Why Environmental Systems?

Today we will determine the components of a system, and how systems comprise the planet. We will also begin to explore how our actions can alter the different systems around us. Directions:You and your partner will need to read through the slides and fill out the packet. Stop rolling your eyes it’s not that bad. You can watch the videos, but not too loudly…you don’t want to be “that guy” ;)

Why Environmental Systems?

• SYSTEM: an assemblage of parts and their relationship forming a functioning entirety or whole.

• During the 1970’s, British chemist James Lovelock and American biologist Lynn Margulis came up with the GAIA HYPOTHESIS: That the world acts like a single biological being made up of many individual and interconnected units ( A SYSTEM ).

• Gaia was the Greek Earth goddess

Watch this creepy person tell you about Gaia

• http://www.youtube.com/watch?feature=player_embedded&v=VjLC3GjFMv0

figure 1. A systematic view of the Earth’s biological and chemical components

The Components• The Earth’s systems comprise interactions between the

living ( Biotic ) and non-living (Abiotic ) constituent parts.

• As in any system, these interactions involve INPUTS, processing of the inputs to create OUPUTS.

• Even if we look at the starting point of all food chains on Earth, photosynthesis and conversion of light energy to stored chemical energy in the leaf, this to can be viewed as a system component within a bigger system.

So Photosynthesis comprises inputs, a process and outputs

• But photosynthesis is also a component in a larger system. A food chain the initial

• light energy gets processed and converted into chemical energy (food) that is passed along the system.

• Yet if you take each of the organisms in the diagram above and place them in individual plant pots or cages at a zoo and the system breaks down: the interactions between the components are what make the system not the components themselves

1.1.2 Types of Systems

• Systems can be thought of as fitting into one of three types: Open (exchange matter and energy with its surroundings), Closed and Isolated

• Open Systems: exchange matter and energy with its surroundings.

Open Saysa Me!• Most systems are open, including ecosystems.

– In forest ecosystems plants fix energy from light entering the system during photosynthesis. Nitrogen is fixed by soil bacteria.

• Herbivores that live within the forest canopy may graze in adjacent ecosystems such as a grassland, but when they return they enrich the soil with feces.

• After a forest fire top soil may be removed by wind and rain. Mineral nutrients are dissolved out of the soil and transported in ground water to streams and rivers.

Open System

• Open system models can even be applied to the remotest oceanic island - energy and mater is exchanged with the atmosphere, surrounding oceans and even migratory birds.

• It is important to remember that if we are thinking in the terms of systems, then each component of a system is surrounded by a larger environment. – A single tree ( a system in its own right ) within a forest

system exchanges energy and material with the surrounding forest.

Closed Systems: exchange energy but not matter.

• Closed systems are extremely rare in nature. No natural closed systems exist on Earth but the planet itself can be thought of as an “almost” closed system.Light energy in large amounts enters the Earth’s system and some is eventually returned to space a long wave radiation (heat).

Biosphere 2• Biosphere 2 was a human attempt to create a habitable

Closed system on Earth. • Build in Arizona at the end of the 1980’s Biosphere 2 was

intended to explore the use of closed biospheres in space colonization.

• Two major “missions” were conducted but both run into problems.

• The Biosphere never managed to produce enough food to adequately sustain the participants and at times oxygen levels became dangerously low and needed augmenting.

http://youtu.be/bPK05evoFHw (lady)

Biosphere II

PS: Closed Systems

• Closed Systems do not occur naturally on Earth. BUT all the Global Cycles of Matter approximate to closed systems.

• Water Cycle• Nitrogen Cycle

• Closed systems!!!!!

Isolated Systems: An isolated system exchanges neither matter nor energy.

• These do not exist naturally. • Though it is possible to think of the entire

Universe as an isolated system.

Things to Know

Easter IslandGaia HypothesisBiosphere II experiment

(might want to look into those)

1.1.3 Energy In Systems

• Energy in all systems is subject to the Laws of Thermodynamics

• According to the First Law of Thermodynamics: Energy is neither created or destroyed.

• What this really means is that the total energy in any system including the entire universe is constant all that can happen is that the form the energy takes changes. – This first law is often called the law of conservation of

energy.

• In the food chain above the energy enters the system as light energy, during photosynthesis it gets converted to stored chemical energy (glucose).

• It is the stored chemical energy that is passed along as food. No new energy is created it is just passed along.

Even if we look at the sunlight falling on Earth not all of it is used for photosynthesis.

• 30% is reflected, around 50% is converted to heat, and most of the rest powers the hydrological cycle - rain, evaporation, wind, etc. Less than 1% of incoming light is use for photosynthesis.

Second Law of Thermodynamics

• The Second Law of Thermodynamics states that the entropy of an isolated system not in equilibrium will tend to increase over time.

• What this really means is that the energy conversions are never 100% efficient: – When energy is transformed into work, some

energy is always dissipated as waste heat.

• If you examine the food chain again in terms of the second law then: when the lion chases the zebra, the zebra attempts to escape changing the stored chemical energy in its cells into useful work.

• But during its attempted escape some of the stored energy is converted to heat and lost from the food chain.

This process can be summarized by a simple diagram showing the energy input and outputs.

• The Second Law can also be thought off as a simple word equation:

ENERGY = WORK + HEAT (and other wasted energy)

So what does the term ENTROPY mean?

• Entropy refers to the spreading out or dispersal of energy. • Using the above example the energy spreads out - the useful energy

consumed by one level is less than the total energy at the level below - energy transfer is never 100% efficient.

• Depending on the plant their efficiency at converting solar energy to stored sugars is around 2%. Herbivores on average only use around 10% of the total plant energy they consume the rest is lost in metabolic processes and a carnivores efficiency is also only around 10%.

• So the carnivores total efficiency in the chain is 0.02 x 0.1 x 0.1 = 0.0002• This means the carnivore only uses 0.02% of incoming solar energy that

went into the grass. The rest of the energy is dispersed into the surrounding environment.

1.1.5 Equilibria

• Open systems tend to exist in a state of balance: Equilibrium.

• Equilibrium avoids sudden changes in a system, though this does not mean that all systems are none changing.

• If change exists it tends to exist between limits. • We can therefore think of equilibrium states in two

ways STATIC and “STEADY STATE”.• Static Equilibrium is where the components of a

system remain constant over a long period of time.

Static Equilibrium

• Possibly the best example of static equilibrium in the environmental system in which we ourselves have to survive is the oxygen content of the atmosphere.

Huh?• Around 4 billion years ago there was very little

oxygen in the atmosphere.

Why? Because: Our planet was void of life.

• Then life appeared and importantly photosynthesizing life, first cyanobacteria (bacteria with chlorophyll) and later plants.

• Both of which produce molecular oxygen a waste product.

• As the oxygen levels rose so a new type of organism appeared that could use the external oxygen in respiration - animals - and so the Oxygen cycle was born.

• Eventually over time a balance was achieved in the level of atmospheric oxygen and for the last 2 billion years, plants and animals have held the oxygen level stable at 21% of the atmosphere.

Steady State equilibria

• Steady State equilibria: this is a much harder concept to define and there are still arguments for what a dynamic equilibrium really is.

• The best way to think about it is that a system is in a steady state because the inputs and outputs that affect it approximately balance over a long period of time.

http://app.discoveryeducation.com/searchChemistry Connections: Introduction to Chemical Equilibrium Systems

• An example of this can be seen in a classic study of the populations of Snowshoe Hares and Lynx in Canada. http://www.britannica.com/blogs/2011/06/rise-fall-canada-lynx-snowshoe-hare/

• As the population of the Lynx rises the Hare population falls this is then followed by a fall in the Lynx population which in itself is followed by a rise in the Hare population etc. etc.

Feed Back Systems

• Systems are continually affected by information they have to react to from both within and outside.

• Two simplistic examples, if you start to feel cold you can either put on more clothes or turn the heating up.

• The sense of cold is information putting on clothes is the reaction. Secondly if you feel hungry, you have a choice of reactions that you can take to this “information”

Feedback Loop.

• Natural systems act in exactly the same way. • The information starts a reaction which in turn

may input more information which may start another reaction.

• This is called a Feedback Loop.

Negative Feedback

• Negative Feedback: this tends to damp down, neutralize or counteract any deviation from an equilibrium, and promotes stability.

Using the example of the Snowshoe Hare / Lynx population cycle presented in the previous slides

• When Hare the population is high, there is surplus food for the Lynx so their numbers go up.

• This puts a pressure on the Hare population as more are eaten and their numbers fall. Less food for the Lynx so they start to starve and their numbers fall.

• Fewer Lynx means fewer hares are eaten and their numbers start to go back up. And so it continues as a loop.

• Explaining it in words is very cumbersome so the diagram is a much better way.

Positive Feedback

• Positive Feedback amplifies or increases change; it leads to exponential deviation away from an equilibrium.

• An example of this is the possible effect that rising global temperature could have by adding more water vapor to the atmosphere.

• Water is a powerful greenhouse molecule trapping heat in the atmosphere. If there is a global temperature rise more water will evaporate trapping more heat making more water evaporate trapping more heat and on and on.

1.1.6/7 Transfers & Transformations

• Both Material and Energy move or flow through ecosystems.

• A transfer is when the flow does not involve a change of form.

• A transformation is a flow involving a change of form. • Both types of flow use energy, transfers being simpler

use less energy and are therefore more efficient than transformations.

http://sciencebitz.com/wp-content/uploads/2009/05/transfers.swf

Transfers can involve:

• The movement of material through living organisms (carnivores eating other animals)

• The movement of material in a non-living process (water being carried by a stream)

• The movement of energy (ocean currents transferring heat)

Transformations can involve:

• Matter (glucose converted to starch in plants)

• Energy (Light converted to heat by radiating surfaces)

• Matter to energy (burning fossil fuels)

• Energy to matter (photosynthesis)

1.1.8 Flows and Storages• Both energy and matter flows (inputs and

outputs) through ecosystems but at times is also stored (stock) within the ecosystem:

The Biogeochemical Cycle

• The Biogeochemical Cycle illustrates the general flows in an ecosystem.

• Energy flows from one compartment to another. E.g. a food chain.

• But when one organism eats another organism the energy that moves between them is in the form of stored chemical energy: Flesh

The Biogeochemical Cycle

• Energy Flows through an ecosystems in the form of carbon–carbon bonds within organic compounds. These bonds are broken during respiration when carbon joins with oxygen to produce carbon dioxide. Respiration releases energy that is either used by organisms (life processes) or is lost as heat.

The origin of all the energy in an ecosystem is the sun and the fate of the energy is

eventually to be released as heat

• In the diagram above the flow of energy is shown by the red arrows.

• Unlike energy MATTER cycles through the system as minerals (blue arrows).

• Plants absorb mineral nutrients from the soil. These nutrients are combined in to cells.

• Consumers eat plants and other consumers digest the minerals they contain and re-combining them in cells.

• Eventually decomposers break down dead organic matter (DOM) and then return the minerals to the soil.

• These minerals may betaken out of the soil quickly by plants or can eventually through geological processes become locked within rocks until erosion eventually returns them to new soil.

• The geochemical cycles illustrate the flows and storage of energy and matter: The carbon cycle shows the flow of both where as the other geochemical cycles e.g. nitrogen only show the flow and storage of matter.

• In both cases though the direction of the flow - producer to consumer, and the magnitude - loss of material up a food chain, amount of carbon dioxide moving from respiration and combustion to the atmosphere,can be described.