Notes: Classification of Living Things
Scientists have discovered and named over _______________________________ different organisms, and the list continues to
grow every day.
__________________________________ is a way of grouping things into categories based upon their characteristics.
The science of classifying all living things is called __________________________________. The way we classify organisms is
based upon a system developed over 200 years ago by Carolus Linnaeus.
According to his system, organisms are placed into groups called _________________. Linnaeus created 7 taxa:

Kingdom
 Phylum
 Class

(__________________________________)
Order

Family
 Genus

Species
(__________________________________)
A large number of organisms belong to the same kingdom. Fewer belong to the same phylum, and so on.

Species is the smallest , most ______________________ category. Organisms of the same species are a group of
genetically distinct organisms.

Two organisms in the same genus are quite similar because they diverged (came from) a recent common ancestor.
However, some form of selection in the past caused them to separate into different groups or species.
The diagram below shows Linnaeus’s classification of a grizzly bear starting with its Kingdom.
Notice the diversity of the organisms that are in the same kingdom as the grizzly bear.
o How many taxa do the fox & grizzly bear have in common? ___________
o If two organisms are in the same phylum, does that mean that they must be in the same class? ___________
o Which animal in the diagram is most closely related to the grizzly bear? _______________________________
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How we define a species?
As we learn more about the organisms around us, the definition for a species has changed over time.
If we have two organisms that look alike, how do we know if organisms are the same species? Scientists use several
characteristics to determine this.
A species is defined as organisms that:
1. Have a similar shape/structure (morphology). Organisms of the same species don’t have to be
identical. Many species have great variation in their appearances. Some examples include:

Ex: ____________________________________________________________________________

Ex: ____________________________________________________________________________
2. Are able to mate AND produce fertile offspring. Two giraffes reproduce and give birth to a baby
giraffe. Once that giraffe matures, it will reproduce and have babies of its own.
 A ___________________________ & a donkey have a similar appearance. When mated, their
offspring is a mule. As it turns out, mules are sterile and can’t reproduce. While both the horse
& donkey are in the genus Equus, they are classified as two ______________________ species.
3. The organisms must be a natural population. That means if the only time these animals might be
found together is in captivity, they would not be the same species.
 ________________________ & ________________________ belong to the genus Panthera. In
nature they are found on different continents. Sometimes in captivity, these animals have been
known to mate and produce offspring called a Liger or a Tigon (which are often sterile).
o
Liger = Lion (male) x Tiger (female)
o
Tigon = Tiger (male) x lion (female)
Linneaus realized that referring to organisms by their common name could be quite confusing.
While some common names refer only to one specific species (i.e. Lion and Walrus); Other common names
refer to many different species (there are 34 different species of _________________)
Linnaeus realized that each species needed a universal scientific name. These names were made up of
the last two taxa (______________________________ + ________________________________).
Each scientific name is unique for that species. These names are in _____________________ so they often
sound unusual to us:
The scientific name for humans is ___________________________________.

All humans are in the genus _____________________ and species name ________________________.
Kingdom Animalia
 Phylum Chordata
 Class Mammalia
order Primate
 family Hominidae
 genus Homo
 species sapiens.
Full Classification
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Today, the system has been modified in several ways:
1 – Based upon ______________________________ evidence, the classification of some organism had to
be changed. We are more accurately able to tell how closely related organisms are by comparing their
______________ or _______________________________.
2 – A larger taxa (classification group) was added to the system called ______________________________.
Organisms are placed into one of three domains based upon the complexity of their cells
prokaryotes = no nucleus
eukaryotes = nucleus
Within each domain, organisms are placed into a _________________________.
Organisms in the same kingdom share several important characteristics such as cell structure or
how they obtain and use energy (heterotrophs = eat autotrophs = make own food).
Classification Groups from biggest to smallest (broadest to most specific)
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Study Guide: Introduction to Classification
1.
What is the scientific name of the grizzly bear? ______________________ ___________________
(refer to the chart on page 1 of your notes).
2.
What language is used to give scientific names to all living things? _____________________
3.
What is the genus of the red maple if its scientific name is Acer rubrum? _________________
4.
The largest group in the current system of classification is the __________________________ ; The
_________________ is the smallest classification group.
5.
Fill in the name of each missing taxonomic category on the right in the chart below:
Taxon
Green Frog
Mountain Lion
Domestic Dog
Human
Kingdom
Animalia
Animalia
Animalia
Animalia
Chordata
Chordata
Chordata
Chordata
Amphibia
Mammalia
Mammalia
Mammalia
Anura
Carnivora
Carnivora
Primates
Ranidae
Felidae
Canidae
Hominidae
Rana
Felis
Canis
Homo
clamitans
concolor
familiaris
Sapiens
Class
Family
Species
6.
↑
Which taxon (category) includes the most specific characteristics? __________________________
7.
Which taxon above includes a larger number of species, an order or a phylum? ______________
8.
What is the scientific name of the green frog? ___________________________________________
9.
Which taxa do all four organisms have in common? ______________________________________
10.
Which two organisms in the chart are the most closely related? ____________________________ &
__________________________________; How many taxa do they have in common? ____________
11.
Which animal is least closely related to the human? ______________________________________
12.
For two organisms to successfully mate (produce fertile offspring), they must be the same ______
13.
Which taxa is larger than a family, but smaller than a class? ________________________________
14.
Since all of these organisms are in the animal kingdom they must be in the same domain. What is the
name of the domain that they are classified in? ____________________________________
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Notes: Ways to Show Evolutionary Relationships
Cladogram (Phylogenetic trees) are used to show how organisms & their ancestors evolved from one another.



Organisms shown share a common ancestor (located at the bottom of the tree/branches).
The simplest (most primitive) animals will be at the base of the chart.
The most complex (or most highly evolved) will be at the top of the chart (farthest from the base).
Use the cladogram to the right to answer the following questions:
1.
Which animal is the most primitive? ________________
2.
Does the perch possess a lungs? __________________
3.
What features are shared by the salamander & mouse?
_____________________________________________
4.
Why is the derived characteristic ‘feathers’ not written on the main
axis like all of the other characteristics?
____________________________________________
_____________________________________________
A Cladogram can be constructed for any group of organisms.

Use the cladogram on the right to answer questions 5-8.
5.
Which animals on the cladogram have limbs?
______________________________________________
6.
Which animal on the cladogram is the most complex?
______________________________________________
7.
What characteristic(s) is/are listed for the sponges?
______________________________________________
8.
Placenta
Hair
Limbs
Jaws
Segmented Body
What characteristics are shared by the lizard & the earthworm?
______________________________________________
Multicellular
Molecules reflect evolutionary relationships.
Comparing the _________ and _______________
(which are made of amino acids) of different
species provides strong evidence for evolution.
Finding the number of differences in the genetic
information between different species helps
determine how closely related two organisms are.
In the cladogram on the left, the greater the
evolutionary distance from humans, the greater the
number of amino acid differences in the
hemoglobin protein (polypeptide).
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Notes: Classification Keys (see pages 462-463 for additional information)
A classification key, also knows as a ___________________________________ key, is useful in
identifying unknown organisms (but is not limited to being used with living things).
Use the dichotomous key to identify the organisms by their scientific names.
Organism A
Organism B
Organism C
Organism D
______________
______________
______________
____________
______________
___________
______________
____________

Begin on line 1 (reading choices a and b). Choose the statement that matches your organism.

Follow the Go To directions until you come to a line that identifies the organism by name.
1a. organism with two or four functional legs . . .
1b. organism without two or four legs . . . . . . . . .
go to 2
go to 3
2a. organism without wings . . . . . . . . . . . . . . . . .
2b. organism with wings . . . . . . . . . . . . . . . . . . .
Canis familiaris
Passer domesticus
3a. organism is unicellular . . . . . . . . . . . . . . . . . .
3b. organism is multicellular . . . . . . . . . . . . . . . .
go to 4
go to 5
4a. organism swims freely in water . . . . . . . . . . .
4b. organism is anchored to substrate . . . . . . . . .
Balantidium sp
Stentor sp.
5a. organism is heterotrophic . . . . . . . . . . . . . . . .
5b. organism is autotrophic . . . . . . . . . . . . . . . . .
go to 6
go to 7
6a. organism lives in ocean . . . . . . . . . . . . . . . . .
6b. organism lives on land . . . . . . . . . . . . . . . . . .
Monodon monoceros
Ophiophagus hannah
7a. organism is a tree . . . . . . . . . . . . . . . . . . . . . .
7b. organism is an herb . . . . . . . . . . . . . . . . . . . .
Pinus ponderosa
Taraxicum officinale
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Practice Using a Dichotomous Key
Examine the drawings of the four leaves below. Use the key that follows to identify the leaves. Write the name of
each leaf in the numbered box below its picture.
Leaf A
Leaf B
Leaf C
Leaf D
12 cm long
6 cm long
1.
16 cm long
14 cm long
2.
3.
4.
Now use the dichotomous key – what can you tell me about the sugar maple?
5. Is the sugar maple star shaped? _____________________
6. Are its lobes pointed or rounded? ____________________
7. How many lobes does it have on each leaf? ____________
1a. oval leaf . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
1b. leaf deeply notched or lobed . . . . . . . . . . . . . . . . . . . .
go to 2
go to 5
2a. leaves with smooth edge . . . . . . . . . . . . . . . . . . . . . . . .
2b. leaves with serrate or “sawtooth” edge . . . . . . . . . . . .
go to 3
go to 4
3a. leaves 10 – 15 cm long . . . . . . . . . . . . . . . . . . . . . . . . .
3b. leaves 4 – 7 cm long . . . . . . . . . . . . . . . . . . . . . . . . . . .
magnolia
common pear
4a. leaves 10 – 15 cm long . . . . . . . . . . . . . . . . . . . . . . . . .
4b. leaves 4 – 7 cm long . . . . . . . . . . . . . . . . . . . . . . . . . . .
Spanish chestnut
white elm
5a. four or five lobes total . . . . . . . . . . . . . . . . . . . . . . . . . .
5b. many lobes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
go to 6
go to 7
6a. four pointy lobes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
6b. five pointy lobes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
tulip tree
go to 8
7a. lobes pointy . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
7b. lobes rounded . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
red oak
English oak
8a. star-shaped leaf . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
8b. leaf not star-shaped . . . . . . . . . . . . . . . . . . . . . . . . . . . .
sweet gum tree
go to 9
9a. long, narrow lobes . . . . . . . . . . . . . . . . . . . . . . . . . . . .
9b. each lobe having several points . . . . . . . . . . . . . . . . . .
Japanese maple
go to 10
10a. leaf longer than it is wide . . . . . . . . . . . . . . . . . . . . . .
10b. leaf wider than it is long . . . . . . . . . . . . . . . . . . . . . . .
pin oak
sugar maple
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Classification Review
Use the diagram to the right to answer the next two questions.
1. Which organism(s) on the right show segmentation?
_______________________________________________
2. What characteristic do all three organisms have in common?
________________________________________________
3. Most scientific names are written in _________________
(language).
4. The first word of each name is called the ________________.
The second word is called the _________________________.
5. Write the scientific name for humans - _______________________ ________________________.
6. The study of the classification of organisms according to their characteristics is ____________________.
7. List 3 characteristics that animals must have in order to be classified as being in the same species:
 _____________________________________________________________________________
 _____________________________________________________________________________
 _____________________________________________________________________________
8. List the three domains and tell which kingdoms are classified under each domain.
 _____________________________---____________________________________________
 _____________________________---____________________________________________
 _____________________________---____________________________________________
9. According to the classification system used today, list the eight TAXA from largest to smallest.
__________________  __________________  __________________  _________________ 
____________________ ________________________________________________________
10. A ___________________ ________________ key is also known as a two branching chart which can be used to
identify the name of objects or specimen.
Use the diagram shown on the left to answer the
questions 11-12:
11. What characteristic(s) are shared by the lungfish and
flounder? ______________________________________
12. Which animal(s) has/have amniotic egg? __________
______________________________________________
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