You Never Know!
The Classification of Life How would you do it and why? What can we learn from this exercise about the evolutionary relationships among organisms on earth?
Classification Possibilities and Potential Strategies Based Upon: Cell Structure and Complexity Genetic Composition Basic Metabolism Strategies and Mode of Life Size Biotic History and Fossil Antiquity Evolutionary Relationships
Darwin's Theory of Natural Selection. Fact #1 - Without constraints, populations will grow exponentially, producing an ever more rapidly growing number of organisms. Fact #2 - In spite of this prediction, the numbers of individuals in a population remains near equilibrium, fluctuating above and below some mean value. Why? Fact #3 - Resources are limited. From these three facts, Malthus concluded that there was a struggle for existence.
Darwin s Theory (Cont.): Darwin combined this with two addition facts: Fact #4 - Sexually reproducing individuals are unique. There is individual variation across a population. Fact #5 - Much (but not all) of the individual variation is heritable. This observation came from animal breeders. (Some of observed variation is environmental, some is genetic.) These facts led Darwin to the conclude that some individuals are better equipped to survive and reproduce than others. This process came to be known as Natural Selection. Through many generations of time, evolution is the result. (Darwin used "descent with modification.")
The Five Kingdom System?
A New Look at Life on Earth
Typical Prokaryote Organism But Atypical in Ecologic Roles
Lithotrophs. Lithotrophy, a type of metabolism that requires inorganic compounds as sources of energy, is established in both the Archaea and the Bacteria. The methanogens utilize H2 as an energy source, and many extreme thermophiles use H2S or elemental sulfur as a source ofenergy for growth. Lithotrophic Bacteria utilize inorganic substrates including H2, NH3, NO2, H2S, S, Fe++, and CO. Ecologically, the most important lithotrophic Bacteria are the nitrifying bacteria, Nitrosomonas and Nitrobacter that together convert NH3 to NO2, and NO2 to NO3, and the colorless sulfur bacteria such as Thiobacillus that oxidizes H2S to S and S to SO4. Most lithotrophic bacteria are autotrophs, and, in some cases, they may play an important role in primary production of organic material in nature. Lithotrophic metabolism does not extend to eukaryotes (unless a nucleated cell harbors lithotrophic endosymbiotic bacteria), and these bacteria are important in the biogeochemical cycles of the elements.
Origins of Life?? Deep Sea Vent Communities
Why the Deep Sea??
Tectonic Picture
It s a Rockin Place
Importance of Archaeans Methanogens-facultative anaerobes reduce CO2 to CH4 Extreme Halophiles Thermoacidophiles More closely related to eukaryotes than bacteria! Life on other worlds? Mars? Europa?
Tube Worms--Life without a Stomach!
Life on Other Planets?
Origins of Eukaryotes-The Environmental Setting Atmospheric Oxygen increases from near zero to toxic levels about 2 billion years ago Ozone Layer begins to form Selection for organisms that could cope with oxygen
Mitochondria Do There Magic!
Significance of Eukaryote Evolution Most significant single advance of organic evolution Division of labor within the cell Multicellular organisms evolved Basic Organization of eukaryotic cells evolved once Organelles striking similar to each other Mitochondria Plastids of autotrophs Flagella Biochemical similarities of all eukaryotes Glucose metabolism Krebs cycle Protein synthesizing machinery
Possible Symbiotic Origins of Eukaryotes
The Five Kingdom System? I Think Not!!