The History of Earth

2. time of ancient life.
3. a scientist who studies the history of life on Earth through the fossil record.
6. this period known as the “age of fishes”.
9. the period just before the proliferation of complex life on Earth.
10. this is when almost all marine organisms came into existence as evidenced by abundant fossils.
13. It is a system of chronological measurement that relates stratigraphy to time.
14. time of recent life.
18. the period where life first formed on Earth, archea and bacteria.
19. it is known as the age of reptiles.
24. The largest intervals of geologic time.
25. a scientist who studies the solid, liquid, and gaseous matter that constitutes Earth and other terrestrial planets, as well as the processes that shape them.
27. without it life could not exist on land because of harmful ultraviolet radiation.
28. of life forms occur and fill the various ecological niches available on Earth.
29. it gave rise to mammals.
30. the earliest well developed circulatory system (vascular plants).

1. This period brought the emergence of terrestrial life.
4. It is also sometimes called the “ age of flowering plants”.
5. It is the subdivision of eons.
7. this era is known as the “age of mammals”.
8. this is the period of visible life where rapid expansion and
9. time, also known as the “time of hidden life”.
11. a porous shell containing a membrane that provided an environment for embryo.
12. the formation of organic deposits of coal in plant debris formed the world’s first extensive coal deposits.
15. Warm -- moist climate conditions contributed to lash vegetation and dense swampy forests.
16. it gave rise to the dinosaurs.
17. a primitive armoured fish with a cartilage skeleton.
20. This period marks the earliest appearance ofvertebrates and the jawless fish known as Agnatha.
21. time of middle life.
22. It appeared on Earth at some time between 3.9 billion years ago.
23. it was largely responsible for the demise of the great coral reefs, jawless fishes and trilobites.
26. A dramatic climatic shift may have been partially triggered the assembly of smaller continents into Pangea.