizes the system for instance a thermostat stabilizes a room temperature by turning the furnace on when the room gets cold and shutting it off when the room gets hot this is also very similar to how your body maintains its temperature if we get too hot our sweat glands pump out moisture that evaporates to cool us down or we move into the shade if we get too cold we shiver creating heat or we move into the Sun in a system stabilized by negative feedback processes that move in opposing directions and equivalent rates so that their effects balance out are set to be in dynamic equilibrium or homeostasis now in a positive feedback this drives

the system further toward an extreme instead of stabilizing it in positive feedback increased output leads to increased input leading to further increased output exponential growth in a population is a good example of this the more individuals there are the more offspring that they have and the more offspring they have well then the more offspring their offspring have if you can get my drift there that it keeps growing uncontrollably and exponentially growing cancer cells are another example of positive feedback loops here’s some diagrams to help show negative feedback and positive feedback this one shows a negative feedback loop for example if we get hot we sweat and sweating cools down the body most systems in nature involve negative feedback also in our body it involves negative feedback as well and this allows them to maintain homeostasis one positive feedback cycle of great concern to environmental scientists today involves the melting of glaciers and sea ice in the Arctic as a result of global warming ice and snow being white reflects sunlight and keep surfaces cool but if the climate warms enough to melt the ice in the snow then darker surfaces of the land and water are exposed and those surfaces then absorb sunlight and warms the surface then causing further melting which in turn exposes more dark surfaces leading to further warming and runaway cycles of positive feedback are rare in nature but they are common in natural systems that have been altered by human impact one of our questions in our chapter asks us but isn’t positive feedback good and negative feedback bad the answer to that frequently asked question is actually no understanding negative and positive feedback in systems can be difficult because the way they name them actually goes against the way that we use those terms in everyday language such as when someone gives you positive feedback it makes you feel good when they give you negative feedback it makes you feel bad but environmental systems and in systems of the body it’s actually just the opposite negative feedback are the ones that resist the change in the systems and thereby enhances the stability of the system typically typically keeping conditions within ranges that are beneficial to life opposing ly positive feedbacks exert destabilizing effects that push conditions to extremes threatening organisms adapted to the system’s normal conditions thus negative feedback environmental systems typically aids living things whereas positive feedback often harms them so really it’s just in the naming not to be confused there environmental systems definitely interact and we think of the Chesapeake Bay with its oyster problem it’s not just a problem of just the Chesapeake Bay let’s think of it as a system with all the areas around it that feed stuff to the system the Chesapeake Bay receives agricultural runoff from six states that neighbor it this contains very high levels of nitrogen and phosphorous it also receives air pollution from fifteen states in what’s called its air shed the runoff area is called its watershed again the air and the pollution it receives from the air is called the air shed here’s some sources of nitrogen and the phosphorus that entered the Chesapeake Bay whether the agriculture from fertilizer and manure from industrial wastewater from urban and suburban fertilizer runoff either way there’s just too much nitrogen and phosphorus too much nitrogen and phosphorus which are important nutrients for life lead to the process called eutrophication this is the process of nutrient / enrichment and blooms of algae and increased production of organic matter and subsequent

subsequent ecosystem degradation for example this is almost like a positive feedback loop here in itself this eutrophication nitrogen and phosphorus entered the Chesapeake Bay from the watershed it causes the phytoplankton to grow phytoplankton are microscopic algae and bacteria so they grow kind of out of control because there’s so many nutrients available for them then they died and they sink to the bottom then that causes an overproduction of bacteria who like to feed on these dead phytoplankton and the actual feeding and the decay of these phytoplankton by the bacteria causes the oxygen to be depleted in the water because decay uses up oxygen well when there’s not enough oxygen fish and other aquatic organisms will either flee the area or they’ll suffocate and die here’s a chart to help us visualize that when there is a lack of oxygen this is called hypoxia there’s that word right here in the chart this water is said to be hypoxic now sometimes it’s just this area here and then that can be called kind of a dead zone whereas the water above it where this decay is not happening there is actually oxygen up there and because more runoff from fresh water is coming in there will be more oxygen at the upper levels here’s a chart showing global hypoxic dead zones nutrient pollution from farm cities and industries has led to more than 400 hypoxic or oxygen-depleted dead zones as we can see the Chesapeake Bay is not the only water body suffering from eutrophication nutrient pollution has led to more than 400 documented hypoxic dead zones including one that actually forms nearby us at the mouth of the Mississippi River each year the increase in the number of dead zones there were actually 162 documented in the 1980s and only 49 in the 90 1860’s reflects how human activities are changing the chemistry of waters around the world let’s now take a look at chemistry and its applications in environmental science understanding matter chemistry and energy will actually help us understand our environments as systems matter is all of the material or the stuff in the universe that has mass and occupies space it said there’s three states of matter which can be solid liquid or gas solids are those items whose particles are very closely compacted liquid the particles are a little further apart so they can slip past one another and gases the particles are spread not very dense at all they’re very spread out therefore they are a gas but all of them have mass and they occupy space or they have volume therefore they are called matter chemistry is the study of the types of matter and their interactions it’s crucial for understanding how for example chemicals affect the health and the wildlife and people pollutants cause acid precipitation synthetic chemicals thin our ozone layer and how gases contribute to global climate change among just the few reasons why we want to understand chemistry when we study science and the environment matter can be transferred from one type of substance into other types but it can’t be destroyed or created this is called the law of conservation of matter and it’s something that happens all the time in nature as matter is transformed from one thing to the next such as say atom of carbon is at one time in a molecule of sugar such as glucose and then

another time is in a molecule of carbon dioxide because the amount of matter stays constant it’s recycled in nutrient cycles and in ecosystems and we can’t simply just wish away pollution or waste we’re stuck with it it’s matter it’s here kind of the basics of chemistry our atoms and elements they’re the building blocks an element is a chemical substance with a given set of properties if you remember studying the periodic table in chemistry the periodic table contains the elements that we know of on earth scientists agree usually that there’s about 92 naturally occurring elements and we’ve even been able to create elements in the lab though some of them don’t exist very long so we say there’s about 20 artificially created elements some examples are nitrogen and phosphorus oxygen carbon and sulfur nutrients are elements that organisms need in large amounts like carbon nitrogen and calcium an atom is the smallest component of an element that would still have the properties of that element in an atoms Center there’s a nucleus which actually includes protons which are positively charged particles and neutrons that are neutral surrounding the nucleus are electrons which are negatively charged particles that are in motion around the nucleus in what are called energy levels the atomic number also used to number elements on the periodic table is actually the number of protons the mass number is actually the protons plus the neutrons sometimes also called the atomic mass electrons really don’t weigh a lot compared to protons and neutrons so often they’re left out of the mass number and when we’re looking for how much an atom weighs mass wise usually we look at just the protons and the neutrons which are again the particles in the nucleus they’re really what contributes to the mass of an atom here’s some ring diagrams of some atoms this one here is carbon that I’m showing you carbons nucleus here has six protons and six neutrons and in the energy levels on the outside are at six electrons when an atom has the same number of protons as it does electrons it’s said to be chemical chemically neutral such as having six protons and six electrons like carbon does here notice I said chemically neutral not necessarily stable but chemically neutral and here’s nitrogen a popular one that we’ve already talked about that’s an important nutrient for all life but in excess amounts can contribute to eutrophication just as phosphorus here also can nitrogen is number seven on the periodic table therefore it’s atomic number is seven it has seven protons seven neutrons in the nucleus and seven electrons phosphorus is number fifteen on the periodic table therefore it has fifteen protons when it’s neutral it has fifteen electrons as well and also with the protons in the nucleus there’s 15 neutrons so 15 protons 15 neutrons and 15 electrons keep in mind there’s not always the same amount of protons as there are neutrons as we’ll see in a bit such as in isotopes isotopes are atoms that have differing numbers of neutrons when you think about it what really defines what an atom is is it’s protons but neutrons can vary if an atom has more neutrons it’s actually going to wait a little bit more than those of its kind that don’t have as many neutrons these are said to be isotopes for instance isotope of carbon carbon

normally contains a mass number of 12 so therefore we call it carbon-12 but when it has more than its usual number of neutrons it can be called carbon 13 when it has an extra Neutron or when it has two extra neutrons it actually then is called carbon-14 those are all isotopes here they show us hydrogen in its different isotopes normally hydrogen doesn’t have any but when it does have an extra Neutron it weighs a little bit more than normal ions are atoms that gain or lose electrons they’re electrically charged and this happens all the time in chemistry I’ve gone back to the previous slide here that shows the pictures of the ring diagrams of our atoms carbon nitrogen and phosphorus and taking a look at carbon in its last energy level it has four electrons this is not a full energy level this energy level could actually hold eight but we’re at four so what carbon often does is bond with other atoms and share electrons in this last energy level we’ll learn later about these types of bonds which are called covalent bonds but the sharing of lek electron out here and using some terms here of course Adams don’t feel but to help us understand it better I’m going to say that by bonding with other atoms it satisfies the need for that atom to have its last energy level full although elements can’t be broken down by chemical reactions some isotopes are radioactive and decay changing their chemical identity as they shed subatomic particles and emit high-energy radiation Radio isotopes decay in the lighter and lighter Radio isotopes until they become stable isotopes which are isotopes that are not radioactive each radio isotope decays at a rate determined by that isotopes half-life which is the amount of time it takes for 1/2 the atoms in a given sample to give off radiation and decay different Radio isotopes have very different half-lives ranging from fractions of a second to billions of years the radio isotope uranium-235 is our society source of energy for commercial nuclear power it decays into a series of daughter isotopes eventually forming lead 207 and has a half-life of about 700 million years these Radio isotopes sometimes are useful in determining how long ago something died or how old a rock bed is atoms bond to form molecules and compounds a molecule is a combination of two or more atoms such as sometimes we say o2 two atoms of oxygen bonded together a compound though is a molecule but it’s composed of atoms of two or more different elements as h2o or water it has the atom oxygen bonded to two hydrogen’s therefore it’s not only a molecule it’s also a compound because it has two different atoms in it using h2o + o2 and co2 are using the chemical formulas of those molecules or those compounds the chemical formula indicates the type and the number of atoms in a molecule or a compound for instance with oxygen here we put its symbol o and then a 2 behind the O to show that there’s two atoms of oxygen in O’Tool in carbon dioxide we use C for carbon its symbol and again oxygen for its symbol and O and then put a tool behind the O because there’s two atoms of oxygen and carbon dioxide if there’s only one atom of an element we just

leave that out and it’s understood that there’s one carbon to two oxygens in carbon dioxide as I said before remember that atoms though they might be neutral are not necessarily stable what they’re looking for again if you remember is that they want their last energy level full now if they only have a first energy level it only takes two electrons to fill that level but in larger atoms that have more than just the first energy level such as in the second energy level they want that one full and that one can hold eight an eight seems to kind of be a magic number for even some of the other energy levels that can hold more than eight electrons but sometimes just having eight there stabilizes that atom atoms that are not stable that are looking to form bonds because their last energy levels are not full of electrons will often form two different kinds of bonds one of those is called ionic bonds sodium chloride or table salt is a good example of an ionic bond in an ionic bond there’s different charges that hold these atoms together sodium has one electron in its last outer level so it’s easy for sodium to kind of give up that last electron to and atoms say like chlorine who might be nearby who has seven in its last level which is only one away from having eight out there so by gaining sodium’s one extra electron chlorine now kind of seems happy because it’s got eight in its outer energy level and sodium because it gave up the extra electron in its last level can now have a new last level and the one that it has is its second level which has eight so both of these atoms are now happy however when you give up negative charges or you receive negative charges it actually causes you yourself to be charged so because the chlorine gained an electron it’s negative the sodium gave up an electron it’s positive because there’s opposite charges with sodium and chloride opposites attract so the sodium and the chlorine atoms will sit next to one another forming what’s called an ionic bond many salts are formed this way in the covalent bond instead of giving up or taking electrons they actually share hence that the prefix Co means to share and valent means the outer level of electrons so as I showed you earlier carbon generally will share with other atoms in four spots because carbon has four electrons already in its last outer level it’s looking to make four bonds out there or to have four more electrons in our example here in the notes they use hydrogen gas or h2 as an example of a covalent bond elements molecules and compounds can also come together in solutions without chemically bonding again chemically bonding is when electrons are shared or stolen or given away which then creates that attraction of the atoms to each other but in solutions there’s actually no chemically bonding or chemical bonding happening here in our atmosphere is a solution formed from items like nitrogen oxygen water vapor carbon dioxide and methane and even those own human blood ocean water plant SAP and metal alloys such as brass are also solutions in any aqueous solution that’s one that contains water a small number of water molecules split apart each forming a hydrogen ion and H+ and a hydroxide ion and Oh H negative the product of hydrogen and hydroxide ion concentrations is always 10 to the negative 14th therefore as one increases the other decreases pure water should contain

equal numbers of those ions each at a concentration of 10 to the negative 7 so we would say that pure water is neutral right here in the middle the chart we’re looking at here is known as the pH scale it quantifies the acidity or the basicity of solutions another word for basicity is also alkalinity and alkaline substance is also known as a basic substance items that are acidic have more hydrogen ions in them and those are the numbers lower than seven in increasing acidity they include normal rain water acidic rain lemon juice stomach acid and car battery acid items that have more hydrogen’s floating around that are not tied up in water add or water molecules can be dangerous as we know when hydrogen ions are floating around and not tied up in water they can go off and bond with other other molecules and this is not good and the same thing with bases faces are higher than the number seven and increasing alkalinity they include sea water soft soap ammonia and sodium hydroxide these have more hydroxide or OAH negative ions and just like hydrogen ions they can be dangerous as well when they’re floating around by themselves and they’re not tied up in water molecules or other molecules they can go off and bond with other things that they shouldn’t be bonding with most biological solutions having this pH between six and eight and substances that are strongly acidic like battery acid or basic like sodium hydroxide are harmful to living things the acidification of soils and water from acid rain and acidic mine drainage are examples of how pH changes caused by human activities can affect ecosystems one thing I’ll also remember is that for each level change of pH it’s a ten times greater amount of hydrogen ions that are present so for instance going from a six to a five a pH of five has ten times more hydrogen ions than six going from a six to a four that’s a hundred times more hydrogen ions going from six to three that’s a thousand times more hydrogen ions and so on and so forth our next topic in the book talks about matter that’s composed of organic and inorganic compounds first we’ll look at the types of compounds that are found in living things living things depend on what are called organic compounds organic compounds are carbon atoms that are bonded together and that these can include other elements like nitrogen and oxygen sulfur and phosphorus and often do carbon can be linked and elaborate chains rings and other structures in organic compounds lack the carbon to carbon bond they can be substances like just plain old water or h2o hydrocarbons these are organic compounds that contain only carbon and hydrogen that are made could be simple as methane here which is ch4 ethane which has two carbons in a chain or it can be very long chains of carbons and hydrogen’s fossil fuels consist of hydrocarbons things like crude oil contain hundreds of types of hydrocarbons these are from living organisms that died long long ago and were subjected to the pressures of the earth to turn them into the crude oil that we use today naphthalene is shown here you probably have smelled naphthalene before it’s also known as mothballs but it is made out of carbons that form rings and also then have the hydrogen surrounding them some compounds form what are called polymers and these are long chains of a

repeated organic compounds polymers play the key roles for some of the building blocks of our lives some things like proteins which make up so much of our bodies are made of polymers the polymers of proteins are called amino acids nucleic acids are also polymers DNA and RNA are nucleic acids carbohydrates sometimes just called carbs are also polymers made out of repeating units of simpler sugars fats or lipids are also essential to life and one of our main big molecules of our body but they are not made out of repeating smaller units though those are not called polymers things like fats oils phospholipids which make up our cell membranes waxes and steroids which form some of our hormones like estrogen and progesterone and testosterone those are lipids but again those are not polymers all of these that we’ve mentioned here proteins nucleic acids carbohydrates and lipids though all do form what are called macromolecules which are the large size molecules that are essential to life so starting with proteins those are long chains of amino acids and comprise most of an organism’s matter they produce tissues provide structural support store energy and transport materials within our body even some of our hormones are made out of proteins some are components of the immune system as well like antibodies they can also serve as enzymes like the enzyme pepsin that’s in your stomach to help you digest proteins enzymes are molecules that catalyze or promote or help along chemical reactions and make them happen faster and more efficiently than the enzyme hadn’t been there animals use proteins to generate skin hair muscles and tendons so many parts of our body in fact DNA codes for the making of proteins cells use information from DNA to string together the polymers of proteins are amino acids to make the proteins that make you that’s how important proteins are to life but DNA actually codes for them nucleic acids speaking of DNA are also polymers they’re long chains of nucleotides a nucleotide contains a sugar if it’s DNA the sugars called deoxyribose linked to a phosphate group and a nitrogen base you may remember the words adenine cytosine guanine and thymine from maybe a past biology class those are the four different nitrogen bases that are in DNA RNA or ribonucleic acid is also a nucleic acid and therefore a polymer DNA though is double-stranded and RNA is only single-stranded genes are regions of DNA that code for proteins and perform certain functions carbs or carbohydrates are another macro molecule and also a polymer it’s repeating unit are simple sugars that are bonded together glucose um very important simple sugar fuel cells and helps us build complex carbohydrates like cellulose cellulose is found in the cell walls of plants and also chitin which forms the shells and exoskeletons of insects and crustaceans cellulose is one of the most abundant carbohydrates on earth glucose also helps us form starch and glycogen plants use starch as their way to store sugar and animals use glycogen but basically what they really are are just strings of glucose the bondings a little bit different in each one but again they’re basically just strings of glucose that repeat again and again and again because they’re polymers the process of digestion helps to break those polymers up so when you eat starches such as in potatoes you actually break that starch down in the process of digestion into its components of glucose and then you use that glucose to fuel cell respiration chemical

reactions in your body lipids those are items that do not dissolve in water they include fats and oils those items have a lot of energy stored in them that we can use and also include waxes which are more of a structural item and steroids and for us steroids would be example like cholesterol and progesterone and testosterone and estrogen which are some of our hormones organisms use cells to compartmentalize macromolecules cells are our most basic unit of organismal organization they’re the simplest component to all living things and can vary so much in their size shape structure and function such as a more of a round or square skin cell versus a very long and pointy nerve cell or an oblong muscle cell they’re classified according to their structure eukaryotes a type of cell that’s included in plants animals fungi and protists contain a membrane and closed nucleus or at least one nucleus some cells have more than one and other membrane-enclosed organelles or cell parts that do specific things prokaryotes those are another type of cell including bacteria and another primitive bacteria called archaea do not contain a nucleus and often lack other membrane-enclosed organelles energy it’s an intangible phenomenon meaning you can’t really hold on to it and sometimes you can’t even see it intangible phenomenon that can change the position physical composition temperature of matter it’s involved in biological chemical and physical processes sometimes energy is called the ability to do work and as we’ve learned before it can be transferred from one form to the next potential energy a type of energy is energy of position kinetic energy another type of energy is energy of motion chemical energy is basically the potential energy held in the bonds between atoms and we can store up chemical energy by the foods that we eat changing potential into kinetic energy can happen because energy can change forms this releases energy and produces motion action and heat so an example of potential energy might be a rock that’s sitting on the hill it’s got a lot of stored energy in it it can change to kinetic energy if it were to roll down the hill and then change into energy of motion potential energy stored in our food becomes kinetic energy when we exercise and release carbon dioxide water and heat as byproducts although energy can change from one form to another it can’t be created or destroyed but just as matter is conserved the total energy in the universe remains constant and thus is said to be conserved scientists have dubbed this principle the first law of thermodynamics for example the potential energy of the water behind a dam will equal the kinetic energy of its eventual movement downstream likewise we obtain energy from the foods that we eat and then expend it in exercise and apply it toward maintaining our body or store it in fat we don’t somehow create additional energy or end up with less energy than the food gives us any particular system in nature can temporarily increase or decrease in energy but the total amount in the universe always remains constant the second law of thermodynamics states that the nature of energy will change from a more ordered state to a less ordered state if no forest counteracts the tendency that is symptoms tend to move toward increasing disorder or what we call entropy for instance a log of firewood a highly organized and structurally complex product of many years of tree growth transforms in a campfire to carbon ash smoke and gases like carbon dioxide and water vapor as well as the light in the heat of the flame with the help of oxygen the complex biological polymers making up that wood are converted into a disorganized assortment of rudimentary molecules and of heat heat and light and energy when energy transforms from that more order to less ordered state it

cannot accomplish tax tasks as efficiently for example the energy available in ash but the less ordered state of wood is far lower than the available energy in a log of firewood which is the more ordered state of the wood living organisms are able to resist entropy though through regular inputs of energy from food sources and photosynthesis but once death occurs and those energy inputs cease an organism undergoes decomp is Bishan and loses its highly organized structure our ultimate source of energy on earth is sunlight it powers most living systems the Sun releases radiation from the electromagnetic spectrum we have a chart here and only a small portion of the electromagnetic spectrum can actually be seen by humans and that’s right here that’s called visible light there’s some organisms such as bees who can see up here into the ultraviolet spectrum and even some that see a little bit lower into the infrared spectrum but what this chart shows us is that there’s so much more energy or radiation coming off of the Sun and what we could even imagine we sort this out by wavelength so we say in the visible light these are the wavelengths that we can actually see or that the cells of our eyes can detect the red orange yellow green blue indigo and violet what we call the rainbow that’s what we see but then there’s much longer wavelengths here like infrared microwaves and radio waves and some of these we can take advantage of like the radio waves and the microwaves and we have the shorter wavelengths up here the x-rays ultraviolet the gamma rays are the shortest and the most highest energy of all of the electromagnetic spectrum so speaking of the ultimate source of energy of sunlight luckily on earth we have organisms who can capture that energy through photosynthesis they have the ability to produce their own food they’re called autotrophs or producers those are organisms like those in the plant kingdom and then algae which are a type of protest and then a type of bacteria called cyanobacteria who get their name from their kind of blue-green color sometimes they’re nicknamed blue-green algae but they are bacteria photosynthesis is the process of turning the sun’s light energy into high-quality chemical energy or making sugar sunlight converts carbon dioxide and water in the sugar moving to lower entropy photosynthesis produces food it occurs in what’s called chloroplasts those are plant structures in the cell that contain the green pigment chlorophyll which is really good at is orbing sunlight it’s a pigment or a protein that the plant makes in order to do that there’s two stages of photosynthesis one is called the light reactions and the other is called the calvin cycle or sometimes also called the dark reactions in the light reaction solar energy or the energy of sunlight splits water and creates high energy molecules that will then be used to fuel the calvin cycle during the light reactions water molecules split and react to form hydrogen ions h+ and molecular oxygen or o2 thus creating the oxygen that we breathe the light reactions also produce small high-energy molecules that like I said are used to fuel our next reactions called the dark reactions or the calvin cycle this is where carbon atoms from carbon dioxide which are what plants take in are linked together to manufacture sugars here we see the photosynthesis chemical reaction and this is a balanced reaction here six molecules of carbon dioxide react with six molecules of water add in the sun’s energy remember this is taking place in a chloroplast and this yields sugar or glucose c6h12o6 plus six molecules of oxygen

this is kind of what I call the fundamental of life here without this reaction happening life on earth would not be like it is or like we know it so in reveal some organisms can do photosynthesis again those were any organism in the plant kingdom cyanobacteria and then a few types of protests like algae they’re able to do photosynthesis but all organisms must do cell respiration so this occurs in all living things organisms use chemical energy created by photosynthesis so basically they take the glucose that was made during photosynthesis and they also breathe in oxygen and do some chemical reactions within the cell part called the mitochondria where they break the high energy chemical glucose bonds and they use that energy to make other chemical bonds or to do other tasks in the body organisms that can only do cell respiration that rely on the feeding on other organisms are called heterotrophs or consumers heterotrophs are in the kingdom Animalia fungi and bacteria archaea and the non algae protests the cellular respiration equation or reaction is actually just the opposite of the photosynthesis equation where we take sugar in the form of glucose which this remember came from photosynthesis and we breathe in oxygen which is also a product of photosynthesis thank you to all of our autotrophs for that and then we make the products of carbon dioxide which you breathe out and then water and energy they just put energy here but it’s actually an energy molecule called ATP or adenosine triphosphate it’s like our fuel and ATP with its chemical bonds has stored energy that we use to fuel different tasks and processes in our bodies so an ecosystem then all organisms and non living entities occurring and interacting in a particular area are called ecosystems so remember it includes the biotic the living entities and the abiotic the nonliving things that interact in an area animals plants water soil nutrients etc air those can all be part of an ecosystem the Chesapeake Bay area that we started off with the story in the beginning about our chapter is actually ecosystem called an estuary an area where fresh water flows into salt water and with their problems with their oyster populations we’ve seen how tightly intertwined the living things are with their physical environment how much they can be affected by things like pollutions and and excess nutrients so the theme here is that energy flows and matter cycles through ecosystems and by saying that we’re holding true to our laws of thermodynamics the Sun energy flows in one direction through ecosystems and energy is processed and transformed into other forms matter is recycled within the systems the outputs though include heat water flow and waste here’s another chart to show us that how producers can capture the energy of the Sun and then give energy to the next level of consumers and then those levels give energy to the next but energy then is lost as heat but remember the same amount of energy remains the same in the universe then we have our decomposers who can help us recycle or cycle nutrients energy is converted to chemical energy in biomass this is called primary production it’s the conversion of solar energy to

chemical energy and sugars by autotrophs during photosynthesis it’s kind of a measure of how much work our producers are doing how much are they providing for us in our ecosystem gross primary production is the total amount of chemical energy produced by autotrophs so it’s a total amount of photosynthesis that they’re doing for us but measured in biomass think of it like money like a paycheck your gross pay is the total amount that you make but of course some taxes have to be taken out of that so what you take home then is the net primary production or your net paycheck so gross primary production in an ecosystem is the total amount of chemical energy made by photosynthesis but of course the plants kind of like taking out taxes they take out what they need for their own cell respiration and then what’s left and is available to the rest of the ecosystem it’s called the net primary production so it’s like your paycheck after taxes so this is the energy remaining after respiration so it equals gross primary production minus cellular respiration and it’s used to generate biomass likely stems and ruts that other heterotrophs can feed upon think of it like a budget how efficient is your budget not all ecosystems or biomes are as efficient there’s one another tropical rainforests and reefs and elbow beds are some of the most efficient ecosystems or biomes on earth meaning they’re autotrophs are doing a lot of photosynthesis to support a lot of biomass and therefore support a lot of heterotrophs swamps are also good estuaries to Savannah’s kind of here in the middle and some of our least productive ecosystems are deserts and Tundras I mean it’s some limiting factors in those areas like temperature it’s too hot in a desert or not enough water or in a Tundra too cold so those are limiting factors that would prohibit photosynthesis therefore making those areas less productive ecosystems though it’s hard to define an actual boundary where one ecosystem begins and the other one ends so often the ecosystems will interact across landscapes or kind of blend into one another or be a transitional zone those are called ecotones a transitional zone between two ecosystems in which elements of each ecosystem mix a bit so landscape ecology is the study of how land kape struck landscape structure affects the abundance distribution and interactions of organisms it’s kind of like sometimes there’s a mix of different ecosystems going on in that landscape because of eco tones it’s useful for studying items like migrating birds fish and mammals and helpful for planning sustainable region regional development often geographic information systems like GIS help us to study landscape ecology for a landscape ecologist a landscape is made up of patches arrayed spatially in a mosaic patches are kind of a mix of ecosystems communities or habitats in an area landscape ecology is of great interest to conservation biologists those are scientists that study the loss protection and restoration of biodiversity populations of organisms have specific habitat requirements and so occupy suitable patches across the landscape if habitat patches are highly fragmented and isolated the populations in those patches may perish accordingly establishing corridors of habitat to link patches is one approach that conservation biologists use to preserve biodiversity in fact in our science

behind the story article of the Chesapeake Bay LAN scape ecology was used to help begin solving that problem here’s an example of some landscape ecology notice there’s some different ecosystems or habitats in here which kind of makes its own little little bit of patches in this area that a conservation biologists may have to study such as the coniferous forest here and the grassland in the river and the freshwater marsh and the lowland broadleaf forests not even to mention the Eco tones or the boundaries that exist between these different ecosystems and all of that makes up what’s called the landscape here’s a question to consider think about the area where you live and briefly describe the region’s ecosystems and how they interact does any water pass from one to the other what are the boundaries like if one ecosystem were greatly modified what impacts on nearby systems might result models help us understand ecosystems a model is a simplified representation of a complicated natural process they help us understand processes and help us make predictions when we’re trying to do the process of science ecosystem modeling constructs and tests models to explain and predict how ecological systems work they’re grounded in actual data and based on hypotheses they’re extremely useful in large intricate systems that are hard to isolate and study for example in studying the flow of nutrients into the Chesapeake Bay and the oyster responses to changing water conditions models were used ecological modelers observe relationships among variables in nature and then construct models to explain those relationships and make predictions ecosystem services sustain our world remember that ecosystem services are the services that ecosystems provide to help keep ecosystems healthy and normally functioning when humans damaged ecosystems then we must devote resources to supply those services ourselves for example if we kill off insect predators farmers then would have to use synthetic pesticides that harm people and Wildlife one of the most important ecosystem services is how nutrients cycle through our environment in intricate ways here’s a list of some ecosystem services that sustain our world regulating oxygen carbon dioxide stratospheric ozone and other at Meerut atmospheric gases cycling carbon nitrogen phosphorus sulfur and other nutrients regulating temperature and precipitation providing habitat for organisms to breed feed rest migrate in winter storing and regulating fresh water supplies protecting against storms floods and droughts filtering wastes and recovering nutrients and controlling pollution controlling crop pests with predators and parasites producing fish game crops nuts and fruits that we eat supplying lumber fuel metals fodder and fiber providing recreation such as ecotourism fishing hiking birding hunting and kayaking and providing even just aesthetic artistic educational spiritual and scientific amenities all of those are ecosystem services that sustain our world so back to the ecosystem service of nutrient cycling nutrients move through our environment in complex ways number matter can’t be created or destroyed just move from one form to the next and matter is continually circulated in an ecosystem and is one of our important ecosystem services this cycling of matter or cycling of nutrients are called biogeochemical cycles it involves two main types of pools a source and a sink nutrients and other materials move

from one pool or reservoir to another remaining in each reservoir form varying amounts of time that’s called the residence time the dinosaur the grass the cow and your body are all reservoirs for carbon atoms when a reservoir releases more materials than it accepts it’s called the source and when a reservoir accepts more materials than it releases it’s called the sink here is a chart to help us visualize that the rate at which materials move between the two reservoirs the source and the sink is called the flux and it can change over time and be impacted upon by humans the water cycle affects all other cycles it’s essential for biochemical reactions and it’s involved in nearly every environmental system in cycle water cycle can also be called the hydrologic cycle it’s the flow of liquid and gaseous and solid water through the environment more than 97% of our water is in oceans and less than 1% is readily available in fresh water some of it it’s it’s tied up in glaciers and frozen but less than 1% is readily available to us as freshwater the cycle is powered by the movement of water by evaporation which is when water that’s liquid becomes a gas and transpiration when liquid water is released into the atmosphere as water vapor by plants and by precipitation when water returns to the Earth’s surface in the form of precipitation like rain and snow water can have areas where it’s stored infiltration is when it soaks down through rock and soil to recharge aquifers which are underground reservoirs of sponge-like regions of rock that hold groundwater the water table is the uppermost level of groundwater held in an aquifer and these are places that we drill our wells to to take advantage of this fresh water source some water in aquifers can be very ancient and be held there for thousands of years here’s a picture to help us see the water cycle so we can say the abiotic reservoir of water is surface and atmospheric water it enters the food chain during precipitation and plant uptake it’s recycled by transpiration and returned to the abiotic world by evaporation and runoff here’s a picture of what transformation looks like as water moves up the tiny passages within plants as it reaches the little pores on the leaves it will be released molecule by molecule in the process called transpiration here’s another chart to help us see the water cycle humans can have an impact on the water cycle like damming rivers slowing water movement and then increasing evaporation by the removal of vegetation that increases runoff in erosion and then that decreases infiltration and transpiration over drawing surface and groundwater for agriculture industry and domestic uses lowers water tables and emitting air pollutants that dissolve in water and changes the nature of precipitation and decreases cleansing or the making of acid rain carbon is also cycled in nature remember that carbon forms essential biological molecules through photosynthesis producers move carbon from the air and the water to organisms then respiration returns carbon back to the air in the water if you don’t remember make sure you go back to the equations of photosynthesis and cell respiration oceans are our second largest reservoir of carbon oceans can absorb carbon from the air land and from

organisms decomposition returns carbon to the sediment and that’s our largest reservoir of carbon ultimately though it can be converted into fossil fuels here’s a chart to help us understand the carbon cycle the abiotic reservoir once again is in the atmosphere as carbon dioxide it enters the food chain by photosynthesis it’s recycled during cell respiration and decomposition and also returned to the abiotic world by respiration and combustion humans of course can have an impact on the carbon cycle just like we do on the water cycle by burning fossil fuels we put more carbon back into the air from the ground it’s said that since the mid 1700s people have added over 276 billion tons of carbon dioxide to the atmosphere cutting forests and burning fields moves carbon from organisms to the air and today’s atmospheric carbon dioxide reservoir is the largest than it’s been in the past 800,000 years or so and the driving force behind anthropogenic global climate change the nitrogen cycle nitrogen also cycles as we learned earlier nitrogen is an important nutrient that all living organisms need it’s in our proteins our DNA our RNA it’s essential for plant growth all organisms need it unfortunately there’s there’s a lot of nitrogen around us but we just can’t get at it in the form that it’s in it’s in the form of end to just end two molecules and it takes a lot of energy to break up the nitrogen bond between n – that’s called denitrifying lightning can do it in nature and lightning storms can actually add nitrogen to the environment and humans have found a synthetic way to do it to put nitrogen into fertilizer but we need a little help from our bacterial Kingdom in order to do much more in nature to become biologically available inert nitrogen gas or n2 has to be fixed or combined with hydrogen in nature to form ammonia or nh3 whose water-soluble ions of ammonium nh4 plus can be taken up by plants again nitrogen fixation can be accomplished by the intense energy of lightning strikes or by particular types of nitrogen fixing bacteria that inhabit the top layer of soil these bacteria live in a mutualistic relationship with many types of plants including soybeans and other legumes providing them nutrients by converting nitrogen to a usable form other types of bacteria and then perform a process called nitrification converting ammonium ions first into nitrate ions no2 and then into nitrate ions no.3 now it’s in a form that plants can actually use plants can take up the nitrate ions and then make them available to the rest of the ecosystem here’s a chart to help visualize this again the abiotic reservoir is nitrogen in the atmosphere it enters the food chain by nitrogen fixation by soil and aquatic bacteria it’s recycled by decomposing and by nitrifying bacteria and returns to the abiotic by denitrifying bacteria here’s a picture of some roots of some legumes where nodules of these nitrogen fixing bacteria live here’s another chart to visualize the nitrogen cycle historically nitrogen fixation was a bottleneck meaning there is a lot available in the atmosphere but only limited amounts were fixed to be made useful to ecosystems but with industrial fixation where humans can fix nitrogen

on a massive scale synthetically we’ve added so much nitrogen to our ecosystems and have really altered our nitrogen cycle on earth this overwhelms nature’s denitrification abilities meaning it’s hard for organisms like the bacteria that can put it back to the environment to keep up excess nitrogen then as we learned at the beginning of the chapter this great nutrient leads to hypoxia in coastal areas because of eutrophication nitrogen based fertilizers stripped the soil of other nutrients thereby reducing soil fertility burning forests and fossil fuels leads to acid precipitation as greenhouse gases and also creates chemical or photochemical smog the phosphorus cycle another one of nature’s important nutrients phosphorus generally is found in rocks there’s really not much in the atmosphere but weathering or water dissolving phosphorus of rocks is what makes phosphorous available to the living components of the ecosystem once plants take up the phosphorus then it’s available to the rest of the ecosystem remember phosphorus is a key component of cell membranes RNA DNA and other biochemical compounds so it is one of those important nutrients that all living things need here’s a chart to visualize our phosphorus cycle the abiotic reservoir is rocks minerals and soil enters the food chain by erosion from water and uptake by Prince its recycled by decomposing bacteria and fungi and return to the abiotic by loss to ocean sediment humans impact the phosphorus cycle much like they impact the nitrogen cycle by adding this stuff to our fertilizers and then fertilizing lawns and farmlands and then it enters ecosystems by runoff and then again leads to eutrophication wastewater containing detergents also releases phosphorus into our waterways here are some ways to tackle nutrient enrichment and would require diverse approaches by reducing fertilizer use on the farms and lawns that would cut down on these nutrients changing the time of fertilizer applications to minimize rainy season runoff by managing manure applications to farmland by our growing vegetation buffers around streams to trap nutrients and sediment runoff constructing wetlands to filter stormwater and runoff by restoring wetlands of long waterways improving sewage treatment technologies upgrading stormwater systems to capture runoff and by reducing fossil fuel combustion all of these can be methods to tackle all these nutrients that are being added to our ecosystems here’s a cost chart the cost per pound of reducing nitrogen inputs into the Chesapeake Bay looks like doing things like restoring and constructing wetlands and making buffers and tilling our fields differently those are some of the things that would cost the least moistures like the ones in the Chesapeake Bay helped to filter out nutrients in water and make the water more healthy so aquaculture annoys that are native to their areas and adding them back is another strategy and is actually one of the strategies that has helped the Chesapeake Bay turn its problems around other items like stormwater retrofits and stormwater management are a little more expensive so I wing the issues again something to think about with this nutrient pollution and its financial impacts who do you believe should be responsible for addressing these problems should environmental policies on this issue be developed and then enforced by state

governments by federal governments both or neither so back to the Chesapeake Bay problem collaborative efforts of Concerned Citizens advocacy organizations the EPA and state governments has helped after 25 years of failed Pollution Control agreements and 6th hall six billion dollars spent on cleanup efforts the Chesapeake Bay Foundation sued the EPA Environmental Protection Agency in 2009 stating they really weren’t doing their job and enforcing these pollution and control agreements in late 2010 then they established the pollution budget in these states around the Chesapeake Bay and reducing nutrient and sediment inputs into the bay and limiting harvests of oysters crabs and fish are already yielding some evident improvements to the bays health if you read the science behind the story in this chapter you’ll read about David Schulte from the US Army Corps of Engineers who helped to bring about some of the biggest helps to this problem they realized that some of the efforts to bring back wasters were not working because the reefs that the oysters grew on were being destroyed moisture is really rely on connecting themselves to other oysters which then over time builds up reefs with the dead oysters and the shells and such so his plan was to pick some areas and then build some reefs and then put in some native oysters and then cut down on the amount of harvesting of the oysters in that area and the data was pretty remarkable in how fast moistures were able to grow on those human-made reefs and it’s helping the water quality already in these areas and they’re very hopeful that these solutions will really pay off in conclusion life interacts with its abiotic environment in ecosystems through which energy flows and materials are recycled understanding biogeochemical cycles is crucial to help us understand ecosystems and humans are changing the ways that those cycles functions sometimes actually a great amount for the worst understanding energy energy flow and chemistry increases our understanding of organisms and how environmental systems function and in thinking in terms of systems can help teach us how to how to avoid disrupting Earth’s processes and to mitigate any disruptions we caused and once again this last chart to remind us how energy flows through ecosystems our ultimate source of energy the Sun light and how nutrients cycle keeping true to the laws of thermodynamics their matter and energy cannot be created or destroyed