Why do we classify things? Finding Order in
Diversity
Classification provides scientists and students a
way to sort and group organisms for easier study.
Taxonomy – branch of biology that deals with the
classification and naming of living things
There are millions of organisms on the earth!
(approximately 1.5 million have been already
named)
Classifying and Naming Organisms
1. Grouping organisms based on comparing
characteristics makes it easer to study the
diversity of live.
2. Binomial Nomenclature – 2 word system of
identifying each kind of organism; avoids
confusion
A. Carolus Linnaeus – founder of modern
taxonomy; used structural similarities as a
basis for his classification system
Carolus Linnaeus
Why do biologists
consider Linnaeus’s
system an improvement
over earlier systems?
Classifying and Naming Organisms
1. Binomial Nomenclature (cont.)
B. Scientific Name – both names together
i. 1st name – genus (always capitalized)
ii. 2nd name – identifies species within
the genus (lower case)
iii. Name is written in italics or
underlined
Linnaeus’s
Classification
System –
hierarchical system
from most inclusive
to least inclusive
are:
This
illustration
shows how a
grizzly bear,
Ursus arctos,
is grouped
within each
taxonomic
category.
Go to Fig. 18-4
What do the
scientific
names of the
polar and
grizzly bears
tell you about
their
similarity to
each other?
Linnaeus’s system was limited because similarities
and differences were mainly visible
What was invented that helped to change the way
scientists classify organisms?
Evolutionary classification based on Darwin’s
Theory of Evolution – Decent with Modification
Species gradually change, or evolve, over time from
pre-existing species
Classifying species based on easily observed adult
traits can pose problems. Which of these
organisms seem most alike?
Cladograms – a diagram that shows evolutionary
relationships among organisms based on
shared derived characters (Fig. 18-7)
Structural – ex. Skeletal structure, leaf anatomy
Structural – ex. Skeletal structure, leaf anatomy
Behavioral – similar behaviors may indicate a close
relationship – Fig. 18-8
American and African vultures look very much
alike and were once classified together.
American vultures have a peculiar behavior:
When they get overheated, they urinate on their
legs to cool down. The stork is the only other
bird known to behave this way.
Biochemical – information about DNA, RNA &
proteins can be used to help determine
relationships and can be used to estimate how
long different species have been separated
African Vulture
American Vulture
Wood Stork
Cytological – cellular structure – ex. Prokaryotic vs.
eukaryotic, plant cell vs. animal cell
Embryological – early stages of development may
show shared characteristics that are absent at
the adult stages (Fig. 15-17 pg. 385)
Fossil Formation – establish relationships between
modern-day species & those that lived years ago
http://www.pbs.org/wgbh/nova/tech/radiocarbondating.html?elq=c91efd4570264eeb936ce73b956e
a24e&elqCampaignId=155
Arranging the diversity of life into the highest taxa
is a work in progress. What is important to
understand is that new information has
reopened issues concerning biological
diversity. Fig. 18-11
Domains – the most inclusive categories, assigns
more significance to the ancient evolutionary
split between bacteria and archaea
Bacteria unicellular,
prokaryotic, cell
wall contains
peptidoglycan,
ecologically diverse
(free living or
parasitic; autotroph
or heterotroph;
anaerobic or
aerobic)
Archaea – unicellular, prokaryotic, cell wall lacks
peptidoglycan, most live in very extreme habitats
that are devoid of oxygen
Eukarya – consists of all organisms that are
eukaryotic; Kingdoms of this domain include
a. Protista
b. Fungi
c. Plantae
d. Animalia
Fungi – Eukaryote, Cell walls of chitin, Most
multicellular; some unicellular; Heterotroph
Fungi – Eukaryote, Cell walls of chitin, Most
multicellular; some unicellular; Heterotroph
Protista – Eukaryote, cell walls of cellulose in
some; some have chloroplasts; most
unicellular, some colonial, some multicellular
Plantae – Eukaryote, cell walls of cellulose;
chloroplasts, multicellular, autotroph
Animalia – Eukaryote, no cell walls or chloroplasts,
multicellular, heterotroph