Biology II
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Transcript of Biology II
Biology II
Bacteria
• The invention of the microscope opened our eyes to the hidden, living world around us.
• Microscopic life covers nearly every square centimeter of earth
Prokaryotes
• The smallest and most common microorganisms
• Unicellular organisms that lack a nucleus and a membrane bound organelles
• Mainly Bacteria
• Prokaryotes can be divided into two very different groups– Eubacteria– Archaebacteria
Eubacteria
• Include a wide range of organisms with different lifestyles
• Eubacteria live almost everywhere• Largest Prokaryote Domain• Cell membrane around cytoplasm• Some have an extra cell wall on the outside to
resist damage
Archaebacteria
• Lack the same carbohydrates of eubacteria and also have different membrane lipids
• Also, the DNA sequences of key archaebacterial genes are more like those of eukaryotes than those of eubacteria
• Many archaebacteria live in extremely harsh environments
Identifying Prokaryotes
• Prokaryotes are identified by characteristics such as: – shape– the chemical nature of their cell walls– the way they move– the way they obtain energy
Shapes
• Bacilli – Rod shaped• Cocci – Spherical Shaped• Spirilla – spiral and corkscrew shaped
Cell Walls
• Eubacteria – Have peptidoglycan• Archaebacteria – Don’t have peptidoglycan
Movement
• Flagella• Lash, snake or spiral forward• They do not move at all
Metabolic Diversity
• No characteristic of prokaryotes illustrates their diversity better than the way they obtain energy
Heterotrophs
• Must take inorganic molecules for both energy and a supply of carbon– Chemoheterotrophs: must take in organic
molecules for energy– Photo heterotrophs: Use sunlight for energy but
need organic compounds for a carbon source
Autotrophs
• Chemoautotrophs: perform chemosynthesis to make carbon from carbon dioxide. Does not require sunlight
• Photoautotrophs: Use light to convert carbon dioxide and water into carbon compounds and oxygen gas
Getting Energy
• Bacteria need a constant supply of energy– Obligate aerobes- Require costant supply of
oxygen– Obligate anaerobes- Need no oxygen, for some
oxygen will kill it– Facultative anaerobes- Survive with or without
oxygen
Releasing Energy
• Like all organisms, bacteria need a constant supply of energy
• This energy is released by the process of cellular respiration or fermentation or both
Growth and Reproduction
• Bacteria can grow really fast• Types of Reproduction– Binary fission– Conjugation– Spore formation
Binary Fission
• When a bacterium has grown so that it has nearly doubled in size, it replicated its DNA and divided in half producing 2 identical daughter cells
Conjugation
• Many bacteria are also able to exchange genetic information by a process called conjugation
• This transfer of genetic information increases genetic diversity
Spore Formation
• When growth conditions become unfavorable, many bacteria form structures called spores
Endospore
• A type of spore formed when a bacterium produces a thick internal wall that encloses a thick internal wall that encloses its DNA and a portion of its cytoplasm
Importance of Bacteria
• Decomposers– Break down dead matter
• Nitrogen Fixers– Converts nitrogen into a form plants use
Decomposers
• As decomposers, bacteria help the ecosystem recycle nutrients, therefore maintaining equilibrium in the environment.
Human Uses of Bacteria
• Used in food and beverage production• Industries: petroleum, water, mining, drugs• Inside of us (symbiosis)– E. Coli
• Drug Research
Helpful Bacteria
• Bacteria help the body digest food and produce certain vitamins
• Some bacteria fight off diseases• Helps break down all the dead plant and
animal remains making nutrients for the soil