Transcript Document 7386518

The History of Organization
Aristotle 384-322 BC
Interested in biological classification.
Patterns in nature.
Carl Linnaeus
1707-1778 ACE
Father of
Biological
Classification!
Taxonomy:
How 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
The Linnaean
Hierarchical
Classification
System
Taxonomy: Assigning Names
• Rules
–
–
–
–
–
Latin
1st name capitalized
2nd name lower case
Italicized
Ex. Homo sapiens
Scientific Name
Kingdom
Phylum
Class
Order
Family
Genus
Species
Subspecies
Taxonomy:
Relationships
Kingdom
Phylum
Class
Order
Family
Genus
Species
Subspecies
Animalia
Chordata
Mammalia
Primates
Homididae
Homo
sapiens
sapiens
Animalia
Chordata
Osteichthyes
Salmoniformes
Salmonidae
Onchorhynchus
tshawytscha
Plantae
Pinophyta
Pinopsida
Pinales
Cupressaceae
Sequoia
sempervirens
Human
King Salmon
Coast Redwood
• Genera are grouped into progressively
larger categories
Table 15.10
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-rop`ter-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)
SPECIES
Evolution creates (and destroys) new species, but …
What is a species?
Its not as straightforward a question as most believe.
These are members of different species - eastern (left) and
western (right) meadowlark.
What is a Species?
And these are all members of a single species.
What is a Species?
The definition we’ll 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.
One Problem in the Biological Species Concept
For asexually-reproducing organisms, like these bacteria,
what constitutes a species?
How Many Species Are There?
We don’t 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).
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.
The Cretaceous/Tertiary Mass Extinction
Gary Larson
SYSTEMATICS AND
PHYLOGENETIC BIOLOGY
Systematists classify organisms by
phylogeny
• Reconstructing phylogeny is part of
systematics
– the study of biological
diversity and classification
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
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.
Figure 15.8
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
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
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.
Cladistics
A phylogeny
(cladogram) for
vertebrates.
each node
indicates a
common
ancestor
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.
Constructing a
Cladogram
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
Alternate, Simplified
Cladograms
• Cladistic analysis is often a search for the
simplest hypotheses about phylogeny
– Phylogenetic tree
according to
cladistic analysis
– Phylogenetic tree
according to
classical
systematics
Lizards
Lizards
Snakes
Snakes
Crocodiles
Crocodiles
Birds
Birds
Figure 15.13B, C
Cladistic Versus Traditional View of
Reptilian Phylogeny
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.
• 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
It’s 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.
Distinguishing Homology from Analogy
Analogy is similarity due to convergent evolution.
Analogy mistaken for homology confuses phylogenies.
Another Set of Analogies Created by Convergent Evolution
Ocotillo of the
US southwest
Allauidia of
Madagascar
• A phylogenetic tree based on molecular data
Brown bear
Polar
bear
Asiatic
black
bear
American
black
bear
Sun
bear
Sloth
bear
Spectacled Giant
panda
bear
Lesser
Raccoon panda
Miocene
Pleistocene
Pliocene
Oligocene
Ursidae
Procyonidae
Common ancestral
carnivorans
Figure 15.12A
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!
Summary of the History
Linnaeus
1735
2 kingdoms
Haeckel
1866[1]
3 kingdoms
Chatton
1937[5]
2 empires
Prokaryota
(not treated)
Copeland
1956[6]
4 kingdoms
Monera
Whittaker
1969[2]
5 kingdoms
Woese et al.
1977[7]
6 kingdoms
Woese et al.
1990[3]
3 domains
Eubacteria
Bacteria
Archaebacteria
Archaea
Monera
Protista
Protista
Protista
Fungi
Fungi
Protista
Vegetabilia
Animalia
Plantae
Animalia
Plantae
Eukarya
Plantae
Plantae
Animalia
Animalia
Plantae
Animalia
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
Earliest
organisms
Figure 15.14B
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
Three-Domain System
• Domain Eukarya
• Unicellular and multicellular organisms
• Cells with a membrane-bounded
nucleus
– Sexual reproduction common
– Contains four kingdoms
•
•
•
•
Kingdom
Kingdom
Kingdom
Kingdom
Protista
Fungi
Plantae
Animalia
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
Figure 20.14
Extremophiles (Archea)
Thermophiles
Halophiles
Cryophiles
Methanogens
Eubacteria
Protista
Fungi
Plantae
Animalia