2. What does it mean to be alive? Investigation 2.2 Is it Alive? Uses Energy Exchanges gasses Responds to Stimuli Reproduce Grow & Develop

4. So, what planets have these vital conditions/characteristics? EARTH

10. The Sun’s proximity (distance from Earth) to Earth makes Earth a good candidate for supporting life. At this distance, Earth receives just the right amount of radiant energy. The main factor affected by this radiant energy is TEMPERATURE. Earth’s temp. is 130 o F – 160 o F

11. Earth has an abundance of the element Oxygen. Oxygen is a component of many, many vital compounds organisms use to carry out life functions. One such vital compound is H 2 O

12. Earth has plenty of liquid water Earth’s temperature range allows for liquid water to exist over much of the planet. All organisms on Earth use water in unique ways

14. Earth is just right Mercury, Venus, and Mars are too hot or too cold for liquid water to exist. (PROXIMITY to the SUN)

15. The human body is 60% to 75% water. Liquid water is used to transport food and nutrients where they need to go, inside and outside of cells. Why liquid water is important

16. Water is a good solvent. A solvent is a substance that is capable of dissolving another substance. Importance of water

17. Filters Radiation Protects Earth from Collisions Traps Heat (protects from freezing temperatures, especially at night)

18. Nitrogen (N 2 ) gas makes up about 78% of Earth’s atmosphere. Nitrogen is a vital element for living things. An atmosphere is a layer of gases surrounding a planet or other body in space.

20. The atmospheres of Venus, Earth, and Mars were formed in similar ways, so we might expect them to contain similar elements. Comparing atmospheres

21. Changing the atmosphere Through photosynthesis, life on Earth has actually changed the planet’s atmosphere.

22. Gravity holds our atmosphere to Earth. Without it, our atmosphere would float away. Gravity keeps atmospheric gasses in propper layers. Heavy gasses near the surface, lighter gasses away from the surface. Gravity keeps things grounded (dirt, trees, water, you)