ch 1 lecture sp 11
TRANSCRIPT
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Classification and the
Tree of Life
CHAPTER 1 REVIEW
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The Tree of Life
The cell theory and the theory of evolution by naturalselection imply that all species come from preexistingspecies
all species, past and present, trace their ancestry back to asingle common ancestor.
The tree of life is a family tree of organisms that describes
the genealogical relationships among species with a singleancestral species at its base
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Speciation
a divergent process in which natural selection has causedpopulations of one species to diverge to form new species
Species
Populations of individuals which can interbreed to produce fertileoffspring
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Linnaean Taxonomy
Taxonomy is the effort to name and classify organisms.
In Linnaeus taxonomic system for classifying organisms,each organism is given a unique two-part scientific name
consisting of the genus and the species. A genus is made up of a closely relatedgroups of species.
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Taxonomic Levels Linnaeus system is hierarchical with nested taxa.
The taxonomic levels from least to most specific are as follows:
kingdom
phylum
class
order
family
genus
species
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Linnaeus
TaxonomicLevels
KINGDOM
(Animalia)
PHYLUM
(Chordata)
CLASS
(Mammalia)
ORDER
(Primates)
FAMILY
(Hominidae)
GENUS
(Homo)
SPECIES
(Homosapiens)
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How Many Kingdoms Are There? Linnaeus proposed just two kingdomsplants and animals.
However, not all organisms fall neatly into these categories.
An alternative five-kingdom system was proposed in the 1960s
Monera
Protista Fungi
Plantae
Animalia
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The Origin of the Phylogenic Tree of Life
Carl Woese and colleagues studied small subunit rRNA, as ameans for understanding the evolutionary relationships amongorganisms
(1) rRNA sequences should be very similar in closely relatedorganisms but less similar in organisms that are less closelyrelated.
(2) A phylogenetic tree reflects these relationships among species.Branches that are close to one another represent species thatare closely related; branches that are farther apart represent
species that are more distantly related.
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Changes to the Tree of Life Recent evidence indicates three major groups of organisms: One group of eukaryotesEukarya
Two groups of prokaryotesBacteria (everyday bacteria) and Archaea(extremophile bacteria)
Therefore, Woese created a new taxonomic level called the domain,consisting of
Bacteria
Archaea
Eukarya
The location of certain branches on the tree is hotly debated and theshape of the tree will continue to change as databases expand.
Which group do you
think is more
closely related to
the eukaryotic
kingdoms (yellow?)
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Phylogenetic Tree of Life
Plants, fungi, and
animals are small
branch tips on
the tree of life
This node represents the common
ancestor of archaea and eukaryotes
This node represents the common
ancestor of all organisms alive today