Name ______________________________
Date _____________________
Block _______
Classification of Organisms
What’s In A Name?
Shakespeare famously wrote in Romeo and
protists. Bacteria is the domain composed of bacteria.
Juliet, “What’s in a name? That which we call a rose by
These prokaryotes include the oldest fossils on Earth.
any other name would smell as sweet.” These words
Though some bacteria cause disease, others can cure
are meant to say that it doesn’t matter what we call
illness. Archaea is the domain composed of archae.
something. It may not matter to fiction writers what
These prokaryotes often reside in extreme places like
things are called, but it is very important to scientists.
the boiling water of a hot spring or the oxygen
Scientists need a way to organize and classify groups
deprived ocean floor. of life forms. How scientists do that has changed over
time, as we have learned more and more about the
world around us. As science learns and discovers more about
the characteristics of organisms, we have gotten better
at classifying them. The most basic level of
classification is prokaryote and eukaryote. Prokaryotes
are those organisms that don’t have a nucleus or a cell
membrane. They are species of bacteria and archae.
Eukaryotes are those organisms that we can often
readily identify by sight. Each of their cells have a
nucleus and a membrane. They are animals, flowers,
fungi, and protists. A domain is the largest rank of
organism. There are three domains: Eukarya, Bacteria,
and Archaea. Eukarya is the domain composed of
eukaryotes: organisms that have a cell nucleus and a
membrane that encloses a complex structure. Most of
the organisms we commonly think of as “animals” fall
within this domain. It includes all plants, fungi, and
Every living being on the planet falls into one
of these three domains. All eukaryotes are a part of
the Eukarya domain. All bacteria are a part of the
Bacteria domain and all of archaea fall into the
Archaea domain. The next smallest classification group is
Kingdom. The eukaryotic Kingdoms are: Animalia,
Fungi, Plantae, and Protista. The prokaryotic
Kingdoms are Eubacteria and Archaea. Organisms
are classified at this level based on the complexity of
their cell make up, and how they obtain nutrients,
reproduce, and move. There are two ways an organism can get
nutrients. Autotrophs make their own, while heterotrophs
consume other organisms to get what they need to
survive. Most bacteria and archae are autotrophs.
Many plants are photoautotrophic. They use light from
the sun to manufacture the food they need to survive.
People are heterotrophs. We can walk around all day
with our arms outstretched to the sun and still need
asexually. They can even simply divide into two
to consume other organisms to get the nutrients we
daughter organisms in a process called binary fission.
need to survive. Many unicellular organisms reproduce asexually. In
Some organisms have only one cell and called
unicellular. These organisms include bacteria, protists,
archae, and some fungi. Because they only have one
sexual reproduction, a new organism is created by the
joining of two different sets of genetic material. This
happens with most multicellular organisms. cell, these organisms are usually tiny. However, some
The final criterion for determining an animal’s
are large enough to be seen with the naked eye. These
Kingdom is looking at how they can move. Animals
organisms must carry out all life processes within that
which can move by themselves are called motile, while
one cell. In contrast, multicellular organisms have more
animals that cannot move by themselves are called
than one cell. In multicellular organisms cells serve
sessile. specialized purposes and depend on each other to make
sure the life processes of the organism succeed. There are two types of reproduction. In
Naming and classifying organisms is a tricky
process that must incorporate new discoveries and
information. Knowing the basics can help you think
asexual reproduction, the offspring come from a single
like a scientist when you read about scientific
parent and only carry the genes of that parent. There
discoveries. are many different ways for an organism to reproduce
Directions: Answer the following questions in complete
sentences.
1. What are the 3 Domains?
Directions: Answer the following questions in complete
sentences.
1. What are the 3 Domains?
2. What are the 6 Kingdoms and which Domain to
they fall into?
2. What are the 6 Kingdoms and which Domain to
they fall into?
3. Define Autotroph
3. Define Autotroph
4. Define Heterotroph
4. Define Heterotroph
5. Define Unicellular
5. Define Unicellular
6. Define Multcellular
6. Define Multcellular
7. Define asexual reproduction
7. Define asexual reproduction
8. Define sexual reproduction
8. Define sexual reproduction