Lecture19 - EAS 1600 Introduction to Environmental Sciences...

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EAS 1600 Introduction to Environmental Sciences ____________________________ Class 19 - The Biosphere: Part 2 Origins and Evolution of Biosphere within the 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. THE TREE OF LIFE By examining the genome of cells, biologists have established that there are two basic forms to all life: ¾ procaryotes ¾ bacteria (sometimes referred to as eubacteria) ¾ archaea (sometimes referred to as archybacteria) ¾ eukaryotes (this includes homo sapiens) Good source for info on tree of life: http://phylogeny.arizona.edu/tree/phylogeny.html Procaryotes are: ¾ smallest, least complex cellular organisms ¾ typical bacteria ~ 1 micrometer ¾ typical eukaryotic cell ~ 10 - 100 micrometers ¾ distinguished from eukaryotes by their lack ¾ of a nuclear membrane ¾ any internal organelles Schematic of procaryotic cell http://fig.cox.miami.edu/~cmallery/150/proceuc/colipic.htm Schematic of eukaryotic cell http://www.ucmp.berkeley.edu/alllife/eukaryotamm.html Procaryotes are: ¾ Central to biosphere on individual and global level because ¾ of the diversity of their metabolic processes ¾ they comprise about 90% of biosphere ¾ the ability of archaea to live in extreme environments ¾ symbiotic relationships with many eukaryotes ¾ their role in evolution (more on this in a later lecture) ¾ come in three basic shapes Size and fundamental shapes of procaryotes revealed by three genera of Bacteria (l to r): Staphylococcus (spheres), Lactobacillus (rods), and Aquaspirillum (spirals). http://textbookofbacteriology.net/bacteriology.html
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Metabolic Processes: Two Basic Kinds ¾ Autotrophic ¾ synthesis of living protoplasm from inorganic matter in the environment ¾ This requires non-catabolic energy input ¾ Two Types ¾ lithotrophic or chemoautotrophic ¾ photoautotrophic ¾ Heterotrophic ¾ synthesis of living protoplasm from organic matter in the environment (i.e., us) ¾ This usually involves catabolism Note: Autotrophs have an autotrophic metabolism (use inorganic C) Heterotrophs have a heterotrophic metabolism (use organic C) Remember: Catabolism refers to the breakdown of organic material to release energy! LITHOTROPHS (or chemoautorophs) ¾ Use inorganic compounds as their energy source ¾ can be facultative or obligate lithotrophs ¾ facultative lithotrophs can use heterotrophy when organic material is present. ¾ (Why would an organism that can be lithotrophic want to use heterotrophy? We will find out later in this lecture) Examples: ¾ Methane bacteria: CO 2 + 4H 2 Æ CH 4 + 2H 2 O – (using unique enzymes) ¾ These are actually archaea (or archybacteria). ¾ They are obligate anaerobes ¾ So they can only exist in the absence of O 2 .
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Lecture19 - EAS 1600 Introduction to Environmental Sciences...

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