The History of Earth

7. Event, it was largely responsible for the demise of the great coral reefs, jawless fishes and trilobites.
9. time scale, It is a system of chronological measurement that relates stratigraphy to time.
10. time of middle life.
11. Period, Warm -- moist climate conditions contributed to lash vegetation and dense swampy forests.
16. time, also known as the “time of hidden life”.
18. time of recent life.
20. it gave rise to mammals.
21. Eon, the period just before the proliferation of complex life on Earth.
24. a primitive armoured fish with a cartilage skeleton.
26. Era, this era is known as the “age of mammals”.
27. 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.
30. Period, This period marks the earliest appearance ofvertebrates and the jawless fish known as Agnatha.
31. of life forms occur and fill the various ecological niches available on Earth.

1. a scientist who studies the history of life on Earth through the fossil record.
2. time of ancient life.
3. Eon, this is the period of visible life where rapid expansion and
4. Mesozoic Era, it is known as the age of reptiles.
5. Eon, the period where life first formed on Earth, archea and bacteria.
6. Age, the formation of organic deposits of coal in plant debris formed the world’s first extensive coal deposits.
8. bacteria, It appeared on Earth at some time between 3.9 billion years ago.
12. It is the subdivision of eons.
13. Period, this is when almost all marine organisms came into existence as evidenced by abundant fossils.
14. Era, It is also sometimes called the “ age of flowering plants”.
15. it gave rise to the dinosaurs.
17. The largest intervals of geologic time.
19. Period, A dramatic climatic shift may have been partially triggered the assembly of smaller continents into Pangea.
22. egg, a porous shell containing a membrane that provided an environment for embryo.
23. Period, this period known as the “age of fishes”.
25. Layer, without it life could not exist on land because of harmful ultraviolet radiation.
28. the earliest well developed circulatory system (vascular plants).
29. Period, This period brought the emergence of terrestrial life.