Earth & Space

2. Disappearance of about 70% of marine species
5. Hard solid organs that form part of a skeleton.
6. When the organism's original bones are replaced by minerals which form a rock-like material.
9. The star around which the earth orbits.
10. Disappearance of more than 50% of fish, sponges and corals
11. A long and distinct period of history.
13. Describes any flow of electric charge through a gas, liquid or solid.
15. Solid inorganic substances of natural occurrence.
16. Are experts in the study of fossils.
17. The process of change by which an organism or species becomes better suited to its environment.
18. Disappearance of 96% marine species and 75% of land species
19. A group of living organisms consisting of similar individuals capable of exchanging genes or interbreeding.

1. Disappearance of about 50% of animal species
3. Is formed by the deposition of material at the earth's surface and in bodies of water.
4. Happen when lava and gas are discharged from a volcanic vent.
7. Any remains or trace of an organism in the earth's crust.
8. Also known as K/T.
9. Made up of sedimentary deposits with the same characteristics.
12. A widespread and rapid decrease in the amount of life on earth.
14. The gradual destruction of something by natural forces.
16. The exertion of force upon a surface.