Download 5.3 Classification NOTES File

CLASSIFICATION
&
BIODIVERSITY
Why Classify ?
•The world is populated by
at least 10 million different organisms.
•To ensure accurate communication about
organisms, biologists use
• Taxonomy is the branch of biology that names
and groups organisms according to their
characteristics and
Early Classification Systems
•Aristotle (over 2000 yrs ago) devised the first
classification system.
•grouped plants by size (small, med, large)
•grouped animals by habitat – land, water, air dwellers
•This was not a great system but it persisted
until Linnaeus (Swedish botanist) came up with
another one in the mid-1700’s
Linnaeus’ System
Linnaeus’s system relied
upon hierarchical
categories using mainly
the organism’s
morphology
().
Kingdoms expanded...
•As biologists learned more about the
natural world, they realized that two
kingdoms did not adequately represent all
the diversity of life.
Levels of
Classification
Scientists classify organisms
into seven basic levels
in the hierarchy
(expanded since Linnaeus):
kingdom, phylum, class, order,
family, genus, and species.
- Kingdom is the largest category
- Species, the smallest grouping.
The placement of species is meant to
indicate.
Why group organisms at all?
•Make sense of life on Earth
•Predict characteristics shared by
members of a group
•Show
(since Darwin’s time)
Why Binomial
Nomenclature?
•There is confusion about
common names:
•Ex. This cat’s common name:
•mountain lion; puma; cougar; panther;
jaguar
•These two birds are both called
“robins”
To avoid this confusion
scientists assign each species
a unique.
Biological Naming of Species
• Binomial nomenclature is a system developed by Linnaeus that
consists of two-part names for each organism.
• The scientific name consists of the genus and species. It is
italicized when typed or underlined when handwritten.
(“species” is sing/plural -- “genera” is plural for “genus”)
•Genus - Capitalized; species - not capitalized
•standard throughout the world (unlike common name)
•in Latin (or Greek) - the scientific language of the day
•unique to the organism
•Naming rights of new species go to lead scientist on the
team (i.e. Dracorex hogwartsia)
What is the scientific name of these two organisms?
Bobcat:
Lion:
Kingdom
Phylum
Class
Let’s try
humans...
Order
Family
Genus
Species
Binomial
Kingdom
Now find
another
organism
from the
plant
kingdom
Phylum
Class
Order
Family
Genus
Species
Problems with Classification
•Because of convergent evolution,
analogous characters sometimes
make it seem like unrelated
organisms are related
•Ex. These vultures and plants are
unrelated and from different
continents.
•To solve this problem, taxonomists
now make use of etc.
•Taxonomists have developed a
way to build family trees (called
cladograms) which show the
evolutionary relationship
between species.
•These are made by finding
shared derived characteristics
between species. ()
•These characteristics are
placed on the cladogram where
they first developed – all
organisms that evolved after
that point have the
characteristic.
Cladistics
Kingdoms vs. Domains
•
As biologists learned even more about
the natural world, they realized the bulk
of life on Earth were bacteria.
•
•
•
Bacteria: common simple single
cells: (prokaryotes)
Eubacteria: simple single cells living
in harsh environments (prokaryotes)
Eukaryotes: includes some single
celled (but more complex organisms)
and ALL multicellular life
Three Domain System
•More recently, comparing sequences of ribosomal RNA in
different organisms has helped scientists determine that
living organisms seem to fall into three broad groups or
domains.