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Biodiversity
Unit 1
Classification and
Diversity
What you ought to know
Why Classify?
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Huge diversity among organisms
1 organism can have different names (>1)
1 name can be given to different organisms
Avoids confusion due to language/cultural
variation
Describe a situation where classification has
affected your life.
Classification systems provide a
framework for examining existing
living organisms and a method for
comparing modern organisms with
extinct forms
Importance of Classification
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Recognition - organize and group things to avoid
confusion between objects, ideas, and events.
Serves as a basis for identifying known organisms and
unfamiliar organisms newly discovered
Gives order and logic to groups of related objects
Groups/categories are called taxa
The science of classification is taxonomy
Scientists who carry out this work are taxonomists
Modern Taxonomy
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Binomial Nomenclature
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Devised by Carolus Linnaeus (1707-1778)
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System of rules for naming organisms based on
physical and structural features of the organism
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The more features organisms have in common the
closer the relationship
Binomial Nomenclature
Two-part latin name
Genus + species
Noun + adjective
Ex) Ursus horribilis
*species is never used alone
Basic unit of classification
Which organisms are most closely
related?
Advantage to binomial
nomenclature:
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Indicates similarities in anatomy, embryology,
and likely evolutionary ancestry
Ex) grizzly bear
Ursus horribilis
polar bear
Ursus maritimus
*koala bear
Phascolarctus cinereus
* not considered a true bear
Dichotomous Keys
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Used in identification of organisms
The key is constructed so a series of choices
leads to a specific branch of the key.
If the choices are made accurately the
taxonomist is led to the name of the
organism being identified
Example
Levels of Classification
Kingdom
Phylum
Class
Order
Family
Genus
Species
Example: Butterflyweed (Asclepias tuberosa)
Kingdom: Plantae (All plants)
Phylum: Angiospermophyta (All
flowering plants)
Class: Magnoliopsida (Dicotyledons)
Order: Gentianales (All plants with united
petals and fused reproductive parts)
Family: Asclepiadaceae (Plants
with a specific pattern of fused repro. floral
parts)
Genus: Asclepias (All milkweeds)
Species: tuberosa (a specific kind
(species) of milkweed with orange flowers and
tuberous roots)
How many kingdoms should there be?
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Historically, biologists used a two kingdom
system PLANTS and ANIMALS
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This worked well until microscopic organisms
were discovered that displayed characteristics
of both kingdoms
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Kingdom Protista was added
And then there were six….
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Not long after, it was noted that bacteria and blue-green
algae lacked a true nucleus
Kingdom Monera was established as the only kindgom
of prokaryotic organisms (all other kingdoms contain
eukaryotes)
In the 1970’s work by Carl Woesz on the RNA of
bacteria led to a general agreement that the Monerans
be divided into two separate kingdoms, the Bacteria and
Archaea
The scientific community’s acceptance of this is still
cautious.
There’s a fungus amoung’us!
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In the plant and animal kingdom system,
anything that was not an animal was a plant
Recently taxonomists established the kingdom
for Fungi due to significant differences from
plants:
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Life cycle
Structure
Reproduction
Phylogeny and Modern Taxonomy
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Early biologists believed that living things
were fixed and unchanging
The modern view is that organisms changed
over time and evolution is accepted as the
basis for classification
Phylogeny is the evolutionary history of an
organism determined by radioactive dating,
comparative biochemistry, physiology and
DNA studies.
Phylogenetic tree (Nelson p.423)
5 Kingdoms versus 3 Domains???
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The three domain system of biological
classification was introduced by Carl Woesz to
reflect his discovery that the prokaryotes
comprise two very different groups of organisms.
In it, all living things are grouped into three
domains.
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Two of these, the Bacteria and Archaea (originally
Eubacteria and Archaebacteria), include prokaryotes.
The third, the Eukarya or Eukaryota, includes all
eukaryotes, including the older kingdoms Animalia,
Plantae, Fungi, and Protista.
These domains are typically
divided into kingdoms
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Other ranks higher than kingdom had been used
earlier (for instance empires) to group together the
eukaryotes, but in these schemes the prokaryotes
were retained as a single group.
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Some have argued that such systems are actually
preferable and that the differences between Bacteria
and Archaea are not sufficient to warrant such a level
of separate treatment.
Cladograms
Two approaches to classification:
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phenetics - a method of classifying organisms that is
based on their overall similarity in physical characteristics
or other observable traits (it does not take phylogeny into
account)
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Linnaean strategy
cladistics - a method of analysis (genetic analysis,
biochemical analysis, morphological analysis) that
determines relationships between organisms that are
based solely on their evolutionary history
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Phylogenetic strategy
Resources
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Classification website
Taxonomy
Games