Reading Science! 6.12CD: Classification of Organisms What’s In A Name? Lexile 870L

6.12CD: Classification of Organisms
Organisms and Environments
Reading Science!
Name: ____________________________________
Date: _________________
What’s In A Name?
Lexile 870L
1 Shakespeare famously wrote in Romeo and Juliet,
“What’s in a name? That which we call a rose by any
other name would smell as sweet.” These words are
meant to say that it doesn’t matter what we call
something. It may not matter to fiction writers
what things are called, but it is very important to
scientists. Scientists need a way to organize and
classify groups of life forms. How scientists do that
has changed over time, as we have learned more
and more about the world around us.
2 As science learns 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,
mushrooms and protists. A domain is the largest rank of organism. There are
three domains: Eukarya, Bacteria, and Archaea.
3 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 protists. Bacteria is the domain composed of
bacteria. These prokaryotes include the oldest fossils on Earth. Though some
bacteria cause disease, others can cure illness. Archaea is the domain
composed of archae. These prokaryotes often reside in extreme places like
the boiling water of a hot spring or the oxygen deprived ocean floor.
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6.12CD: Classification of Organisms
Reading Science!
Organisms and Environments
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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.
5
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.
6
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 to consume other organisms
to get the nutrients we need to survive.
7
Some organisms have only one cell and called unicellular. These organisms
include bacteria, protists, archae, and some fungi. Because they only have
one cell, these organisms are usually tiny. However, some are large enough to
be seen with the naked eye. These organisms must carry out all life processes
within that one cell. In contrast, multicellular organisms have more than one
cell. In multicellular organisms cells serve specialized purposes and depend on
each other to make sure the life processes of the organism succeed.
8
There are two types of reproduction. In asexual reproduction, the offspring
come from a single parent and only carry the genes of that parent. There are
many different ways for an organism to reproduce asexually. They can even
simply divide into two daughter organisms in a process called binary fission.
Many unicellular organisms reproduce asexually. In sexual reproduction, a
new organism is created by the joining of two different sets of genetic
material. This happens with most multicellular organisms.
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6.12CD: Classification of Organisms
Reading Science!
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Organisms and Environments
The final criterion for determining an animal’s Kingdom is looking at how they
can move. Animals which can move by themselves are called motile, while
animals that cannot move by themselves are called sessile.
10 Naming and classifying organisms is a tricky process that must incorporate
new discoveries and information. Knowing the basics can help you think like
a scientist when you read about scientific discoveries.
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6.12CD: Classification of Organisms
Reading Science!
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Organisms and Environments
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Humans are likely to be –
A
eukaryotic and motile
B
prokaryotic and motile
C
eukaryotic and sessile
D
prokaryotic and sessile
A unicellular protist probably –
A
has a complex cell structure
B
has specialized cells
C
has one cell
D
has no cells
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4
Based on the information in this
passage, the reader can reasonably
conclude that –
A
scientists will never change the
classification system again
B
scientists know everything
there is to know about all
organisms
C
scientists have never changed
the classification system
D
new scientific discoveries could
change the current
classification system
In the word photoautotroph, photo
probably means:
A
Picture
B
Light
C
Nutrients
D
Synthesis
6.12CD: Classification of Organisms
Reading Science!
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Organisms and Environments
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Which of the following is the best
summary of the story?
A
B
Eukaryotes and prokaryotes are
different. One has a nucleus
with a cell membrane and the
other does not. Humans are
eukaryotes.
There are many ways to classify
organisms. They can be either
bacteria or archaea.
C
There are three Domains of life.
All living creatures are a part of
the Eukaryotic, Bacteria or
Archaea Domain. There are six
Kingdoms and organisms are
grouped into Kingdoms based
on the complexity of their cell
structure, how the reproduce,
how they obtain nutrients and
how they move.
D
Organisms are everywhere.
Some have a complex cell
structure and some are
unicellular. Some organisms
thrive in extreme places. They
are called archaea and can even
live hot springs and on ocean
floors.
5
Humans are called heterotrophs,
because they –
A
eat other organisms to get the
nutrients they need to survive
B
have a complex cell structure
C
are motile
D
have a nucleus and a cell
membrane