Transcript MODERN TAXONOMY

Taxonomy
Techniques of the past and
present to provide information
about an organism.
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Part One
How it all started.
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TAXA
• Greek word meaning categories or groups .
• Singular form of the term is taxon.
• Taxonomy: the science that deals with the
classification or grouping of living things.
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The first classification system
• 400 B.C. - Greek philosopher, Aristotle,
developed a system for sorting living
organisms.
• His system consisted of two kingdoms; the
plant and animal kingdoms.
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Plants were grouped according to their
stem structure and size. The 3 subgroups
were:
Shrubs
Trees
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Animals were grouped according to habitat:
Land
Water
Air
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Gradually Aristotle’s system showed
weaknesses. Can you identify any?
• not specific enough
• too many organisms were being discovered
• The microscope discovered many organisms that
would not fit into Aristotle’s classification system.
• NOTE: despite its weaknesses this first
classification system was used for about 2,000
years.
• Who improved on this old system?
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Beginnings of
Modern Taxonomy
• 1600’s
• John Ray - introduced a term called
species.
• Stated that a species was a group of
organisms that were:
• similar in structure
• able to mate and pass the traits to their
offspring.
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Founder of modern taxonomy
• Carolus Linnaeus (also in the 1600’s)
• Also used structural similarities as the
basis for his taxonomic system
• Started with a large group or kingdom
which he divided into subgroups
• Organisms could be sorted more
precisely
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Today’s taxonomy still uses Linnaeus’
system
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Example: human
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Kingdom
Phylum
Class
Order
Family
Genus
species
Animalia
Chordata
Mammalia
Primates
Hominidae
Homo
sapiens
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King
Philip
Came
Over
For
Green
soup
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Scientific Naming System
• There are always two Latin words to name each species.
• Process is called binomial nomenclature.
• Used world-wide to prevent confusion caused by various
languages.
• Prevents confusion with common names.
 Example: A puma, cougar and mountain lion are all the
same animal. Its scientific name, world-wide is:
Felis concolor
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More about scientific naming
• The scientific name is composed of the Genus and
the species.
• Rules for writing scientific names.
• Genus is given first and must be Capitalized and
underlined (or in italics)
• Species name is second and must begin with a lower
case letter and must be underlined (or in italics)
 Example: Homo sapiens or Homo sapiens
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Other examples of scientific names:
Cats
Genus - Felis
• Wildcat
• Felis sylvestris
• Cougar
• Felis concolor
• Housecat
• Felis domesticus or Felis
domesticus
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Review of the key terms
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Taxa
Taxonomy
Latin names
Aristotle
John Ray
Carolus Linnaeus
Species
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Kingdom
Phylum
Class
Order
Family
Genus
• Binomial Nomenclature
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Part Two
Modern Methods
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Today most scientists …….
• recognize that organisms have changed
over time.
• accept evolution as the basis for
classification.
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Phylogeny
(phy-log-e-ny)
The field of biology where scientists study
the evolutionary history of living
organisms.
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Phylogenists often study fossils.
1. Fossil Records: Fossils provide evidence that
show how plants and animals are related by
preserving structures that can be studied and
compared.
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What is a fossil ?
A cast or mold of an
organism preserved
in rock that formed
where the organism
died.
Trilobite
Fish
Archaeopteryx
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A fossil may also
consist of the
organism itself
preserved in ice,
amber, or in volcanic
glass.
Cockroach in amber
Firefly
Can you guess what
these are?
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A fossil may also consist of tracks (footprints),
seeds, or skeleton preserved in deposits
(sediments).
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2. Homologous Structures…
…are parts in different animals that show similarities
in their structure.
Ex.- a bat wing,
a human arm, a
whale flipper and
a cat foreleg are
all homologous
structures.
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3. Comparative Embryology
Taxonomists study the patterns of development
before birth. Embryos of organisms believed to
be closely related show similar patterns of
development.
Dolphin embryo
Human embryo
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Modern Methods (cont’d)
4. Comparative biochemistry: the study of the chemistry of
blood, enzymes and other specific substances produced
by animals and plants.
Example: hemoglobin in the blood cells of gorillas and
humans are the same except for one amino acid.
5. Comparing sequences of amino acids in organisms helps
to reveal relationships.
Q. What determines the sequence of these amino acids
?
A. DNA
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Modern Methods (cont’d)
6. Comparative DNA and RNA: Scientists now
study DNA and RNA structure to see their
similarities among organisms.
• DNA of humans and chimpanzees is 96% identical.
• DNA between humans and other mammals
(dog,horses,whales,bats,etc) is only about 80%
identical.
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Modern Methods (cont’d)
7. Function: what the organism does: its
place in the ecosystem.
8. Behavior: series of activities performed by
an organism in response to stimuli.
9. Nutrition: what an organism eats
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Final Thoughts
• It is important to recognize that a
taxonomic classification system is not a
fact.
• Classification is based on educated
opinions and as a result there are a
number of ways in which organisms
can be grouped.
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