The Tree of Life
Chapter 17 Notes
Rose
17.1- Early scientists named new found organisms
however they wanted and it was usually named
after the founder.
Taxonomy is Born
In the 1750’s, Carolus Linnaeus derived a standard way to
organize and name organisms:

Taxonomy is the science of naming and classifying
organisms.

Linnaeus, at the time, based all groupings on physical and
structural similarities.

Organisms are placed in different Taxons, which are
categories of classification.
The Scientific Name

Linnaeus also gave each organism a Scientific Name.

The scientific name was a two-part name. This idea is called Binomial
Nomenclature.

Scientific names are made up of the Genus and Species that the
organism belongs to.

The first part of the name is the Genus and the second part is the
Species.

ie.) Quercus alba = White Oak

ie.) Homosapien sapiens = Human

The Genus part of the name is always CAPITALIZED, and the species is
always lowercase.

The name is always in italics or underlined.
Why Scientific Names?

Mostly to avoid confusion between scientists.

For example, the Puma, Mountain Lion, and Cougar are all the same
cat, but are called different names in different regions.

However, if they use Puma concolor, Every scientist knows what cat is
being talked about.
Puma concolor ›
The System of Classification
Linnaeus’s Classification System had 7 levels or Taxons:
Kingdom -> Phylum -> Class -> Order - > Family -> Genus ->
Species(most specific)

Each section or taxon is “nested” with the taxon right
before it.
 ie.)
Kingdoms contain many Phyla, Phyla contain many
classes, etc.
 Pleases
Refer to Figure 1.3 in your book…
The System of Classification (con’t)

Linnaeus’s Classification system
does have limitations.

His system obviously focused
only on physical structures.

As we know now, physical
similarity (Analogous
Structures) don’t always mean
a close relationship.

Today’s technology allows us to
compare at a molecular level!
17.2- Classification Based on
Evolutionary Relationships

Similar traits often mean similar ancestors; however, scientists have
learned that similar traits can be because organisms are trying to fit
in the same environment.

This makes organisms look more and more alike even though they are
not related. This is called Convergent Evolutions:

Therefore, modern classification is based more on evolutionary
relationships and less on physical similarities.
Classification Based on Evolutionary
Relationships (con’t)

Many types of diagrams can show these relationships between
organisms. One of the most common is a Cladogram.

This is an evolutionary tree that proposes how species may be related
to each other through common ancestors.
Motor
Walking Bike Bike Car
Plane
Wings
Enclosed Passengers
Motor
Wheels
Classification Based on Evolutionary
Relationships (con’t)

As you can see, the diagram shows the relationship between all the
types of locomotives, but also shows how one evolved into another.
Interpreting a Cladogram:

Derived Characters – Traits that have come about over time: These
are shown as hashmarks between the branches.

Nodes – Each place where a branch splits.

Clades – Are groups of organisms that share common ancestors
17.4- Domains and Kingdoms

Classification is an ever-changing science. New discoveries lead to
changes in the classification system. Changes have included:

Two kingdom (plant and animal) until 1866 when kingdom Protista was
found

1938 - Prokaryotes (bacteria) got their own kingdom because they are
only organisms with no nucleus

1959 – Fungi got own kingdom based on how they feed

1977 – Bacteria split into 2 different kingdoms based on different genes
Domains and Kingdoms

From all these findings, scientists proposed a new taxon bigger and
more general than kingdom. It is called a Domain.

There are 3 domains:
1.
Domain Bacteria – Single celled prokaryotes in Kingdom Bacteria
(Kingdom Bacteria)
2.
Domain Archaea – Single celled prokaryotes in Kingdom Archaea
(Kingdom Archaea)
3.
Domain Eukarya – All organisms that have nuclei in their cells. Includes
all other kingdoms and organisms except bacteria. (Kingdoms Protista,
Fungi, Plantae, Animalia)