our standards, the early
earth was not user
friendly. The surface
was hot, with volcanic
eruptions releasing carbon
dioxide, water vapor, and
nitrogen into the early
atmosphere. It was lifeless for many millions of years. Rain fell, and water
began the work of erosion, wearing away the
igneous rocks and slowly
dissolving some of the chemicals on the rock surfaces. Rivers
carried the chemicals into the seas, and the
chemicals were mixed
and stirred in the water.
No one knows for certain how
life began. We know that all terrestrial life has strings of
DNA, which are long chains of self-replicating molecules that
encode information. We know that life forms (except for viruses)
are made up of cells, which are tiny containers that hold the
DNA and other chemicals that
make up the cells. The
early life forms were single cells.
This chapter will have
some information about cells
so that you can start life
on your own world!
Your group will do this in class:
- discuss your first life forms and how they live in your climates
- Sketch your unicellular organisms
- write a description of how life arose on your planet.
- write descriptions of your planet's first life forms.
Homework: Bring to class next session:
- The written description of how life arose.
- The written description of your life forms.
- Your computer drawn, or drawn and scanned, pictures of your
first life forms.