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Chapter 18 Classification and Systematics (Cladistics (Understanding…
Chapter 18 Classification and Systematics
Concept
phylogeny
hereditary relationship of any group of organisms constitute
basically the evolutionary history of each member of the group
systematics
goal of modern plant
understand each of these evolutionary lines
have a system of names
nomenclature
reflect their relationship accurately
natural system of classification
system in which closely related organisms are classified together
assigning plant names on the basis of phylogenetic relationships
Levels of Taxonomic Categories
species
ideally and theoretically is set of individuals closely related by descent from a common ancestor
binomial system of nomenclature
every species have both a genus name
species epithet
the basis of our present
inheritance of acquired characteristics
unfortunately J.B.P. de lamarck at this time presented his theory of evolution
monophyletic
critical concern is the genera are natural
all of species included in the genus are related to each other by a common ancestor
all descendants of that common ancestor are in the same genus
Cladistics
Understanding Cladograms
cladogram
diagram that shows evolutionary patterns by means of a s series of branches
common ancestor
represents the divergence of one taxon into two
all of the branches that extend from any particular point represent the descendants of the original group
two branches
white flowers are derived conditions
apomorphy
red flowers
ancestral condition
parsimony
simplest possible hypothesis
do not make a hypothesis any more complicated that it need to be
unresolved polychotomy
sometimes there is simply not enough data
usually the various species are shown as arising from the same node
Cladograms and Taxonomic Categories
basal angiosperms
have not been given a formal taxonomic name
eudicots
rest of the dicots
informal name
cladistics
method of analyzing these phylogenetic
evolutionary relationships
synapomorphies
homologous features
similar to each other b/c they have descended from a common ancestral feature
homoplasies
should never be used to conclude that plants are closely related
analogous features
Other Types of Classification Systems
Artificial Systems of Classification
several key characters
often very easy to observe
chosen as the basis of classification
Classification Systems for Fossils
form genera
all fossils with the same basic form
structure are classified together
third type of classification
used for fossil organisms
combines features of both artificial&natural systems
Taxonomic Studies
isotypes
prevent a recurrence of disaster
other specimens
as similar as possible to the type specimen
sent to many herbaria around the world
The Major Lines of Evolution
grade classification
old classification of protista
as opposed to a clade
"protistans" were placed together b/c they had a low level of evolutionary advancement
kingdom plantae
early algae continued to diversity
approximately 400 million year ago
some became adapted to living on land
establishing the clade of true plants
all organisms are grouped into three domains
Bacteria
with cyanobacteria
Archaea
Eukarya
