Existence of Life Class Notes

Goldilocks & the 3 bears ○ Remember the story of Goldilocks & the 3 bears. ○ Think about what the words “just right” meant.

○ What are some conditions that are “just right” on Earth to allow life to exist?

Cornell Notes Title: Existence of Life Topic/Objective: TEKS 7.9A Analyze the characteristics of objects in the Solar System that allow life to exist. Essential Question 1: What characteristics are needed for life to exist?

Just Right…. ○ A habitable planet has abiotic factors (non-living) and characteristics that are just right for allowing life to exist. ○ Earth is the only known planet at this time.

What makes Earth “just right”? ○ Draw and label a diagram of the planets going across your paper in order with the sun on the left. Sun MercuryVenus Earth MarsJupiter Saturn Uranus Neptune Earth is in just the right location for life to exist (not too hot, not too cold)!

Characteristics that Allow Life to Exist: 1. Temperature ○ Life is limited to a temperature range of -15°C to 115°C. ○ Because of its distance from the sun, Earth has a temperature range of 0°C to100°C, which allows life to exist. ○ The length of day and night also contribute to temperatures that can sustain life.

2. Presence of Liquid Water ○ Earth’s temperature range allows water to exist in liquid form. ○ 0°C is the freezing point of water and 100°C is the boiling point of water. ○ Water is regularly available. ○ Landforms allow water to run from high to low elevations and replenish as the seasons change.

3. Composition of Atmosphere ○ The Earth’s atmosphere thickness traps heat & protects it from the Sun’s harmful UV radiation. ○ It also protects it from small to medium sized meteorites. ○ It contains gases including nitrogen, oxygen, argon, & carbon dioxide. (NOArCo2)

4. Energy Source ○ With a steady input of either light or chemical energy from the sun, cells can perform the chemical reactions necessary for life (photosynthesis). ○ These give us food sources including plants and animals.

5. Nutrients ○ All solid planets and moons have the same general chemical makeup so nutrients are present. ○ Planets with a water cycle or volcanic activity can transport and replenish the chemicals required by living organisms (vitamins).

Essential Question 2: Why is Earth the perfect location for life to exist? ○The temperature is not too hot and not too cold (length of day and night) ○Water can exist in liquid form, many sources available ○Atmosphere has needed gases for living things ○Sun provides energy so plant cells can carry out photosynthesis ○Earth has nutrients necessary for life to exist

Review Questions 1.What characteristics are needed for life to exist? 2.Why is Earth the perfect place for life to exist?