Lecture24_Biosphere3

Lecture24_Biosphere3 - EAS 1600 Introduction to...

Info iconThis preview shows pages 1–4. Sign up to view the full content.

View Full Document Right Arrow Icon
EAS 1600 Introduction to Environmental Sciences ____________________________ Class 27 - The Biosphere: Part 3 Metabolic Processes Evolution of Biosphere and Earth System ________________________________ In this lecture we discuss the various chemical pathways or strategies organisms use to survive, and the role these pathways play in the Earth System. Biogeochemical cycle involving N ¾ photosynthesis: 5CO 2 + 5H 2 O + 5 h ν Æ 5“CH 2 O” + 5O 2 ¾ denitrification: 4HNO 3 + 5"CH 2 O” Æ 2N 2 + 5CO 2 + 7H 2 O ¾ nitrogen fixation: 2N 2 + 6H 2 O Æ 4NH 3 + 3O 2 ¾ nitrification 4NH 3 + 8O 2 Æ 4HNO 3 + 4H 2 O Biogeochemical cycle involving C ¾ photosynthesis: CO 2 + H 2 O + h ν Æ “CH 2 O” + O 2 ¾ respiration “CH 2 O” + O 2 Æ CO 2 + H 2 O Biogeochemical cycle involving S (simple) ¾ photosynthesis: 2CO 2 + H 2 S + 2H 2 O+ h ν Æ 2"CH 2 O” + H 2 SO 4 ¾ sulfate reduction H 2 SO 4 + 2"CH 2 O” Æ 2CO 2 + H 2 S + 2H 2 O Biogeochemical cycle involving S (not simple) ¾ photosynthesis: 2CO 2 + 2H 2 O + h ν Æ 2“CH 2 O” + 2O 2 ¾ sulfate reduction H 2 SO 4 + 2"CH 2 O” Æ 2CO 2 + H 2 S + 2H 2 O ¾ H 2 S oxidation in atmosphere can you write down the reaction that is needed to balance the cycle? Now let’s try to understand: 1. How these various metabolic processes evolved on the earth; and 2. How they, in turn, influenced the evolution and development of the earth system itself.
Background image of page 1

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
Geologic Time: Eons Æ Eras Æ Periods Æ Epochs From Monroe, J.S., and R. Wicander, Physical Geology: Exploring the Earth , West Publishing, New York, 639 pp, 1992. Hadean Interesting Aside: Earth formed: ~ 4.6 bya Humans appeared: ~ 2 mya Industrial Revolution: ~ 250 ya If 4.6 billion years were equivalent to 1 day, then Earth formed: 1 day ago Humans appeared: 37 seconds ago Industrial Revolution began: 4.7 milliseconds ago In the span of those 4.7 mseconds, we have increased CO 2 by 25%, CH 4 by 100%, . .. (Over Pre-Industrial levels) Human population has increased by about 600%. How do we know what occurred and when? ¾ Relative dating - principal of superposition in stratigraphy ¾ Absolute dating - radiometric dating The Hadean — The 1 st Billion Years Evolution of basic physical environment ¾ Hard to document since oldest rocks are 3.6 billion years old ¾ That in itself tells us something . .. what? ¾ Earth formed ¾ solid earth must have been molten and differentiated ¾ heavier elements (Fe, Ni) settled to center and lighter ones to top leading to the chemical differentiation we find today. ¾ initial atmosphere must have been stripped away (By ignition of the Sun or perhaps by meteoritic bombardment) ¾ why? see next page. ¾ secondary atmosphere (and ocean) arose from degassing of volatile material from earth’s interior or by cometary bombardment ¾ Initial atmosphere a “weakly reducing” atmosphere ¾ major constituents: N 2 , CO 2 ¾ minor constituents: H 2 , CO ¾ trace amount of O 2 /O 3 from H 2 O + h ν Æ H + OH CO 2 + h ν Æ CO + O O + OH Æ O 2 + H H + H Æ H 2 [And escape of H 2 to space] O + O 2 Æ O 3
Background image of page 2
Evidence that our atmosphere is a secondary atmosphere : Questions: 1. What do we mean by refractory / volatile elements?
Background image of page 3

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
Image of page 4
This is the end of the preview. Sign up to access the rest of the document.

Page1 / 9

Lecture24_Biosphere3 - EAS 1600 Introduction to...

This preview shows document pages 1 - 4. Sign up to view the full document.

View Full Document Right Arrow Icon
Ask a homework question - tutors are online