7th Grade Biology
Obtaining Food
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Bacteria must have a source of food and a
way of breaking down the food to release
energy.
Some bacteria are autotrophs and make
their own food.
They make food in one of two ways.
Some capture the sun’s energy like plants.
Others use the energy from chemical
substances in their environment.
Obtaining food
Some bacteria are heterotrophs and
cannot make their own food.
 They must consume other organisms or
the food that other organisms make.
 Heterotrophic bacteria may consume a
variety of foods- from milk and meat, to
decaying leaves on a forest floor.
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Respiration
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Like all organisms, bacteria need a
constant supply of energy to carry out their
functions.
This energy comes from food.
The process of breaking down food to
release energy is called respiration.
Like many other organisms, most bacteria
need oxygen to break down their food.
Some bacteria do not need oxygen, in fact,
for them oxygen is a poison.
Reproduction
When bacteria have plenty of food, the
right temperature, and other suitable
conditions, they thrive and reproduce
frequently.
 Some can reproduce every 20 min.
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Brain Check
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What is an autotroph?
Makes it own foodsimilar to a plant.
What is a heterotroph?
Must consume other
organisms
The process of
breaking down food to
release energy is
called __________.
respiration
Asexual Reproduction
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Bacteria reproduce by a process called binary
fission, in which one cell divides to form two
identical cells.
Binary fission is a form of asexual reproduction.
Asexual reproduction is a process that involves
only one parent and produces offspring that are
identical to the parent.
During this process, a cell duplicates its genetic
material and then divides into two separate cells.
Each new cell gets its own complete copy of the
parent cell’s genetic material as well as some of the
parent’s ribosomes and cytoplasm.
Sexual Reproduction
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Sexual reproduction involves two parents who
combine their genetic material to produce a new
organism, which differs from both parents.
During a process called conjugation, one bacterium
transfers some of its genetic material into another.
Using a thin, threadlike bridge that joins the two
cells.
When these bacterium divide by binary fission, the
new genetic material passes to a the new cells.
Conjugation does not increase the number of
bacteria.
It does result in new bacteria that are genetically
different from the parent cells.
Endospore Formation
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Sometimes, conditions in the environment become
unfavorable for the growth of bacteria.
Some bacteria can survive harsh conditions by forming
endospores.
An endospore is a small, rounded, thick-walled, resting
cell that forms inside a bacterial cell.
It contains the cell’s genetic material and some of its
cytoplasm.
Because endospores can resist freezing, heating, and
drying, they can survive for many years.
The bacteria that causes botulism, produce heat resistant
endospores that can survive improperly canned food.
They are very light, and can be carried off by a breeze,
moving it to a better place to open up and multiply.
Words
Pasteurization-the food is heated to a
temperature high enough to kill most
harmful bacteria without changing the
taste of the food.
 Louis Pasteur, is its inventor.
 Decomposers- organisms that break
down large chemicals in dead
organisms into small chemicals.
 They are nature’s recyclers.
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