Geologic Time Scale

2. An organism that has an exoskeleton that consists of three lobes that run the length of the body.
4. Blue-green algae thought to be one of the earliest forms of life on Earth.
6. The longest subdivision based upon the abundance of certain fossils.
7. A process by which organisms with characteristics that are suited to a certain environment have a better chance of surviving and reproducing than other organisms that do not have these characteristics.
11. Means "recent-life" and began about 65 million years ago continuing today.
12. The change of species through time and is recorded in the geologic time scale through fossils.
14. Characterized by the types of life existing world wide at the time.
15. One giant landmass of all continents and broke apart at the end of the Paleozoic era.

1. The longest part of Earth's history.
3. Is marked by major, striking, and world wide changes in the types of fossils present.
5. Means "middle-life" and was a time of many changes on Earth.
8. A group of organisms that normally reproduce only with other members of their group.
9. The division of Earth's history into time units cased on the life-forms that lived during certain periods.
10. Characterized by differences in life-forms and differences vary between continents.
13. Began about 544 million years ago and ended about 248 million years ago.