chapters 23 and 24 2013. the most numerous organisms on earth earliest fossils 3.5 billion years old...
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Prokaryotes and Viruses
Chapters 23 and 242013
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Prokaryotes
The most numerous organisms on earthEarliest fossils 3.5 Billion years oldLived before other life evolved.Two major domains: Archaea and Bacteria
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What are the traits of prokaryotes?
1. 2.Living organisms have been categorized into three main groups based on ribosomal RNA analysis.
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Archaea
Different from bacteriaMakeup of cell walls different– no peptidoglycanDifferent lipids in cell membranesDNA has introns
Three groupsMethanogens: convert hydrogen gas and carbon dioxide to methane. Anaerobic, many live in intestinal tract of cows and termites.
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Halophiles: salt lovingThermoacidophiles: acidic environments that are high in temperature.
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Domain Bacteria
Most prokaryotes are bacteriaThree common shapes
BacilliCocciSpirilla
They may occur in chains (streptococci) or clusters (staphylococci)
Work with your shoulder partner to complete the “Classifying Bacteria : Shapes of Bacteria” worksheet.
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Important Bacterial Groups
Proteobacteria: live symbiotically with other organisms Example: nitrogen-fixing RhizobiumGram-Positive Bacteria: many cause disease such as streptocaccus, others are helpful such as Lactobacilli which makes yogurtCyanobacteria: use photosynthesis but lack membrane-bound nucleus and chloroplasts.Spirochetes: move by a corkscrew-like motion. Chlamydia: gram-negative, coccoid pathogens live only inside animal cells.
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Biology of Prokaryotes
Cell Wall: protective, different composition in Bacteria compared to ArchaeaCell Membrane and Cytoplasm: lipid bilayer but different between Archaea and Bacteria
Important metabolic functions occur on the membrane such as respiration.In photosynthetic bacteria, the membrane folds like a thylakoid
DNA: a single closed loop of double-stranded DNA. Additional DNA maybe found in plasmids which are small, circular and self-replicating.
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Capsules and PiliCapsule is made of polysaccharides and protects the cell against drying or harsh chemicals, or in the case of pathogens, the hosts white blood cells.Pili: short, hair-like protein structures on the surface. Help bacteria connect to each other and to surfaces such as the host cell.
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Endospores: a thick-coated, resistant structure formed by some bacteria when environmental conditions aren’t favorable.Can resist high temp., chemicals, radiation, drying and other environmental extremes.This allows the bacteria’s DNA to survive for a long time.
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Nutrition and Metabolism
Prokaryotes obtain nutrients either from nonliving environment or by utilizing the products or bodies of living organisms.Heterotrophs obtain carbon from other organismsAutotrophs obtain their carbon from CO2
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Prokaryotic Habitats
Live in habitats based on their biochemical abilitiesObligate anaerobes: ?Facultative anaerobes:?Obligate aerobes:?Prokaryotes have various temperature requirements for growthMost bacterial species grow best at a pH of 6.5 to 7.5
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Reproduction and Recombination
Prokaryotes usually reproduce by binary fission which is a form of asexual reproduction.
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Prokaryotes can exchange pieces of DNA through recombination
Three ways:Transformation: takes in NDA from its outside environment.Conjugation: two prokaryotes bind together and one transfers DNA to the other.Transduction: a virus obtains a small part of DNA from a host prokaryote which gets copied with the viral DNA
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Bacteria and Humans
How can bacteria cause disease in humans?Exotoxins: toxic substances that bacteria secrete into their environment.
Clostridium tetani = tetanusEndotoxins: not released until the bacteria dies.
E. coli = fever, body aches, diarrhea, hemorrhage and weakness
By destroying body tissues by releasing enzymes.
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Bacteria Microviewers
Complete the activity with both the helpful and harmful bacteria and the microviewers.