Evolution of the Atmosphere
It's really tricky to teach this topic because this is
not agreed amongst scientists. In my view, the impression given by the
syllabus is wrong since it implies that plants evolved before animals - it
looks more likely that the converse is true. Still, do your best with the
syllabus! Dr E
Check
Across: 1. Hydrocarbon present in early atmosphere. 5. Opposable digit. 8. and 25
across. Substance present in the early atmosphere which readily condensed to form covering to 2/3 of the Earth's surface. 10.
Allotrope of oxygen which protects Earth's surface from ultraviolet radiation. 11. Reactive gas which is thought to have made many of the first plants extinct. 14. and 17 down. Much of atmospheric oxygen was present in the early atmosphere as this compound. 15. Period of time. Earth's current age is roughly 4.5 billion of this unit. 16. Adjective describing paper with parallel marks to aid writing. 18. Sound produced when a test tube of hydrogen is ignited. 21. Sea creature related to starfish, often almost spherical in shape. 22. Sleeve. (It's hard to make a crossword using only Earth's Atmosphere vocabulary!) 23. Sedimentary rock which "mopped up" much of the carbon dioxide in the early atmosphere. 24. See 6 down. 25. See 8 across.
Down: 2. Form of energy present in large quantities 4.5 billion years ago which prevented life from evolving. 3. Inert gas produced from 20 down by bacteria. 4. and 12 down. Inert elements present in small quantities in the atmosphere. 6. Much of the carbon from carbon dioxide became incorporated into these useful sources of chemical energy. 7. These structures produced the early atmosphere. 9. Gaseous region of the Earth. 12. See 4 down. 13. Element comprising the majority of today's atmosphere. 17. See 14 across. 19. First organisms to evolve. 20. Compound present in the early atmosphere containing nitrogen.
