Bio171-F10-Lec 34 - Biology 171 Monday December 6, 2010...

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Unformatted text preview: Biology 171 Monday December 6, 2010 Lecture 34 : Evolution of Human s Announcements Discussion This Week: Selection on Human Populations Exam 4: Monday, Dec. 20, 7-9 PM. Covers lectures 28 (viruses) 37 & discussions 9-11 (phylogeny reconstruction, Ant-fungal coevolution, Selection on human populations Text Reading Lecture 34 : 4th: Chapter 34 (668-673) 3rd: Chapter 34 (762-767) Lecture 35 : 4th: Chapter 55 (1110-1123) 3rd: Chapter 55 (12491260) Fungi (concluded) Primates & Hominids Low Human Genetic Diversity - Why? Australopithicus, Paranthtopus & Homo Neanderthals & Us Our Recent African Origins 1 The Ecology & Evolutionary Biology of Fungi Fungi play important ecological roles in the environment They also have important evolutionary interactions with other organisms Fungi are master decomposers, marvelous mutualists, and miserable agents of disease 15 Fungi Are Critical to Decomposition and Nutrient Cycling Many fungi can digest cellulose and lignin (the structural components of w 16 Note The Importance of Decay of Residues for the Carbon Cycle Plant residues contain recalcitrant compounds that are difficult to break down e.g. cellulose & lignin. In terrestrial and freshwater ecosystems, fungi are primary decomposers of plant residues 17 Decomposition of detritus limits the rate at which nutrients move through an ecosystem. Decomposition rate is influenced by abiotic conditions and the quality of the detritus as a nutrient source. 18 The Master Decomposers To facilitate decomposition of dead organic matter, fungi release enzymes to break down organic tissue Digestion takes place outside their cells and the digestion products are then absorbed by hyphae Peptidases break bonds between amino acids and carbon compounds in dead tissue, releasing nitrogen Chitinases, lignases and cellulases are released by some fungi to break down complex carbohydrates into sugars that can be used for energy Eventually, the carbon may be respired back into the atmosphere as CO 2 19 The Masters of Decomposition During the Permian mass extinction, there is a huge pulse in fungal spore fossils The fungi were probably very abundant because of all the dead organisms available for decomposition ! 20 Much of the biomass of forest ecosystems is underground and approximately half of that is composed of fungal tissue 21 Its mycelia cover 38 acres in Crystal Falls, MI, living underneath an Iron County forest near the Wisconsin border. It is believed to be 1,500 to 10,000 years old and weighs about 100 tons. The species is called Armillaria gallica, and the mushrooms it produces are commonly called "honey mushrooms." The mushroom (reproductive structure) is edible but should be cooked and eaten only in moderation....
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Bio171-F10-Lec 34 - Biology 171 Monday December 6, 2010...

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