Curiously enough, we haven't yet found life outside Earth, although we did find organic molecules on asteroids that crashed into our planet. But astronomers, such as Carl Sagan, argue that there must be a lot of life outside Earth, outside our Solar system.
Some say that "life" is the higher form of existence of matter, higher than physical or chemical forms.
Essential characteristics of life, as we know it on Earth, seems to be: 1) cellular form, 2) genes within cells responsible for reproduction.
"Life" is the cycle of existence of an organism from birth to death.
Two main species that we know and that are alive are plants and animals. Their common characteristics are:
- growth, development
- ability to obtain food for sustaining itself
"Thinking " of one sort or another is present only with animals.
- What is life? A lecture by Jeremy England, 2014