Extraterrestrial Life

1
Extraterrestrial Life!?
2
How do we know if something is alive?
3
1. Characteristics of Life
a) Living things take in nutrients. b) Living
things use the nutrients for energy. c)
Living things produce waste. d) Living things
reproduce.
4
2. Why is water so important?
There are many chemical changes that happen
inside every living things body. These
processes need a way to move around. Liquids
work best for chemicals to move around in. Water
seems to be the best liquid for these movements
and chemical changes.
5
3. Why is carbon the basis of Earth life?

• a) Carbon forms four bonds, so it can make lots
  of combinations.

6
Why is carbon the basis of Earth life?

• b) Carbon can form long chains.
• c) Long chains and lots of
• combinations are needed to
• form the thousands of
• chemicals found in living things.

Fatty Acid
DNA
Protein Molecule
7
4. How could we tell if something is alive?

• a) Test for changes in the chemicals around them.
• b) Be careful not to contaminate the sample.
• c) Check for temperature changes.
• d) Look for changes in numbers.

8
5. Are there other options besides water and
carbon?

• a) We have not found any alternatives that could
  work as well as water does.
• b) Silicon might be an alternative to carbon so
  maybe there are silicon based life forms