Life in the Universe

http://www.flickr.com/photos/kaibara/2234750993/

Alien life

forms?

Life has changed over time –

evolved.

New species have evolved…while some organisms have

hardly changed at all.

Stromatolite

Ancient trilobites & their present-day cousins, the chitons

Cockroaches Jurassic & Modern

Natural variation

Environmental Pressure & Survival of the Fittest

Horses – Eocene to modern

Requirements of life, (as we know it)

• Carbon-based molecules

• Energy source

• Water

DNA

Present in all of Earth’s life

forms

The Goldilocks Principle

“This porridge is too hot.”

“This porridge is too cold.”

“This is just right.”

Why does life exist on Earth ?

• Life began here • Life traveled here from other worlds - exogenesis

Exogenesis – Did life travel here from a distant world?