bio 120 bacteria lab

bio 120 bacteria lab - A Introduction Life on earth is...

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A. Introduction Life on earth is divided into three domains: Bacteria, Archaea and Eukarya. It is believed that Eukaryotes arose from Prokaryotes about 1.5 billion years ago. Prokaryotes are unicellular and microscopic, and their cells lack a membrane enclosed nucleus and organelles. Their DNA is in a nucleoid and they rapidly reproduce and mutate. All prokaryotes are apart of either the domain Bacteria or the domain Archaea. Among the domain bacteria, the most diverse and widespread prokaryotes, cyanobacteria and eubacteria are some of the main groups (Campbell 13-14). Cyanobacteria are photoautotrophs, and they are the only ones with plantlike, oxygen-generating photosynthesis. They can exist under harsh conditions because they can obtain energy, carbon, and nitrogen from the air, which makes them the “most nutritionally independent organisms on earth.” Most can carry out photosynthesis and nitrogen fixation. When they are in a favorable environment, they multiply and form a mat on the surface of water that decreases oxygen in the water, and can make it unfit to drink. Cyanobacteria had major contributions to life as we know it today. During the Archaean and Proterozoic eras, cyanobacteria generated oxygen in the atmosphere that made it suitable for future organisms. Also, by endosymbiosis, they lived in eukaryotic cells within plants and made food for them, which is the origin of the eukaryotic mitochondrion(Lum 48). Eubacteria is responsible for many human diseases, but also helps maintain health and form vital parts of all of Earth’s ecosystems. They are so tiny that it is difficult to see with a microscope, so they are identified by their cell wall, positive or negative stain, or their shape. The wall is made of cross-linked chains of peptidoglycan, a polymer that combines amino acid and sugar chains. There are many different shapes of bacterium such as coccus, bacillus, spirillym, or vibrio. “Natural flora” is a bacterium that can be helpful by creating unfavorable growth for pathogens. Bacteria can be in the air, in a persons mouth, or in the water(bioluminescent bacteria). When there is plenty of food, bacteria rapidly divides, but during poor conditions, they form endospores that can harm humans. These endospores allow the bacteria to be in a dormant state and survive during harsh conditions. Some Eubacteria are used at wastewater treatment plants to help clean the water. Others are used to make grapes into wine and milk into cheese (Madigan 1). B. Materials and Methods 1)For the Cyanobacteria experiment, we observed Anabaena and its heterocysts under the 100x microscope, using the oil immersion technique. This technique reduced the scattering of light so that we could see the organism clearer. 2)Bacterial Structure- we observed the different structures of bacterium under the
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This note was uploaded on 09/29/2008 for the course BISC 120 taught by Professor Webb,wetzer,? during the Fall '07 term at USC.

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bio 120 bacteria lab - A Introduction Life on earth is...

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