Survey
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
PROKARYOTES: 2 kingdoms Classification In the 3 Domain system: 2 contain prokaryotes 1. Domain Archaea: Extreme bacteria 2. Domain Bacteria: Everyday bacteria (The third domain is called Eukarya and it includes eukaryotic organisms, including humans!) In the 6 Kingdom system: 2 contain prokaryotes 1. Kingdom Archaebacteria: Extreme bacteria 2. Kingdom Eubacteria: Everyday bacteria (Other kingdoms: Protista, Fungi, Plantae, Animalia) Example of everyday bacteria: Cyanobacteria Previously called blue-green algae Common in water ecosystems Use photosynthesis to generate oxygen Chloroplasts may have evolved from cyanobacteria Examples of Extreme Bacteria Extreme halophiles: Live in high saline environments Seawater evaporating ponds at the edge of San Francisco Bay – used for commercial salt production Examples of Extreme Bacteria Methanogens = Live in swamps and marshes, where other creatures have used all of the O2 Also found in guts of cattle, at garbage dumps and sewage treatment facilities Produce methane as a waste product Examples of Extreme Bacteria Extreme thermophiles: Thrive in very hot environments Orange and yellow colonies of thermophiles in the hot water of a Nevada geyser Common Characteristics Bacteria are the simplest living creatures No nucleus A loop of DNA (not chromosomes) No membrane-bound organelles Most are unicellular Most have a cell wall Are 5 microns in size Now: Draw this bacterium! Figure 6.6 A, B Now create a chart in your notes to compare the characteristics of Bacteria and Archaea. Your column headings should be: Morphology Metabolism Nutrition Habitat Genetics Reproduction Morphology Some bacteria have… Capsule – useful for protection, especially from the human immune system Pili - sticky appendages Flagellum - for motion Classification: Shape A microscope-based method of classifying bacteria 1 m (a) Spherical (cocci) 2 m (b) Rod-shaped (bacilli) (c) Spiral 5 m Metabolism RESPIRATION: when sugar is broken down to make cellular energy (called ATP) some bacteria perform aerobic respiration (using O2), some perform anaerobic respiration (no O2) Obligate aerobes: must have oxygen (E.g. humans!) Obligate anaerobes: live without oxygen (E.g. tetanus bacteria) Facultative anaerobes: use oxygen if present Nutrition Heterotrophic = eat others Autotrophic = make own food Photoautotroph = energy from light Chemoautotroph = energy from chemical reactions, (H2S) many are found near deep ocean vents Genetics Simple ring of DNA Many bacteria have plasmids = extra loops of DNA that often give bacteria additional beneficial genes such as antibiotic resistance Chromosome Asexual Reproduction – Binary Fission Origin of replication 1 DNA copying begins. 2 One copy of the DNA is now at each end of the cell. 3 The plasma membrane pinches inward, and a new cell wall is deposited. 4 Two daughter cells result. Cell wall E. coli cell Two copies of origin Origin Plasma Membrane Bacterial Chromosome Origin Sexual reproduction - Conjugation The direct transfer of DNA between 2 bacteria, via a cytoplasmic bridge (made when 2 pili connect) Hmmm…Why is this considered ‘sexual’? Sex pilus 1 m Crucial roles in ecosystem If prokaryotes were to disappear the prospects for any other life surviving would be dim e.g. Nutrient cycling Function as decomposers, act to recycle chemical elements between the living and nonliving components of the environment (Breaking down corpses, dead vegetation, and waste products) Nitrogen-fixing prokaryotes Symbiotic Relationships 1. Mutualism = both organisms benefit e.g. bacteria in human digestive tract e.g. bioluminescent bacteria on eye of flashlight fish 2. Commensalism = one organism benefits and the other is neither harmed nor helped (rare in nature!) 3. Parasitism = one organism is harmed while the other benefits (usually multi-cellular and nonlethal) Pathogen = similar to parasites, but more often unicellular and lethal Pathogenic Prokaryotes Prokaryotes cause about half of all human diseases (e.g. Lyme disease) Figure 27.16 5 µm Endotoxins Exotoxins When gram negative bacteria die, their membrane breaks down and is toxic A poison produced by the bacteria E.g. Salmonella bacteria that cause food poisoning E.g. Cholera bacteria produce toxins that cause chloride ion release which causes dehydration and severe diarrhea Now: Use your textbook or computer to add in the characteristics of Archaea Watch a movie about the rise of infectious disease!