1. Earth: The Fragile Miracle
Conditions for Life

2. The Goldilocks Zone
Earth’s life-sustaining conditions are possible because of its position in the solar system
It is not too hot and not too cold – if the Earth was any closer or further away from the Sun, the planet could not support life

3. Other Life Sustaining Conditions
Earth’s rotation on its axis and orbit around the Sun helps distribute heat evenly around the planet
Earth’s magnetic field protects the planet from deadly radiation and particles
Earth’s gravitational field holds the atmosphere in place preventing oxygen, nitrogen, and carbon dioxide from escaping into space

4. Four Conditions for Life
Stable Temperature Range
The Importance of Water
The Importance of Gases
The Role of the Atmosphere

5. Stable Temperature Range
A stable temperature range (-50 to about +50 degrees Celsius) allows life to thrive – the average temperature has been between degrees Celsius for 3.5 billion years
The greenhouse effect allows for heat in the atmosphere (carbon and water vapor) to be re-radiated back to Earth
Without proper water and carbon, the earth would be -73 degrees C.

6. The Greenhouse Effect
Plants play a significant role in creating a stable temperature through releasing water vapor and oxygen by the processes of photosynthesis and transpiration
Dark areas of vegetation absorb heat from the sun’s rays and limit the albedo effect – heat being reflected back into space

7. Photosynthesis

8. The Importance of Water
First water likely came from volcanic activity – water collected on the cooling surface and as vapour in the atmosphere creating the water cycle
Biologists believe earth first began in the oceans – blue-green algae
Oceans cover 2/3 of the Earth – absorbs heat and distributes it around the world and controls our weather patterns and climates
Helps distributes nutrients to plants and other organisms
No living this consists of less than 50% water
Water is the metabolizing agent that allows plants and animals to dissolve minerals and nutrients to create energy

9. The Importance of Gases
78% nitrogen, 21% oxygen, carbon dioxide 0.03% - quite different than other planets in the solar system
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

10. The Role of the Atmosphere
Layer of gases about kms thick – very thin compared to size of Earth
Helps maintain a consistent temperature
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

11. The Four Spheres
Lithosphere – earth’s crust (soil, rocks, and minerals)
Hydrosphere – earth’s water
Atmosphere – the gases in the air
Biosphere – all living things (plants, bacteria, animals)

12. Biosphere Encompasses all living organisms including humans
Divided into separate but interdependent units called ecosystems – well defined habitats hosting systems of interacting organisms
Nutrient Cycle - Continuation of life depends on the constant recycling of chemical ingredients called nutrients (Example: plants and animals die and decompose)

13. Biosphere – The Carbon Cycle
The movement of carbon from the atmosphere into plants, animals, and the soil and then back again
Plants take carbon dioxide from the atmosphere to produce food through photosynthesis and release oxygen – animals breath oxygen and eat plants
Dead animals and plants decay and return carbon to cycle
Over production of carbon dioxide from factories and burning rainforests causes climate change

14. Biosphere – Nitrogen Cycle
Most powerful element in the Earth’s atmosphere
Microscopic bacteria live on the roots of certain plants known as legumes and converts nitrogen to ammonia and nitrates which the plant absorbs and converts to protein – food production

15. Biosphere – Oxygen Cycle
Oxygen produced by the respiration of plants – 90% of oxygen used is replaced by algae in oceans
Oxygen created by photosynthesis

16. Biosphere – Water Cycle
Water must be recycled through the atmosphere and back to the Earth’s surface
Most from evaporation – some from transpiration; water drawn by plants and released through their leaves
Groundwater dissolves nutrients in the soil