Earth & Space

3. Disappearance of more than 50% of fish, sponges and corals
6. Describes any flow of electric charge through a gas, liquid or solid.
10. The star around which the earth orbits.
11. Disappearance of about 70% of marine species
12. Also known as K/T.
13. Solid inorganic substances of natural occurrence.
16. When the organism's original bones are replaced by minerals which form a rock-like material.
19. Happen when lava and gas are discharged from a volcanic vent.

1. The exertion of force upon a surface.
2. Disappearance of 96% marine species and 75% of land species
4. A widespread and rapid decrease in the amount of life on earth.
5. Are experts in the study of fossils.
6. The gradual destruction of something by natural forces.
7. A long and distinct period of history.
8. Made up of sedimentary deposits with the same characteristics.
9. Is formed by the deposition of material at the earth's surface and in bodies of water.
14. The process of change by which an organism or species becomes better suited to its environment.
15. Disappearance of about 50% of animal species
17. Any remains or trace of an organism in the earth's crust.
18. Hard solid organs that form part of a skeleton.
20. A group of living organisms consisting of similar individuals capable of exchanging genes or interbreeding.