The History of Organization

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The History of Organization

Aristotle 384-322 BC Interested in biological
classification. Patterns in nature.
Carl Linnaeus 1707-1778 ACE Father ofBiological
Classification!
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TaxonomyHow do we sort life?

• Taxonomy divides organisms into several
  categories that start out broadly and become more
  specific.

Kingdom Phylum Class Order Family
Genus Species Subspecies
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The Linnaean Hierarchical Classification System
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Taxonomy Assigning Names

• Rules
• Latin
• 1st name capitalized
• 2nd name lower case
• Italicized
• Ex. Homo sapiens

Kingdom Phylum Class Order Family
Genus Species Subspecies
Scientific Name
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TaxonomyRelationships
Kingdom Phylum Class Order Family Genus Species Su
bspecies
Animalia Chordata Mammalia Primates Homididae Homo
sapiens sapiens
Animalia Chordata Osteichthyes Salmoniformes Salmo
nidae Onchorhynchus tshawytscha
Plantae Pinophyta Pinopsida Pinales Cupressaceae S
equoia sempervirens
Human
King Salmon
Coast Redwood
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• Genera are grouped into progressively larger
  categories

Table 15.10
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Classification Categories

• The higher the category, the more inclusive
• Organisms in the same domain have general
  characteristics in common
• In most cases, classification categories can be
  subdivided into additional categories
• Superorder
• Order
• Suborder
• Infraorder

Order Chiroptera (Ky-ropter-a) (Gr. cheir, hand,
pteron, wing) Suborder Megachiroptera
(megabats) teropodidae Suborder
Microchiroptera (microbats) Superfamily
Emballonuroidea Emballonuridae (Sac-winged or
Sheath-tailed bats) Superfamily
Antrozoidae (Pallid bats) Molossidae
(Free-tailed bats)
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SPECIES Evolution creates (and destroys)
new species, but
What is a species?
Its not as straightforward a question as most
believe.
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What is a Species?
And these are all members of a single species.
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What is a Species?
The definition well use is this A species is a
group of individuals capable of interbreeding to
produce fertile offspring.
This is the biological species concept. Like all
attempts to define a species, it has many
problems.
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One Problem in the Biological Species Concept
For asexually-reproducing organisms, like these
bacteria, what constitutes a species?
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How Many Species Are There?
We dont know.
About 2 million species have been described.
Estimates of existing species number range from 4
million to 100 million (with 10-15 million being
a more commonly considered upper estimate).
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Species Come and Go
Best estimates from the fossil record indicate
that greater than 99 of species that have exited
are now extinct.
A typical lifetime for a species is about 1
million years.
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The Cretaceous/Tertiary Mass Extinction
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SYSTEMATICS AND PHYLOGENETIC BIOLOGY

• Systematists classify organisms by phylogeny
• Reconstructing phylogeny is part of systematics
• the study of biological
  diversity and classification

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Phylogeny

• Phylogeny often represented as a phylogenetic
  tree
• A diagram indicating lines of descent
• Each branching point
• Is a divergence from a common ancestor
• Represents an organism that gives rise to two new
  groups

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Evolutionary trends may reflect unequal
speciation or survival of species on a branching
evolutionary tree

• Phylogenetic trees strive to represent
  evolutionary history
• Phylogeny is the evolutionary history of a group
  of organisms, a description of the lines of
  descent of plants and animals as they lived from
  one era to the next.
• The most complete line discovered is of the
  horse.

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Figure 15.8
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Phylogenetic Trees

• Classification lists the unique characters of
  each taxon and is intended to reflect phylogeny
• Primitive characters
• Present in all members of a group, and
• Present in the common ancestor
• Derived characters
• Present in some members of a group, but
• Absent in the common ancestor

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Cladistic Systematics

• Traces evolutionary history of the group under
  study
• Uses shared derived characters to
• Classify organisms, and
• Arrange taxa into a cladogram
• A cladogram is a special type of phylogenetic
  tree
• A clade is an evolutionary branch that includes
• A common ancestor, together with
• All its descendent species

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Cladistics
Ideally, classification is based on establishing
the evolutionary relationships between organisms.
The evolutionary relationship between organisms
is their phylogeny.
Cladistics is the method of classification based
on establishing phylogenies (i.e. getting at
evolutionary relationships.
Cladistics proceeds by comparing shared ancestral
and shared derived characters between sets of
organisms.
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Cladistics
The greater the number of derived characters
shared by a pair of organisms, the closer their
degree of relationship.
The closer the degree of relationship, the closer
the most recent common ancestor.
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Constructing a Cladogram
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Parsimony (KISS)

• Cladists are always guided by the principle of
  parsimony
• The arrangement requiring the fewest assumptions
  is preferred
• This would
• Leave the fewest number of shared derived
  characters unexplained
• Minimize the number of assumed evolutionary
  changes
• The reliability of a cladogram is dependent on
  the knowledge and skill of the investigator

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Alternate, Simplified Cladograms
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• Cladistic analysis is often a search for the
  simplest hypotheses about phylogeny

• Phylogenetic tree according to cladistic analysis

Lizards
Snakes
Crocodiles
Birds

• Phylogenetic tree according to classical
  systematics

Lizards
Snakes
Crocodiles
Birds
Figure 15.13B, C
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Cladistic Versus Traditional View ofReptilian
Phylogeny
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Results of Cladistic Analyses Sometimes Run
Counter to Classical Classification Schemes
Which pair is more closely related? A
lizard/crocodile or bird/crocodile?
Cladistic analysis indicates that the
bird/crocodile pair is more closely related.
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• Taxonomists often debate the particular placement
  of organisms in categories as they strive to make
  their categories reflect evolutionary
  relationships.
• Because classification reflects evolutionary
  relationships, the same evidence for
  classification is used.
• Fossil records
• Homologous structures
• Vestigial organs
• Embryological development
• Biochemical comparisons
• Biogeography

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Its Critical (and often difficult) To
Distinguish Homology from Analogy
Homologous structures, like the bat wing and
gorilla arm, are similar because they are derived
by modification of a shared ancestral structure.
Homology is the key to establishing
phylogenies.
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Distinguishing Homology from Analogy
Analogy is similarity due to convergent evolution.
Analogy mistaken for homology confuses
phylogenies.
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Another Set of Analogies Created by Convergent
Evolution
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• A phylogenetic tree based on molecular data

Polarbear
Asiaticblack bear
Americanblack bear
Giantpanda
Spectacledbear
Brown bear
Sunbear
Slothbear
Lesserpanda
Raccoon
Pleistocene
Pliocene
Miocene
Ursidae
Procyonidae
Oligocene
Common ancestralcarnivorans
Figure 15.12A
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Classification Systems

• Until the middle of the twentieth century,
  biologists recognized only two kingdoms
• Plantae (plants) and Animalia (animals)
• Protista (protists) were added as third kingdom
  in the 1880s
• Whittaker expanded to five kingdoms in 1969 by
  adding Fungi and Monera
• Woese Kandler Wheelis expanded the five
  kingdoms to six in 1977 by dividing Monera into
  Eubacteria and Archaebacteria
• Woese, Kandler Whellis separated the kingdoms
  into domains based on cell structure in 1990.
• Currently, there is a push to separate the
  kindgom Protista into 3 new kingdoms for a total
  of eight!

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Summary of the History
Linnaeus17352 kingdoms Haeckel186613 kingdoms Chatton193752 empires Copeland195664 kingdoms Whittaker196925 kingdoms Woese et al.197776 kingdoms Woese et al.199033 domains
(not treated) Protista Prokaryota Monera Monera Eubacteria Bacteria
(not treated) Protista Prokaryota Monera Monera Archaebacteria Archaea
(not treated) Protista Plantae Protista Protista Protista Eukarya
Vegetabilia Plantae Plantae Protista Fungi Fungi Eukarya
Vegetabilia Plantae Plantae Plantae Plantae Plantae Eukarya
Animalia Animalia Plantae Animalia Animalia Animalia Eukarya
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Domains determined by cell type

• The current system recognizes two basically
  distinctive groups of prokaryotes

• The domain Bacteria
• The domain Archaea
• A third domain, the Eukarya, includes all
  kingdoms of eukaryotes

BACTERIA
ARCHAEA
EUKARYA
Earliestorganisms
Figure 15.14B
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Three-Domain System

• The Bacteria and Archaea are so different they
  have been assigned to separate domains
• Similar in that both are asexually reproducing
  unicellular prokaryotes
• Distinguishable by
• Difference in rRNA base sequences
• Plasma membrane chemistry
• Cell wall chemistry

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Three-Domain System

• Domain Eukarya
• Unicellular and multicellular organisms
• Cells with a membrane-bounded nucleus
• Sexual reproduction common
• Contains four kingdoms
• Kingdom Protista
• Kingdom Fungi
• Kingdom Plantae
• Kingdom Animalia

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6 Kingdoms of Life

• Single Celled - prokaryotes
• Archaea (extremophiles)
• Eubacteria (germs blue-green algae)
• Single Celled or Multicelled eukaryotes
• Protista (one-celled eukaryotes)
• Multicellular - eukaryotes
• Fungi
• Plantae
• Animalia

Prokaryote - small cell with no nucleus Eukaryote
- large cell will nucleus
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Figure 20.14
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Extremophiles (Archea)
Thermophiles
Halophiles
Cryophiles
Methanogens
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Eubacteria
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Protista
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Fungi
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Plantae
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Animalia