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Download Chapter 17: The History and Diversity of Life
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Chapter 17: The History and Diversity of Life Section 17-3: Bacteria – The First Organisms Ancient Prokaryotes Scientists have found simple, prokaryotic microfossils from about 3.5 bya The first prokaryotes did not need oxygen, then over time some organisms developed the ability to do photosynthesis Ancient Prokaryotes Photosynthetic prokaryotes began producing large amounts of oxygen by 2.2 – 2 bya As oxygen accumulated in the atmosphere, some early life forms went extinct while others were forced into deep, airless hiding places Ancient Prokaryotes Some evolved the ability to USE oxygen to make energy by cellular respiration Living Prokaryotes Only organisms for about half of Earth’s history Modern prokaryotes so diverse because they have had the longest time to evolve Bacteria are everywhere – from the coldest mountains, to the bottom of the ocean floor, and even in volcanic hot springs Living Prokaryotes Very adaptable because they are small and simple Many are necessary for human survival What are Bacteria? They are prokaryotes that have a cell membrane surrounded by a cell wall, whose genetic material is contained in a single circular strand of DNA No nucleus, no organelles Bacterial Kingdoms Kingdom Eubacteria Called “true” bacteria because they have a thick, rigid cell wall made of the carbohydrate peptidoglycan Very diverse, some photosynthetic Kingdom Archaebacteria “Ancient” bacteria that live in extreme conditions (intense temperatures, very salty water, no oxygen) Cell walls made of lipids Bacterial Reproduction Asexual reproduction by binary fission Chromosome duplicates and one cell divides into two cells Even simpler than mitosis Bacterial Reproduction Some bacteria, like E. coli, sometimes undergo conjugation Simple form of sexual reproduction that allows for genetic material to be exchanged between two bacteria Some can also go through transformation, where bacteria pick up DNA pieces from other bacteria
