Download Classification

Classification
Chapter 17, Sections 1 and 4
Why classify?
Provides a way to
organize living things
 Ensures scientists are
using a common
language when talking
about living things

How are Things Classified?
Old way – by physical similarities
 New way – by molecular (DNA, RNA,
amino acid) similarities
 Increased understanding about DNA
has caused some revisions

Who & When: Development of
Today’s Classification System
Carolus Linnaeus a Swedish botanist
 During mid-1700s
 Only 2 kingdoms –
plants and animals

Levels of Classification
From broadest (biggest)
group to most specific
(smallest):







Kingdom
Phylum
Class
Order
Family
Genus
Species

There are many mnemonic
devices to help you
remember these levels;
write down your favorite or
make up a new one:
______________________
______________________
______________________
______________________
______________________
______________________
Rules for Scientific Naming
Each species’ name is unique and
usually descriptive
 Scientific names:

Latin or Latinized words
 Genus and species name
 This is called binomial nomenclature
(two-name naming)
 Genus name is capitalized
 Species name is all lowercase
 Both words are italicized or underlined

Two Kingdoms

Up until the 1950s – 1960s, most
textbooks still only referred to two
kingdoms:
Plants, which included all bacteria and
fungi
 Animals, which included all protozoa
(single-celled, eukaryotic organisms)

Five Kingdoms

In 1959, Whittaker developed the 5Kingdom system
Monera included all of
the prokaryotes (cells
without nuclei); all
others were eukaryotic.
Six Kingdoms

More recently,
scientists split
the kingdom
Monera into two
distinct groups
(Eubacteria &
Archaebacteria),
creating 6
Kingdoms
Kingdoms of Life, cont’d
These six kingdoms
have now been
grouped under a
higher category:
domain
 There are 3
domains:

Bacteria
 Archaea
 Eukarya

Characteristics of Each Kingdom
Characteristic
Archaebacteria
Bacteria
Protista
Fungi
Plantae
Animalia
Cell Type
(prokaryotic or
eukaryotic)
Prokaryotic
Prokaryotic
Eukaryotic
Eukaryotic
Eukaryotic
Eukaryotic
# of cells (uni or
multicellular)
Unicellular
Unicellular
Unicellular &
Multicellular
Unicellular &
Multicellular
Multicellular
Multicellular
Presence or
absence of
nucleus in cell
Absent
Absent
Present
Present
Present
Present
Presence or
absence of cell
wall
Present
Present
Present in
some
Present
Present
Absent
Cell wall
composition
No
peptidoglycan
Peptidoglycan
Varies
Chitin
cellulose
n/a
Mode of nutrition
(hetero /
autotrophic)
Autotrophic &
heterotrophic
Autotrophic &
heterotrophic
Autotrophic &
heterotrophic
Heterotrophic
Autotrophic
Heterotrophic
Presence or
absence of
locomotion
Present in
some
Present in
some
Present in
some
Absent
Absent
Present
Dichotomous Keys
Dichotomous keys are used to
distinguish between organisms that are
closely related.
 At each step on the key, the user is
given two choices. Each alternative
leads to another question, until the
organism is identified.

Sample Dichotomous Key
This simple example of a
dichotomous key shows
how each “question” must
be a yes / no question that
divides the organisms into
two groups.
Sample Dichotomous Key