Transcript Classification notes

The Tree of Life Ch 17
Taxonomy
• Science of naming and classifiying
organisms
• Based on physical and structural similarities
• A group of organisms in a classification
system = taxon
Binomial nomenclature
• System that gives each species a 2-art
name using Latin words
• Swedish botanist Carolus Linnaeus
introduced this naming system!
7 Levels of Classification
• The Linnaean
system has 7
levels or taxa
(from general to
most specific)
• Kingdom, phylum,
class, order,
family, genus, and
species
Limitations to Linnaean
System
• Created before technology allowed us
to study molecular level of organisms
• Based on physical similarities.
• We now know unrelated species can have
similar traits due to convergent evolution
• Genetic research now also plays a role
Example
• The Red panda is more closely related
to raccoons than to giant pandas
Dichotomous Keys
• Used to identify objects
or organisms that have
already been described
by another scientist.
• Made up of paired
statements.
• As you proceed from one
step to another, the
system narrows down
your choices until you
have identified the
organism
Classification Based on
Evolution
• Scientists agree species should be classified
based on evolutionary relationships, not just
physical similarities
• Cladistics- classification based on common
ancestry
• Uses fossil record, molecular data, and living
species as evidence
• Phylogeny- evolutionary history for a group of
species
Cladogram
• Evolutionary tree that proposes how
species are related to each other
through common ancestors.
Molecular Clocks
• 1960s- biochemists Linus Pauling and Emile
Zuckerkandl proposed a new way to measure
evolutionary time
• Compared amino acid sequences of hemoglobin
from wide range ofspecies
• Showed that more distant species had more amino
acid differences
• Molecular clocks are models that use mutation
rates to measure evolutionary time
Mitochondria DNA
• Mutation rate of mitochondria DNA is
about 10x faster than nuclear DNA
• Good method (molecular clock) for closely
related species
• Inherited from mom
• Used to study migration routes of humans
over the past 200,000 years
Domains and Kingdoms
• New evidence has
altered our
classification system
• In 1866 there were
only 3 kingdoms
(animal, plant and
protist)
• By 1977- living
things were
separated into 6
kingdoms
Domains
• 1977 Carl Woese revealed 2 genetically
different groups of prokaryotes
(splitting kingdom Monera into bacteria
and archaea)
• Because these bacteria were so
different from each other, he proposed
all life be divided into three domains
• Bacteria, Archaea and Eukarya
Domains
• Bacteria- single celled prokaryotes
• Archaea- single celled prokaryotes that live in
extreme environments (deep sea vents, hot
springs, antarctic waters, salt lakes)
• Eukarya- any living thing made of eukaryotic
cells (single-celled Protists, colonial and all
multi-cellular life)
Updated Classification Order
• Domain, kingdom, phylum, class, order,
family, genus and species
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