Earth as a SystemEarth as a SystemOpen and Closed Open and Closed SystemsSystemsThe Gaia HypothesisThe Gaia HypothesisThe Web Of LifeThe Web Of Life

Open and Closed Open and Closed SystemsSystems By now you should realize that Earth is a By now you should realize that Earth is a

large system of interacting parts, or cycleslarge system of interacting parts, or cycles A A systemsystem is a set of parts that work together is a set of parts that work together Open systems Open systems can either lose or gain partscan either lose or gain parts In In Closed systemsClosed systems all parts exist in precise all parts exist in precise

amounts. No mass can be lost or added, but amounts. No mass can be lost or added, but energy can pass through its boundary. energy can pass through its boundary. Essential parts are recycled/ reused. Essential parts are recycled/ reused.

Both types of systems require energyBoth types of systems require energy

Open and Closed Open and Closed Systems (cont’d)Systems (cont’d) The Hydrosphere is an open The Hydrosphere is an open

systemsystem

Earth is an example of a Earth is an example of a closed system.closed system.

Open and Closed Open and Closed Systems (cont’d)Systems (cont’d) The Earth is a closed systemThe Earth is a closed system As we’ve studied, there are several As we’ve studied, there are several

interdependent cycles at workinterdependent cycles at work They are all driven by the Sun – our They are all driven by the Sun – our

main energy sourcemain energy source We must never forget that we live in a We must never forget that we live in a

closed system – we risk upsetting the closed system – we risk upsetting the balance nature has provided if we balance nature has provided if we irresponsibly use Earth’s resources irresponsibly use Earth’s resources

The Gaia HypothesisThe Gaia Hypothesis Developed by James Lovelock while Developed by James Lovelock while

working for NASAworking for NASA He proposed that the Earth functions He proposed that the Earth functions

as a single living organismas a single living organism Over 4.6 billion years Earth (Gaia) has Over 4.6 billion years Earth (Gaia) has

developed into a self-evolving, self- developed into a self-evolving, self- regulating and self-sustaining systemregulating and self-sustaining system

The Gaia Hypothesis The Gaia Hypothesis (cont’d)(cont’d)

The name Gaia is after the ancient Greek The name Gaia is after the ancient Greek goddessgoddess

Both living and dead organisms and the Both living and dead organisms and the inorganic (non –living) material in the inorganic (non –living) material in the hydrosphere, lithosphere, and hydrosphere, lithosphere, and atmosphere are all part of a dynamic atmosphere are all part of a dynamic (constantly changing) system that makes (constantly changing) system that makes up the biosphereup the biosphere

Gaia represents all of the processes on Gaia represents all of the processes on the planet working togetherthe planet working together

The Gaia Hypothesis The Gaia Hypothesis (cont’d)(cont’d)

The composition of the The composition of the hydrosphere, lithosphere, and hydrosphere, lithosphere, and atmosphere and related cycles atmosphere and related cycles are the result of constant are the result of constant adjustments and interventions by adjustments and interventions by Gaia to ensure her own survival.Gaia to ensure her own survival.

The Gaia Hypothesis The Gaia Hypothesis (cont’d)(cont’d)Two ways Gaia accomplishes this Two ways Gaia accomplishes this

include:include:

1.1. Allowing evolution so species may Allowing evolution so species may meet new environmental changesmeet new environmental changes

2.2. Ensuring a great diversity of lifeEnsuring a great diversity of life

The Gaia Hypothesis The Gaia Hypothesis (cont’d)(cont’d) Gaia has been able to survive Gaia has been able to survive

cataclysmic events like asteroid cataclysmic events like asteroid collisionscollisions

Lovelock believes that the effect of Lovelock believes that the effect of humans will not endanger Gaiahumans will not endanger Gaia

He believes the real danger is for He believes the real danger is for the human beings living on Gaia as the human beings living on Gaia as the result of the way she reacts to the result of the way she reacts to our environmental assaultsour environmental assaults

Ecosystems: The Web Ecosystems: The Web of Lifeof Life The sun is the original source of The sun is the original source of

energy in virtually all ecosystems. energy in virtually all ecosystems. Producers (plants) convert the Producers (plants) convert the

light energy into chemical energy, light energy into chemical energy, storing it in their cells. storing it in their cells.

Ecosystems: The Web Ecosystems: The Web of Lifeof Life When primary consumers (herbivores) eat When primary consumers (herbivores) eat

the producers, the energy changes into a the producers, the energy changes into a form that can be stored in animal cells. form that can be stored in animal cells.

Secondary consumers (carnivores) transform Secondary consumers (carnivores) transform the energy once again.the energy once again.

Decomposers may occupy several positions Decomposers may occupy several positions in the pyramid, both receiving energy from in the pyramid, both receiving energy from decaying plants and animals and supplying it decaying plants and animals and supplying it to detrivores and fungus-eaters. to detrivores and fungus-eaters.

Activity 8Activity 81.1. Please read pages 67 – 73 in your textbook.Please read pages 67 – 73 in your textbook.2.2. Record definitions for any vocabulary in bold print. Record definitions for any vocabulary in bold print.

Try to put the definitions in your own words.Try to put the definitions in your own words.3.3. Using examples explain the difference between an Using examples explain the difference between an

open and closed system. open and closed system. 4.4. Why is Earth a closed system?Why is Earth a closed system?5.5. In your own words, explain the Gaia Hypothesis. In your own words, explain the Gaia Hypothesis.

Use examples to demonstrate your understanding.Use examples to demonstrate your understanding.6.6. Create an original chart/ diagram that show how Create an original chart/ diagram that show how

energy is transferred in an ecosystem. Clearly energy is transferred in an ecosystem. Clearly define all key terms. Your chart/ diagram should be define all key terms. Your chart/ diagram should be easy to read and understand. It should also clearly easy to read and understand. It should also clearly demonstrate your understanding of this processdemonstrate your understanding of this process

ReferencesReferences

Corbin, B. et al (2000). Global Corbin, B. et al (2000). Global connections. connections. Oxford Press, Oxford Press, Ont.Ont.

Microsoft Corporation (1999). Microsoft Corporation (1999). Encarta Encarta Encyclopedia: Encyclopedia: The Food The Food webweb. .