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UGA BIOL 1108 - Plant Evolution

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BIOL 1108 1nd Edition Lecture 11Outline of Last Lecture I. Learning ObjectivesII. MetazoanIII. Ecological rolesIV. CoralV. PhenologyVI. Protists and the origins of multicellularity Outline of Current Lecture I. Learning Objectives II. In The NewsIII. Starch and CelluloseIV. Plant History Current LectureI. Learning Objectives - What are the features that distinguish the green algae from other protists?- What are the features that unite the green algae and the land plants?- What features allowed plants to become established on land? What were the major obstacles?- How did the colonization of land by plants change Earth?II. In The News: Why are Montgomery County, Maryland officials concerned about 29 cases of pertussis in the month of September 2014?- Pertussis, also known as whooping cough, is a highly contagious respiratory disease. It is caused by the bacterium Bordetella pertussis. - Pertussis is known for uncontrollable, violent coughing which often makes it hard to breathe. After fits of many coughs, someone with pertussis often needs to take deep breathes which result in a "whooping" sound. Pertussis These notes represent a detailed interpretation of the professor’s lecture. GradeBuddy is best used as a supplement to your own notes, not as a substitute.most commonly affects infants and young children and can be fatal, especially in babies less than 1 year of age.- The bacterium contains a surface protein, filamentous haemagglutinin adhesin (FHA), which binds to the sulfatides found on cilia of epithelial cells. Once anchored, the bacterium produces tracheal cytotoxin, which stops the cilia from beating. This prevents the cilia from clearing debris from the lungs,so the body responds by sending the host into a coughing fit. These coughs expel some bacteria into the air, which are free to infect other hosts.- In a 1998 paper Dr. Andrew Wakefield claimed that there was a link between the MMR vaccine and children diagnosed with autism.- Diagnosed cases of autism continued to increase in Japan even after the MMR vaccine was withdrawn from use.- Herd Immunity: also called community immunity, describes a form of immunity that occurs when the vaccination of a significant portion of a population (or herd) provides a measure of protection for individuals whohave not developed immunity.o Herd immunity theory proposes that, in contagious diseases that are transmitted from individual to individual, chains of infection are likely to be disrupted when large numbers of a population are immune or less susceptible to the disease. o The greater the proportion of individuals who are resistant, the smaller the probability that a susceptible individual will come into contact with an infectious individual. - In the mid-1990’s the U.S. and many other countries switched from a whole cell pertussis vaccine to one based on component proteins (acellular). The cellular vaccine has fewer side effects but also significantly lower protective value.- Cellular vaccine had 90% immunity and for much longer time, acellular effectiveness is closer to 60%. Side effects included swelling, slight fever, crankiness but virtually no serious effects such as seizures. The more effective cellular form is still widely used in the developing nations of the world. III. Starch and Cellulose- Linear strands of cellulose are made by rosettes of cellulose synthesizing proteins that are free to move in the plasmamembranes of plants and charophyte green algaeo TOP HAT QUESTION: Starch and cellulose are both made of linked glucose molecules. Why is starch so easily digested by animals whereas cellulose is not? Starch is a branched molecule and cellulose is a linear molecule.- Larger number of sugar molecules can join each other to form large polysaccharides such as starch, the storage product of plants and green algae.Starch is a branched α 1-4 linked glucan.- Glycogen is made of linked glucose molecules and is a major storage product of animal cells, often found in high abundance in the liver. - Cellulose is a β 1-4 linked glucan that forms unbranched linear molecules thatheld together by hydrogen bonds.- The cells of plants also have a flexible plasma membrane but secrete a thick cell wall of cellulose that makes the cells rigid and limits their ability to carry out endocytosis and exocytosis. - In addition to the cellulose fibrils there are a number of other biomolecules (pectins, hemicellulose, lignin, etc.) that make up the cell walls of plants.- The tight spacing of the cellulose fibrils plus the associated compounds that fill the small spaces between fibrils creates a cell wall that is relatively inflexible, strong, and waterproof. - Chitin is a long-chain polymer of a N-acetylglucosamine, a derivative of glucose, and it is found in many places throughout the natural world. It is the main component of the cell walls of fungi and the exoskeletons of insects andcrustaceans.IV. Plant History - Plants first colonized the land during the Ordovician period (~475 MYA). o TOP HAT QUESTION: What were the primary obstacles that had to be overcome for algae to successfully colonize the land? Prevent desiccation- Similar modern fungi from the genus Glomus form a simple association with modern liverworts and hornworts, relatives of the only group of land plants around 460 million years ago.- The oldest fossil land plants (~470 MYA) appear to be similar to these liverworts.- As liverworts sucked CO2 out of the atmosphere the amount of greenhouse gas decreased, so the global temperature decreased too. o There is evidence that the relatively sudden drop in the greenhouse gas CO2 led to sudden drop in Earth temperatures, causing massive glaciation of the continents and possibly bringing on the mass extinction event the marked the end Ordovician period at 444 MYA.- Charaphytes are a clade of green algae that are all freshwatero TOP HAT QUESTION: Which Charaphyte green alga is most closely related to the common ancestor of land plants? Coleochaete Based on gene sequence data and the haploid life cycle Coleochaete is actually thought to be more closely related to land plants than either Chara or Nitella.- The flat, disc shaped body plan of Coleochaete allows itto easily attach to a substrate and to resist drying out.- The chloroplasts of all green algae (including land plants) have essentially the same structure and the same complement of photosynthetic pigments.-


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