Classification Notes
Humans like to group!
• We place things into
groups in order to
understand
relationships.
• Aristotle first
classified living things
in 350 BC.
http://www.stenudd.com/
myth/greek/aristotle.htm
Aristotle’s ideas were accepted
for 2,000 years!
• Animals were
grouped by habitat
& behavior.
• Plants were
grouped by size
and structure.
http://www.wisp.k12.wi.us/schools/mcki/
ANIMALS
LAND
AIR
WATER
PLANTS
HERB
SHRUB
TREE
Taxonomy
• Taxonomy: the science of
grouping organisms
• Taxa: Organisms within a
particular group
• In 1735 Carolus
Linnaeus devised a
system based upon
structural characteristics.
http://www.suite101.com/article
.cfm/paleontology/29306
Linnaeus created seven
Levels of Classification
•
•
•
•
•
•
•
Kingdom
Phylum
Class
Order
Family
Genus
Species
•
•
•
•
•
•
•
King
General
Phillip
Came
Over
For
Green
Spinach Specific
Linnaeus created a method for
naming organisms
• Binomial nomenclature: a
two-word system of naming
organisms
• Uses the genus + species
names
• Example: Humans = Homo
sapiens or Homo sapiens
– Always italicized or
underlined
– Genus capitalized
– Species with lower case
Linnaeus’
System
• Groups similar organisms
• Provides a standard system
for naming organisms
• New technologies
can change the
way we view
science…
• Domains have
been placed
above kingdoms
(1996).
Three Domains of Life
Domain Bacteria
- True bacteria; prokaryotic
Domain Archaea
- Ancient bacteria; prokaryotic
Domain Eukarya
- Eukaryotic; plants, animals, fungi,
& protist
Cladistics
A phylogeny, or evolutionary tree,
represents the evolutionary relationships
among a set of organisms or groups of
organisms, called taxa (singular: taxon).
The tips of the tree represent groups of
descendent taxa (often species) and the
nodes on the tree represent the common
ancestors of those descendents. Two
descendents that split from the same node
are called sister groups.
Evolutionary trees depict clades. A clade
is a group of organisms that includes an
ancestor and all descendents of that
ancestor. You can think of a clade as a
branch on the tree of life.
Cladistics is a method of hypothesizing
relationships among organisms. The basis
of a cladistic analysis is data on the
characteristics, or traits, of the organisms
in which we are interested. These
characters could be anatomical and
physiological characteristics, behaviors, or
genetic sequences.
Activity
Cladistics of Vehicles
Example
1. Choose the taxa. You decide to study
the major clades of vertebrates.
2. Determine the characters. After
studying the vertebrates, you select a set
of traits, which seem to be homologies,
and build the following data table to
record your observations.
3. Determine the polarity of characters.
From studying fossils and outgroups
closely related to the vertebrate clade,
you hypothesize that the ancestor of
vertebrates had none of these features.
4. Group taxa by synapomorphies. Since
we have a good idea of what the ancestral
characters are, this is not so hard. We
might start out by examining the egg
character. We focus in on the group of
lineages that share the synapomorphic
form of this character, an amniotic egg,
and hypothesize that they form a clade.
5.Work out conflicts that arise. There are
no conflicts here. Every group is a subset
of another group
6.Build your tree. Based on the groupings
above, you produce this tree: