1. Classification is the arrangement of organisms
into orderly groups based on their similarities.
Classifying living things makes it easier for
biologists to find answers to many important
questions.
2. In order to classify an organism, a biologist
must use a system that groups organisms
according to shared characteristics and their
relationships between one another.
3. There are 7 taxonomic levels of classification
used by biologists – kingdom, phylum, class,
order, family, genus, and species.
4. A kingdom is the largest, most general
taxonomic category. There are 6 identified
kingdoms to this point – Archaebacteria,
Eubacteria, Protista, Fungi, Plantae, and
Animalia.
5. A genus is a group of similar species. A species
is the smallest and most specific taxonomic
category. Organisms that belong to the same
species can mate and produce fertile offspring.
6. Aristotle developed the first classification
system over 2,000 years ago. His system only
had two kingdoms – Plant and Animal.
7. The animal kingdom was divided into smaller
groups based on where animals lived. The plant
kingdom was divided into smaller groups based
on size and structure. This worked fine until
other organisms like protists and bacteria were
discovered.
8. Carolus Linnaeus was a Swedish physician and
botanist who lived in the 1700’s. He founded
taxonomy, which is the science of identifying,
classifying, and naming living things.
9. Organisms are classified based on
characteristics which may include the type of
cells, number of cells, method of movement,
method of obtaining food and chemical makeup.
10. Modern scientists also study fossils, hereditary
information, and early stages of development to
classify organisms. All of this information is
used to determine an organism’s phylogeny, or
evolutionary history.
11. By classifying organisms, scientists are able to
give them scientific names. A scientific name is
always the same for a specific organism no
matter how many common names it might have.
12. The scientific name is made up of 2 words – the
genus and the species of an organism. This
special two-word naming system developed by
Linnaeus is called binomial nomenclature.
13. Scientific names are either Latin or Greek. The
first word (genus) always begins with a capital
letter, and the second word (species) always
begins with a lower case letter. Both words are
either underlined or italicized.
14. Scientific names help scientists to avoid
confusion when discussing organisms. Most
organisms have a common name in every
language! Scientific names let scientists know
they are talking about the same organism.
15. Scientific names are also important because they
give descriptive information about the species
and allow information about organisms to be
organized and found easily and efficiently.
16. Taxonomists have developed special guides
known as dichotomous keys to help identify
unknown organisms. A dichotomous key
consists of several pairs of descriptive
statements that have only 2 alternatives
responses.
17. Bacteria have been divided into two kingdoms.
They are different from all other living things in
that they are prokaryotes, organisms that do not
have a nucleus. They are also known by the
name Monerans.
18. Archaebacteria are a type of bacteria that are
able to live where most organisms can’t survive.
The prefix archae comes from a Greek word
meaning “ancient.” Archaebacteria can be
found in hot springs and deep sea thermal vents.
19. Eubacteria make up the rest of the bacteria.
These bacteria are found in soil, water, and even
on and in the human body.
20. Escherichia coli (E. coli) is found in human
intestines, where it produces vitamin K.
Another kind of bacterium converts milk to
yogurt, and other species cause ear and sinus
infections.
21. Protists, members of kingdom Protista, are
single-celled or simple multicellular organisms.
Protists can range in size from microscopic to
giant seaweed (kelp).
22. Protists include protozoa (animal-like protists);
algae (plant-like protists); and slime and water
molds (fungus-like protists).
23. Fungi were originally classified as plants, but
they do not obtain nutrients by photosynthesis.
Because of their unusual combination of
characteristics, they were placed in a separate
kingdom.
24. Fungi are saprophytes because they absorb
nutrients from their surroundings after breaking
them down with digestive juices.
25. Plants can vary in size and form. They are
complex, multicellular organisms that are
usually green and use the sun’s energy to make
sugar by a process called photosynthesis.
26. Animals are complex, multicellular organisms.
Most of them can move from place to place and
have nervous systems that help them sense and
react to their surroundings. Animal cells differ
from those of fungi, plants, most protists, and
bacteria because animal cells do not have cell
walls.
27. Autotrophs are organisms that make their own
food. Another name for an autotroph is a
producer. Heterotrophs are organisms that
must obtain their nutrients from other
organisms. Another name for a heterotroph is a
consumer.
28. The more closely related two species are the
more taxonomic categories they will share. The
more unrelated two species are, the fewer
categories they will share.
29. The first person to describe an organism in print
has the right to name the organism. However,
the new name must follow an international code
of rules for scientific naming. Latin is still used
in scientific naming because it is used in science
in all countries of the world.
30. Some scientists estimate that there are more
than 3 million species of insects. Not all living
things have been discovered. Over 1000 new
species of plants and animals are found,
identified, described, and named each year.
Most of the new species discovered come from
tropical areas.