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Thursday, May 9, 2013
ISN page 138
Bacteria
The Bacterial Cell
• Bacteria are prokaryotes – their genetic
material is not contained within a nucleus.
• Bacteria have a cell wall on the outside and cytoplasm on
the inside. The cells genetic material and ribosomes are
found in the cytoplasm.
• Some bacteria have a flagellum that helps it move. If not,
the cell moves by the air, water, or by other objects.
• Most bacteria are spherical, rod like, or spiral.
• They range in size, most are about 0.5-1
micrometer (one-millionth of a meter)
Obtaining Food & Energy
• Some bacteria are autotrophs – either using
the sun or from chemical substances in their
environment.
• Bacteria that are heterotrophs consume other
organisms or food other organisms make.
• From meat to milk to decaying leaves.
• Many bacteria go through respiration. But some
types of bacteria die in the presence of oxygen!
Reproduction
• When bacteria have plenty of food, the right
temperature, and other suitable conditions,
they thrive and reproduce frequently.
– Some bacteria can reproduce every 20 minutes.
• Some bacteria reproduce by a process called
binary fission.
– One parent creates 2 offspring with identical
genetic material.
• Some bacteria reproduce by two parent cells
combining their genetic material to create a
new offspring.
– The offspring is different form both parent cells.
The Role of Bacteria in Nature
• Oxygen Production
– Scientists believe autotrophic
bacteria were responsible for
adding oxygen to the earth’s
atmosphere billions of years
ago.
• Food Production
– Bacteria helps create yogurt,
cheeses & sour cream. It can
also cause food to spoil.
• Environmental Recycling
– Some bacteria are decomposers in
the soil.
• Environmental Clean Up
– They can help clean up oil spills
and gas leaks.
• Heath & Medicine
– Many of the bacteria in your body
keep you healthy.
• Helps you digest food & makes
vitamins
LEFT PAGE:
Bacteria Questions
Q1: A friend states that all bacteria are harmful
to people. List three reasons why this statement
is not true.
Q2: How might bacteria contribute to a pea
plant growing successfully?