1. Earth: a Unique Planet for Human Life

2. Characteristics of Our Planet
Temperature
Water
Atmosphere
Magnetic Field
Gravity
Energy
Nutrient Cycles

3. Unique Characteristics
Earth has a perfect balance of these characteristics which supports life as we know it.
An earth bias exists as life on earth has adapted and evolved to survive on our planet.

4. Conditions for Life on Earth

5. 1.A Constant and Relatively Mild Temperature
-50 to about +50 degrees Celsius
Average temp. has been between degrees C for 3.5 billion years
The Greenhouse effect allows for heat in the atmosphere (carbon and water vapor)
Without proper water and carbon, the earth would be -73 degrees C.

6. Temperature Earth’s temperature is unique as it is very stable.
Average fluctuations are degrees celsius
Average temperature is 15 degrees celsius.

7. Temperature Continued
This means that organisms do not have to adapt to extreme fluctuations.
For Example:
Mercury fluctuates from -184 to +465
Why is temperature significant?

8. Earth’s Temperature At 100 degrees water boils and evaporates to gas.
Below zero it freezes.
Water does not exist on any known planet in liquid form.

9. Water -Water is essential to life.
-It is the medium for which biochemical reactions occur.
-Water is needed to transport Nutrients/waste, in and out of cells.
-When water freezes it floats, insulating the bottom from harsh temperatures, keeping it liquid.

10. Atmosphere
What is unique about Earth’s atmosphere?

11. Atmosphere Continued
Earth’s atmosphere contains all the necessities for life.
Nitrogen 78%, oxygen 20%, and 2% composed of carbon (0.04%) and others.
Only atmosphere that has oxygen.

12. Atmosphere Continued
Ozone in the atmosphere filters out radiation from the sun.
Greenhouse gases act as a blanket to keep some heat in and stabilize temperature.
Plays a major role in earth’s life cycles.

13. The Real Greenhouse Effect

14. 2. The Importance of Water
First water likely came from volcanic activity and the vapors released
Biologists believe earth first began in the oceans – blue-green algae
Oceans trap heat and distribute it around the world (2/3 of the earth)
No living thing consists of less than 50% water
Water is the metabolizing agent that allows plants and animals to dissolve minerals and nutrients to create energy

15. Photosynthesis

16. 3.The Importance of Gases
78% nitrogen, 21% oxygen, carbon dioxide 0.03%
The plants have removed most of the carbon dioxide that originally existed and produced lots of oxygen
Without life on earth, carbon dioxide would increase
The production of carbohydrates, fats, and proteins require oxygen, carbon, and nitrogen atoms from the atmosphere, and hydrogen from water

17. 4. The Role of the Atmosphere
Layer of gases about kms thick
Helps maintain a consistent temp.
Shields earth from collisions with cosmic particles (meteors)
Oxygen levels at 21% allow for life, if they drop, animal life would not be possible, if it exceeds 25% most plants would be consumed by fire
Oxygen is produced by plants and consumed by animals and the burning of plants and fossil fuels

18. Gravity and Magnetic Field
Earth has a magnetic field towards the poles.
This deflects solar radiation and meteors.
Gravity is essential because it keeps our atmosphere in place.

19. Energy All life needs an energy source.
This could be from direct sun or through chemical reactions which are helped by sunlight(photosynthesis).

20. Nutrient Cycles
Because the earth is made of tectonic plates there are significant cycles which return nutrients to life on earth.
Examples: Volcanic activity, Tsunamis.
Rock, water, atmospheric cycles.

21. Questions Time to spin, time to orbit, and gravity.
How would these factors affect life?

22. Planet Task Using a combination of resources, answer the following:
Describe the physical characteristics of your planet
Describe how your planet is similar and different to earth.
Explain the challenges to life on your planet using your knowledge from a variety of resources
Based on this, determine whether your planet is habitable