1. Earth as a System Open and Closed Systems The Gaia Hypothesis The Web Of Life

2. Open and Closed Systems By now you should realize that Earth is a large system of interacting parts, or cycles By now you should realize that Earth is a large system of interacting parts, or cycles A system is a set of parts that work together A system is a set of parts that work together Open systems can either lose or gain parts Open systems can either lose or gain parts In Closed systems all parts exist in precise amounts. No mass can be lost or added, but energy can pass through its boundary. Essential parts are recycled/ reused. In Closed systems all parts exist in precise amounts. No mass can be lost or added, but energy can pass through its boundary. Essential parts are recycled/ reused. Both types of systems require energy Both types of systems require energy

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

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

5. Open and Closed Systems (cont’d) The Earth is a closed system The Earth is a closed system As we’ve studied, there are several interdependent cycles at work As we’ve studied, there are several interdependent cycles at work They are all driven by the Sun – our main energy source They are all driven by the Sun – our main energy source We must never forget that we live in a closed system – we risk upsetting the balance nature has provided if we irresponsibly use Earth’s resources We must never forget that we live in a closed system – we risk upsetting the balance nature has provided if we irresponsibly use Earth’s resources

6. The Gaia Hypothesis Developed by James Lovelock while working for NASA Developed by James Lovelock while working for NASA He proposed that the Earth functions as a single living organism He proposed that the Earth functions as a single living organism Over 4.6 billion years Earth (Gaia) has developed into a self-evolving, self- regulating and self-sustaining system Over 4.6 billion years Earth (Gaia) has developed into a self-evolving, self- regulating and self-sustaining system

7. The Gaia Hypothesis (cont’d) The name Gaia is after the ancient Greek goddess The name Gaia is after the ancient Greek goddess Both living and dead organisms and the inorganic (non –living) material in the hydrosphere, lithosphere, and atmosphere are all part of a dynamic (constantly changing) system that makes up the biosphere Both living and dead organisms and the inorganic (non –living) material in the hydrosphere, lithosphere, and atmosphere are all part of a dynamic (constantly changing) system that makes up the biosphere Gaia represents all of the processes on the planet working together Gaia represents all of the processes on the planet working together

8. The Gaia Hypothesis (cont’d) The composition of the hydrosphere, lithosphere, and atmosphere and related cycles are the result of constant adjustments and interventions by Gaia to ensure her own survival. The composition of the hydrosphere, lithosphere, and atmosphere and related cycles are the result of constant adjustments and interventions by Gaia to ensure her own survival.

9. The Gaia Hypothesis (cont’d) Two ways Gaia accomplishes this include: 1. Allowing evolution so species may meet new environmental changes 2. Ensuring a great diversity of life

10. The Gaia Hypothesis (cont’d) Gaia has been able to survive cataclysmic events like asteroid collisions Gaia has been able to survive cataclysmic events like asteroid collisions Lovelock believes that the effect of humans will not endanger Gaia Lovelock believes that the effect of humans will not endanger Gaia He believes the real danger is for the human beings living on Gaia as the result of the way she reacts to our environmental assaults He believes the real danger is for the human beings living on Gaia as the result of the way she reacts to our environmental assaults

11. Ecosystems: The Web of Life The sun is the original source of energy in virtually all ecosystems. The sun is the original source of energy in virtually all ecosystems. Producers (plants) convert the light energy into chemical energy, storing it in their cells. Producers (plants) convert the light energy into chemical energy, storing it in their cells.

12. Ecosystems: The Web of Life When primary consumers (herbivores) eat the producers, the energy changes into a form that can be stored in animal cells. When primary consumers (herbivores) eat the producers, the energy changes into a form that can be stored in animal cells. Secondary consumers (carnivores) transform the energy once again. Secondary consumers (carnivores) transform the energy once again. Decomposers may occupy several positions in the pyramid, both receiving energy from decaying plants and animals and supplying it to detrivores and fungus-eaters. Decomposers may occupy several positions in the pyramid, both receiving energy from decaying plants and animals and supplying it to detrivores and fungus-eaters.

14. Activity 8 1. Please read pages 67 – 73 in your textbook. 2. Record definitions for any vocabulary in bold print. Try to put the definitions in your own words. 3. Using examples explain the difference between an open and closed system. 4. Why is Earth a closed system? 5. In your own words, explain the Gaia Hypothesis. Use examples to demonstrate your understanding. 6. Create an original chart/ diagram that show how energy is transferred in an ecosystem. Clearly define all key terms. Your chart/ diagram should be easy to read and understand. It should also clearly demonstrate your understanding of this process

15. References Corbin, B. et al (2000). Global connections. Oxford Press, Ont. Microsoft Corporation (1999). Encarta Encyclopedia: The Food web.