Classification and Dichotomous Keys

Bell work
Think about the different ways humans classify
things. List five groups of things that humans classify,
such as library books, department store merchandise,
and addresses. Is there such a thing as too much
classification? What happens when you put something
in the wrong group? Can objects or ideas belong in
more than one group at the same time?
Record your responses on your bell work sheet.
Classification and Dichotomous
• Classification: the division of organisms into
groups, or classes, based on specific
• Scientists classify organisms to help make sense
and order of the many kinds of living things in the
• Before the 1600’s scientists divided organisms
into two groups: Plants and Animals.
• Taxonomy: the science of describing,
naming, and classifying organisms.
• Taxonomists use an 8-level system to
classify living things based on shared
• Did King Phillip Come Over For Grape Soda?
Branching Diagram
• Shows relationships among various
biological species or other entities based
upon similarities and differences in their
physical or genetic characters.
Branching Diagram
Levels of Classification
• Every living thing is classified into 1 of 3
groups: Bacteria, Archaea, and Eukarya
• Then sorted into kingdoms, phylum, class,
order, family , genus, and then species.
Scientific Names
• Before Linnaeus simplified the naming of living
things, they could have had a name that was 12
words long.
• Two-Part name: Felis domesticus (common house
cat) 1st part of the name Felisis the genus name.
The 2nd part domesticus is the specific name.
• Naming rules help scientists communicate clearly
about living things.
Rules of Names
• All Genus names begin with a capital letter
• All specific names begin with a lowercase
letter “domesticus”
• Usually both words are underlined or
• Scientific names are usually in Latin or
Greek and contain info about the organism.
Dichotomous Key
• An aid that is used to identify organisms and that
consists of the answers to a series of questions.
• Using a D.K.: there are only two alternative
responses for each statement. From each pair of
statements, choose the statement that describes the
organism or is directed to another statement, until
the organism is identified.
Dichotomous Key
The Domain Archaea
(traditional Kingdom Archaebacteria)
• Archaea is one of the three
major divisions (domains).
• Once thought to be bacteria.
• Single-celled organisms
• One of two kinds of prokaryotes which
• means they do not have a nucleus.
• Most live in extreme environments like the hot
springs of Yellowstone because of their tough outer
cell wall and protective enzymes.
• Archaea have been around at least 3 billion years
and scientists believe they are very closely related to
some of Earth’s earliest life forms.
The Domain Bacteria
• Bacteria prokaryotic (no nucleus).
• Bacteria are single-celled.
• Bacteria can be found everywhere…in soil, water,
and even on and inside the human body. For
example, E coli is present in the human intestines
where it produces vitamin K. Another kind of bacteria
converts milk into yogurt.
• Some bacteria cause diseases (pneumonia) while
others make chemicals that help fight disease.
The Domain Eukarya
The Kingdom Protista
Members of the kingdom Protista commonly
called protists, are single-celled or simple
multicelluar organisms.
They are eukaryotic (have a nucleus).
Protista contains many kinds of organisms,
including protozoans, algae (plant-like),
slime/molds (animal-like), and euglenoids.
The Domain Eukarya, continued
The Kingdom Fungi
They are multicellular.
Fungi do not perform photosynthesis or eat food.
Instead, fungi break down surrounding stuff with
digestive juices and absorb the nutrients.
Molds and mushrooms are examples of the complex,
multicelluar members of the kingdom Fungi.
The Domain Eukarya, continued
The Kingdom Plantae
Consists of complex multicellular organisms.
They are eukaryotic (have a nucleus).
They have cell walls.
They make food through photosynthesis.
The Kingdom Animalia
The Domain Eukarya (continued)
The kingdom Animalia contains complex,
multicellular organisms that don’t have cell walls.
Most able to move around and have specialized
sense organs. However, an exception is the
sponge, a simple animal that cannot move.
Examples include ants, beetles, lizards, fish,
birds, apes, elephants, and more.
• On a half sheet of paper:
• List the 4 kingdoms we talked about today
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