Life on Earth

Think WAAAAAY Back… With your group, write the 7 properties of life Take turns... Person 1: write down 1 property of life, then pass the paper to Person 2 Person 2: write down another property of life, then pass the paper to Person 3

What is life? All living things have these 7 properties: Made of a cell(s) Have DNA Able to reproduce Grow & develop Obtain & use energy Respond to stimuli Maintain homeostasis If matter does not have all 7 properties, then it is not living!!

Why Can Life Exist on Earth?? Distance from the Sun Earth’s atmosphere Presence of Water Gravitational Pull

Our planet is the perfect average distance from the sun! REASON #1 Our planet is the perfect average distance from the sun!

Our Earth Earth is the 3rd closest planet to the sun (93 million miles away) Earth’s mass has been most recently calculated at 5.98 × 1024 kg (*you obviously can’t measure this!) It has continents! Inner core temp: 13,040 degrees F

Earth & Sun Perfect average distance from the Earth So humans don’t burn or freeze to death! Sun fuels all life processes All organisms get their energy from the sun….somehow! Most common way is by photosynthesis

Remember Photosynthesis…? CO2+H2O+ENERGY (sunlight)  O2 + C6H12O6 Sun’s energy is transformed into chemical energy If there is no sun, there is no ENERGY for photosynthesis to occur therefore…we could not survive!

Also, without the Sun, rain would be next to impossible, because the water cycle could not occur!

Earth has a very unique atmosphere! REASON # 2 Earth has a very unique atmosphere!

4 Spheres of Earth Lithosphere- earth’s crust (soil, rocks, minerals) Hydrosphere- earth’s water Atmosphere- the gases in the air Biosphere- all living things

Earth’s Atmosphere Sustains Life Earth’s atmosphere is a combination of gases: Nitrogen, Oxygen, and Argon remain constant; while there are varying trace amounts of CO2 and water vapor

What’s In Air: 78.08% Nitrogen (N2) Oxygen (O2) 20.95% Argon (Ar) 0.93% Neon, Helium, Krypton, other 0.0001%

What makes these gases important? Oxygen is critical, but so are the other gases in the atmosphere! Gases absorb heat from the sun, which warms the atmosphere, creating the “greenhouse effect” (Without these gases, the surface of earth would be about -16˚F!)

Our atmosphere= Our protection! The atmosphere protects us from meteors! Small meteorites burn up in the atmosphere before reaching Earth. Those that do hit the surface and create an impact crater are quickly eroded due to weather and the evidence is lost. The moon has no atmosphere… every meteorite coming towards it will hit it! Moon Earth

REASON # 3 Water exists here!

Speaking of Water…. Our planet is dominated by water- more than 70% of the Earth’s surface is covered with this simple molecule The hydrosphere is estimated to contain about 1.36 billion km3 of water If all our planet’s ice melted, sea-level would rise by about 70 meters!

CO2+H2O+ENERGY (sunlight)  O2 + C6H12O6 Water is required for photosynthesis to occur!

REASON # 4 GRAVITY!!!

Earth’s Gravity What is gravity? the tendency of objects with mass to accelerate towards each other The Sun’s gravity holds our solar system together Objects with more mass= more gravity Earth’s mass creates an ideal gravitational pull http://www.exploratorium.edu/ronh/weight/