Transcript Chapter 18: Classification

Chapter 18:
Classification
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18–1 Finding Order in Diversity
 Life
on Earth has been changing for
more than 3.5 billion years
 1.5 million species named
 between 2 and 100 million additional
species have yet to be discovered
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Why Classify?
 organize
living things into groups
that have biological meaning
 Taxonomy
= discipline of classifying
organisms and assigning each
organism a universally accepted
name
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Assigning Scientific Names
 Common
names are confusing and vary
among languages or even regions
– Ex: cougar, mountain lion, panther, puma
– different species sometimes share a single
common name
 Ex:
buzzard: hawk? Vulture?
 Scientists
have agreed to a single
name for each species
 Use Latin & Greek
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Binomial Nomenclature
 Carolus
Linnaeus,
– a Swedish botanist, 1700s

binomial nomenclature = classification
system in which each species is
assigned a two-part scientific name
– written in italics
– first word is capitalized, the second word
is lower case
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Scientific Names
 grizzly
bear is called Ursus arctos
– Ursus — is the genus
 Genus
= group of closely related species
– arctos – is the species
 unique
to each species within the genus
 Often a Latinized description of some
important trait of the organism or an
indication of where the organism lives
– Ursus maritimus, the polar bear
 maritimus,
referring to the sea
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Linnaeus's System of Classification
 Hierarchical
- it consists of levels
 includes seven levels
– from smallest to largest—species, genus,
family, order, class, phylum, and kingdom.
– Each level is called a taxon or taxonomic
category
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Ursus arctos (Grizzly Bear)
 Kingdom
– Animalia
 Phylum – Chordata
 Class – Mammalia
 Order – Carnivora
 Family –Ursidae
 Genus –Ursus
 species - arctos
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Humans
 Kingdom
= Animalia
 Phylum (Division for plants) = Chordata
 Class = Mammalia
 Order = Primates
 Family = Hominidae
 Genus = Homo
 species = sapiens
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 Taxonomic
groups
above the level of
species are “invented”
by researchers who
decide how to
distinguish between
one genus, family, or
phylum, and another.
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 Phylogeny
= the study of
evolutionary relationships among
organisms
 Biologists now group organisms into
categories that represent lines of
evolutionary descent, or
phylogeny, not just physical
similarities.
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 evolutionary
classification = method
of grouping organisms together
according to their evolutionary
history
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 The
higher the level of the taxon, the
farther back in time is the common
ancestor of all the organisms in the
taxon.
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 Cladogram
= diagram that shows the
evolutionary relationships among a
group of organisms
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 The
genes of many organisms show
important similarities at the
molecular level.
 Similarities in DNA can be used to
help determine classification and
evolutionary relationships.
 The more similar the DNA sequences
of two species, the more recently
they shared a common ancestor, and
the more closely they are related in
evolutionary terms.
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Dichotomous Key
A dichotomous key is a tool that allows
the user to determine the identity of items
in the natural world, such as trees,
wildflowers, mammals, reptiles, rocks, and
fish.
 Keys consist of a series of choices that
lead the user to the correct name of a
given item.
 "Dichotomous" means "divided into two
parts". Therefore, dichotomous keys
always give two choices in each step.

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18–3 Kingdoms and Domains
 There
are now 6 Kingdoms – listed
below.
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 Domain
= most inclusive taxonomic
category; larger than a kingdom
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Eubacteria
 Unicellular
 Prokaryotic
 Autotroph
or heterotroph
 Cell walls with peptidoglycan
 Examples: E. coli, Streptococcus, Staph
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Archaebacteria
 unicellular
 prokaryotic
 extreme
environments
– volcanic hot springs, brine pools, and
black organic mud totally devoid of
oxygen
 Auto
or heterotroph
 cell walls lack
peptidoglycan
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Protista
 eukaryotic
 greatest
variety
 Most single-celled, some multi
 photosynthetic or heterotrophic
 Ex: kelp, amebas, slime mold,
paramecium, euglena
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Fungi
 heterotrophs
– feed on dead or decaying
organic matter
 Eukaryotic
 Most
multicellular, some uni
 Cell walls of chitin
 EX: mushroom, yeast
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Plantae
 multicellular
 photosynthetic
autotrophs
 Eukaryotic
 Cells
walls of cellulose
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Animalia
 multicellular
 heterotrophic
 Eukaryotic
 No
cell walls
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