1.3 Energy & Equilibrium

Kristin PageIB ESS2015-2016

Significant Ideas

• The laws of thermodynamics govern the flow of energy in a system and the ability to do work.

• Systems can exist in alternative stable states or as equilibria between which there are tipping points.

• Destabilizing positive feedback mechanisms will drive systems towards these tipping points, where as stabilizing negative feedback mechanisms will resist such changes.

Applications and Skills

• Explain the implications of the laws of thermodynamics to ecological systems.

• Discuss resilience in a variety of systems.

• Evaluate the possible consequences of tipping points.

Knowledge and Understanding:• Know the first and second laws of thermodynamics • Give examples of the first and second laws of

thermodynamics in ecological systems• Distinguish between stable equilibrium and steady

state equilibrium• Distinguish between positive and negative feedback

loops• Explain how positive and negative feedback loops

lead to a system being stable or becoming unstable• Discuss factors that affect the resilience of a system.• Explain what is meant by tipping point and how the

resilience of a system affects the tipping point

ECOSYSTEMS • Ecosystems involve interrelationships among

climate, geology, soil, vegetation, and animals. These components are linked together transfers and transformations of energy and or matter.

• Two basic processes occur in ecosystems1. Cycling of matter: only a finite amount

of nutrients on Earth so must be recycled2. Flow of energy: all energy originates

from the sun and is used by plants in photosynthesis and converted to a form usable by all other organisms http://easyscienceforkids.com

CYCLING MATTER

https://en.wikipedia.org/

There are only finite amounts of nutrients available on the earth, therefore they must be recycled in order to ensure the continued existence of living organisms.

FLOW of ENERGYSolar energy enters Earth's systems as radiant energy. This energy is used by plants for food production. As heat, it warms the planet and powers the weather system. Eventually, the energy is lost into space in the form of infrared radiation. Most of the energy needed to cycle matter through earth's systems comes from the sun.

ECOSYSTEMS & ENERGY• Thermodynamics is the study of

the energy transformations that occur in a system.

• 2 Laws of thermodynamics: • 1st Law of Thermodynamics:

Principle of Conservation of Energy• Energy cannot be created

or destroyed, it can only change forms

• Therefore the total energy in an isolated system (universe) is constant

ECOSYSTEMS & ENERGY• 2nd Law of Thermodynamics• In an isolated system, the total amount of entropy

(disorder) will tend to increase.• More entropy = more disorder• Energy conversions are not 100% efficient• Energy is lost to the environment in the form of heat

http://goose.ycp.edu/~kkleiner/envbio/envimages/L12_Ecosystems/foodchain2.jpg

SUN ENERGY

ECOSYSTEMS & ENERGY• Due to the 2nd Law of Thermodynamics, energy is not equally

passed through a food chain• Plants only convert 1-2% of the energy they receive into stored

sugars• In general only about 10% of the energy is passed from 1 trophic

level to the next (the rest is used in metabolism, to do work, an as heat loss)

• Less and less energy is available as you move up a food chain

http://images.tutorvista.com/

ECOSYSTEMS & ENERGY

• Pyramid of energy is always upright because at each transfer about 80 - 90% of the energy available at lower trophic level is used up to perform metabolic activities and as heat lost to the environment.

• Only 10% of the energy is available to next trophic level (as per Lindemann's ten percent rule).

EFFICIENCY OF AN ECOSYSTEM• Efficiency is the comparison of the amount of work or energy

done to the amount of energy that is consumed• (multiply by 100% to turn into %)• We use efficiency in ESS to discuss how efficient parts of the

system are• For example: Is it more efficient to eat a plant or an animal?• Due to the loss of heat as you move up a food chain it is

more efficient to eat a plant because there is less energy loss• In the example below, the carnivore is very inefficient as

1000J of sunlight started but only 0.1 joule is available to the lion

http://images.tutorvista.com/

STEADY STATE EQUILIBRIUMEquilibrium: • A state of balance between parts of a system• There are fluctuations in a system, however most

systems return to a balanced state after a disturbance.

Steady-state equilibrium • allows an open system to go to back to balance after

disturbance

NEGATIVE FEEDBACKHomeostasis The property of a system to maintain a stable, constant condition.Negative Feedback• The way living systems maintain homeostasis.• Involves a sequence of events that will cause an effect

that is in the opposite direction to the original stimulus and thereby brings the system back to equilibrium.

• Examples:• A population of insects may remain the same overall

even though individuals are born or die. • Human body temperature; we get cold we shiver to

warm up, we get hot we sweat to cool down

STATIC EQUILIBRIUMStatic Equilibrium• no changes over time• no inputs or outputs to system• non-living (cannot occur in living systems since there is

always an exchange of energy and matter)• when a disturbance occurs a new equilibrium is

reached • ex: rock formations over time, bottle sitting on table

Unstable or Stable Equilibrium

• Stable Equilibrium: System returns to original state after disturbance• Unstable Equilibrium: System returns to new

equilibrium after disturbance.

http://www.physicalgeography.net/

FEEDBACK LOOPS• Systems are constantly undergoing change and

responding to change• There are 2 possible types of feedback mechanisms:• Positive Feedback Loops: • Changes bring about a new steady-state level• Destabilize a system

http://all-geo.org/

http://www.thwink.org/

http://www.tokresource.org/

Positive Feedback Loop

FEEDBACK LOOPS• Negative Feedback Loops: • Return system to original state• Stabilize a system

http://carignanapbio.weebly.com/

http://physwikiproject.wikispaces.com/

PREDATOR PREY RELATIONSHIPSPredator Prey relationships are usually controlled by negative feedback where:• Increase in Prey Increase in Predator • Decrease in Prey Decrease in Predator • Increase in Prey and so on in a cyclical manner

Resilience & Tipping Points• Resilience: the ability of a system to “bounce back” after

a disturbance• Low resilience: system does not return to original state• Generally high resilience is a good thing – ex a forest

returns after a fire• However sometimes it is a bad thing – ex antibiotic

resistant bacteria has high resilience• Tipping Point: when a system is pushed past the point of

returning to it’s original state

Ecosystem Resilience• Many factors affect how resilient an ecosystem may be

including;• Species Diversity: the more different species the more

resilient it is• Habitat diversity: the more complex the interactions the

more resilient• Genetic diversity: the more variety within a population the

more resilient• Size of ecosystem: generally larger ecosystems are more

resilient• Climate: arctic- harsh climate, little sunlight, cold vs

rainforest – warm, lots of rainfall• Faster species reproductive rate (r-strategists recolonize

faster than K-strategists)

Tipping Points• Involve positive feedback loops • Once tipping point is reached there is a quick change to

the system• Changes are long-lasting• Changes are difficult to reverse• There is a time lag between the events driving the

change and the evidence of the impact

Tipping Point Examples• Eutrophication of a Lake (Gulshan)• Nutrients are added to lake (fertilizers)• Algal blooms occur due to increased nutrients • Sunlight is blocked from reaching lake floor• Oxygen levels in lake decrease• Living things die due to lack of oxygen• Decomposers thrive due to dead material• Decomposers release more carbon dioxide into lake

as the decompose • Oxygen levels drop further

Tipping Point Examples• Species Extinction (Sunda Rhinoceros

Bangladesh)• Poaching for horns & medicines• Habitat loss• Current population is between 50-60 in

a small region of Java

Tipping Point Examples

Tipping Point Examples

http://oceantippingpoints.org/

Tipping Point Examples

http://futurehumanevolution.com/

HOMEWORK1.3 To Do Questions pp 36, 37, & 40