Download Name Notes Page ______ 1 Bacteria Objectives

Name ________________
Notes Page ______
Bacteria
Objectives
• Give reasons that bacteria are the simplest living things.
• Describe ways in which bacteria cells are different from all other
organisms’ cells.
• Compare and contrast sexual and asexual reproduction.
• Provide examples of how bacteria are helpful to organisms.
The BIG Idea
• Bacteria and protists have the characteristics of living things.
Key Concept
• Bacteria are single-celled organisms without nuclei.
Bacteria
are
the
smallest
living
things
and
live
in
many
environments
•
The names of the organisms belonging in the kingdoms (and domains)
Archaea and Bacteria are probably unfamiliar to you. Yet, you
encounter them every single day.
•
Bacteria are everywhere: on your skin, in the ground, in puddles and
ponds, in the soil, and in the sea. About 300 species of bacteria are
living in your mouth right now. Need Orbitz?
•
Bacteria are the simplest kind of life on Earth. All bacteria are
composed of just one cell without a nucleus. This means they are
prokaryotic. Their genetic material is contained in loops within the cell.
Bacteria are different in structure to other cells
•
Bacterial cells are different from the cells of other organisms. A bacterial
cell is about one-tenth to one-twentieth the size of a typical cell from
organisms such as animals, plants, fungi, or protists.
•
Despite their small size, bacteria are simple only when compared with
more complex cells. Bacteria are much more complex than viruses,
because they have many internal structures that viruses do not have.
(Remember, a virus is not a living thing!)
1
•
An example of such a structure is the cell wall. Bacterial cells also
contain many large molecules and structures that are not found in
viruses.
•
In addition to having a cell wall, bacterial cells have structures like
animal cells. For example, they have ribosomes, which produce
protein. It also contains cytoplasm.
•
Another structure that some bacteria have is called the flagellum. This
is a long, whip-like structure that allows the cell to move.
•
Some bacteria also have chlorophyll so that they can obtain their own
energy. If an organism obtains its own energy, we say it is an
autotroph. Other bacterial cells, which must “eat” to survive are called
heterotrophs. This is true for all organisms in all kingdoms.
What type of cell are bacteria? Prokaryotic
How does the bacterial cell compare in size with other cells? It is
much smaller.
Why are bacteria considered the simplest of all organisms?
Bacteria are unicellular prokaryotes, which mean they
lack a nucleus. They have very few cell structures.
Bacteria are classified into one of two domains and kingdoms.
•
Unlike animal cells, which do not have a well-defined shape, bacteria
have three basic shapes.
o Round-shaped bacteria may occur singly or in pairs, chains, or
clusters.
o Sprial-shaped bacteria occur in single strands.
o Rod-shaped bacteria may occur singly or in chains.
•
The shape of the bacteria helps scientists identify the type of bacteria.
2
•
Scientists will classify the bacteria into one of two domains. Each of
these domains only has one kingdom. The kingdom has the same name
as the domain.
•
Bacteria is one classification of bacteria. They are the most common
and are found in nearly every environment.
•
Archaea are similar in size
to bacteria, but share more
characteristics with the cells
of complex organisms like
plants and animals.
Archaea and bacteria are found in many environments.
•
Archaea are single-celled organisms that can survive in the largest range
of environments. These environments may be very hot, very cold, or be
poisonous to other organisms. As a result, scientists often classify the
group archaea on where they live. There are several different kinds of
archaea.
o Methanogens take their name from methane, the natural gas
they produce. These Archaea die if they are exposed to oxygen.
They may live in the dense mud of swamps and marshes, and in
the guts of animals such as cows and termites.
o Halophiles live in very salty lakes and ponds. Some halophiles
die if their water is not salty enough. When a salty pond dries
up, so do the halophiles. They can survive drying and begin
dividing again when water returns to the pond.
o Thermophiles are archaea that thrive in extreme heat or cold.
They may live in hot environments such as hot springs, near hot
vents deep under the sea, or buried many meters deep in ice.
3
What are the three bacteria shapes? Spiral, rod, and round.
How can scientists classify all bacteria? By their shape.
How can scientists classify just archaea? By where they live.
Where do Halophiles live? In very salty lakes and ponds.
Where do thermophiles live? In extremem heat or cold.
•
Most single-celled organisms without a nucleus are classified as
bacteria. Bacteria are found in almost every environment and perform
a variety of tasks. Some bacteria contain chlorophyll. Using sunlight for
energy, these bacteria are an important food source in oceans. These
bacteria also release oxygen gas, which animals need to breathe.
•
Bacteria without chlorophyll perform different tasks. Some bacteria
break down parts of dead plants and animals to help recycle matter.
Some bacteria release chemicals into the environment, providing a
food source for other organisms.
•
Scientists often group bacteria by the roles they play in the
environment. Three of the most common roles are listed below.
•
Bacteria that transform energy from sunlight into energy that can be
used by cells are called producers. These bacteria are a food source
for organisms that cannot make their own food.
•
Decomposers get energy by breaking down materials in dead or
decaying organisms. Decomposers help other organisms reuse materials
found in decaying matter.
•
Some bacteria live in very close relationship either inside or on the
surface of other organisms. Some of these bacteria have no effect on
their host organisms or host cells. Some bacteria help their hosts. Other
bacteria are parasites, harming their host.
4
How do scientists classify bacteria (non-archaea)? They classify
them by the role they play.
How do produces get energy? By converting sunlight
Where do bacterial parasites live? Insider or on other
organisms.
Why are bacteria (non-archaea) not classified by where they live?
Bacteria are found everywhere and many would share
the same location. Therefore, they are classified by the
role they have.
What are some common traits of bacteria and archaea?
They are both single-celled and they do not have a
nuclei.
Bacteria reproduce both sexually and asexually.
•
Living things reproduce, forming other organisms like themselves. Recall
that this is one of the characteristics of life.
•
Every organism contains genetic material, which is a code contained in
DNA. In order to reproduce, an organism must have a copy of this
material, which is passed on to its offspring.
•
There are two types of reproduction: sexual and asexual. Sexual
reproduction requires two parents whereas asexual reproduction
requires only one parent to produce offspring.
•
Most bacteria reproduce by an asexual process called binary fission.
•
In this process, material from one cell separates into two cells. The
genetic material of the original cell first doubles so that each daughter
cell (the new cell formed) has an exact copy of the DNA of the original
cell. Each cell formed is genetically identical to the parent cell. If this
were how humans reproduced, you would look exactly like your parent.
5
•
Asexual reproduction allows for rapid growth. Division can occur as
quickly as every 20 minutes. Imagine our school population doubling in
size every 20 minutes. However, if every bacterium has the same
genetic information, it will be easier to kill. Think about the movie
Independence Day. By infecting one, you can infect them all…so to say.
•
Some bacteria reproduce through sexual reproduction. For bacteria to
reproduce sexually, it needs to find another cell to reproduce with.
•
Sexual reproduction involves two parents who combine their genetic
material to produce a new organism.
•
Bacteria undergo a special form of sexual reproduction called
conjugation. In this process, two bacteria cells exchange genetic
information. They do this so their offspring will have different genetic
information. Why? This increases the offspring’s chance of survival.
Differences will allow the organism to fight off things that may kill it, such
as antibiotics.
•
Conjugation does not produce new cells! After conjugation, the
cell will undergo binary fission and produce two cells with genetic
information different than what the parent cell originally had.
•
Sometimes, the conditions bacteria live in are unfavorable for growth
and reproduction. In this case, the bacteria can form an endospore.
These are small, round, thick-walled capsules that form inside the
bacteria cell. It includes the genetic information needed for the bacteria
to survive. Think of it as a shelter of a bacterial cell. It has everything it
needs to survive and the shelter protects it from the environment.
What molecule contains the cell’s genetic information? DNA
What process do single-celled organisms use to divide?
Binary fission
What can a bacteria cell form should conditions for survival
become unfavorable? An endospore
6
Why do bacteria cells benefit from sharing genetic information
through conjugation? When the cells share information, it
may contain instructions on how to defend against
certain infections or antibiotics. This will increase the
chance of survival for that bacteria.
Bacteria may help or harm other organisms.
•
Some bacteria, such as producers and decomposers, are helpful to
other organisms. But other bacteria can be harmful. These bacteria can
cause diseases in animals and plants. However, it is important to
remember that less than one percent of bacteria harm humans. Most
bacteria are helpful or harmless to humans.
•
If you were to take a shovelful of soil, it would contain trillions of
bacteria. Every leaf and dead animal on the ground is covered in
bacteria. These bacteria break down the remains so they are available
to other organisms to use.
•
Bacteria are used to break down sewage and are able to clean water.
Bacteria can even convert substances into new substances other
organisms can use. For example, some bacteria can convert nitrogen
gas into nitrogen compounds. This process, called nitrogen fixation,
makes nitrogen available to plants in a form that is useful to them.
•
Our book does a great job of explain several roles of bacteria in our
everyday lives. This chart summarizes them.
C ATEGORY
Fuel
E XAMPLE …
•
Bacteria produce methane, which is a major
component in natural gas.
Food
•
Bacteria help produce some types of food such as
yogurt and cheese.
7
Environmental
•
Recycling
Plants break down natural substances like leaves
and dead animals into nutrient-rich soil.
Environmental
•
Cleanup
Scientists use bacteria to clean up oil spills in the
ocean.
Health and
•
Some bacteria help digest food.
Medicine
•
Other bacteria provide vitamins for our body.
•
They even fight for their space in our body so that
harmful bacteria cannot be there.
•
Unfortunately, there are some bacteria that harm humans and other
organisms. These bacteria are harmful in one of three ways:
o The can invade parts of the body, multiply in body tissues and
dissolving cells.
o They can poison the body with chemicals they produce and
release.
o They can poison the body with chemicals that are part of the
bacteria themselves.
•
Two ways to fight bacterial disease include vaccinations and
antibiotics. However, the abuse, misuse, and overuse of antibiotics has
caused harmful bacteria to become resistant to the antibiotics.
•
Vaccines work by injecting an organism with a weakened version of the
bacteria. This allows your body to learn how to fight it.
What percent of bacteria is helpful or harmless to humans? 99%
List several examples of how bacteria are helpful to our everyday
lives. ________________________________________________
_____________________________________________________
_____________________________________________________
_____________________________________________________
8