Classification of Organisms
Biology- Chapter 18 (508-533)
Modern Bio Chapter 17 (336-351)
Biology Concepts and Connections
Chap 15 (304-310)
Web cd 15c
18.1 Finding Order in Diversity
18.2 Modern Evolutionary Classification
18.3 Building the Tree of Life
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Objectives
• Relate biodiversity to biological
classification
• Explain why naturalist replaced Aristotle's
classification system
• Identify the main criterion that Linnaeus
used to classify organisms
• List the common levels of modern
classification from general to specific
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Biodiversity
• Biologists have named and classified
almost 2 million species. However, they
estimated that the total number of species
on Earth is much greater. Over time,
Scientist have created various systems of
classification to organize their knowledge
of the tremendous number of species.
Each system places species into
categories bases on particular
characteristics
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Classifying Organisms
• biodiversity- the variety of organisms
considered at all levels from populations to
ecosystems
• Continues to grow everyday  not complete
• Erwin cataloging insects, over 1000 beetles, 30
million species of insects ww
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Taxonomy
sciences of describing , naming, and
classifying organisms
• Taxon or taxa- group with in a taxonomic
system
• Aristotle, Greek philosopher, classified
organisms into only 2 taxa
1. animals-land, air, or water,
2. Plant- based on stems
As it progresses they realized it was not
working well
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Linnaean System
Carolus Linnaeus, Swedish naturalist (1707-1778)
• Developed a system of grouping
organisms into hierarchical categories
according to their form and structure
• Simple to complex, 7 categories
Domain, Kingdom, Phylum, Class, Order,
Family, Genus, Species
Did King Philip Come Over For Grape Soda
Can you do your own?
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Levels of Classification pg1079
1.
2.
3.
4.
5.
6.
7.
8.
Domains- prokaryotes or eukaryotes- Eukarya
Kingdom- animals or plants- Animalia
Phyla (animals) or divisions (plants) Chordata
Classes-Mammalia
Orders- Carnivora
Family- Felidae
Genus- Felis
Species (Felis catus, domestic cat)
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Binomial Nomenclature
• Linnaeus gave organisms a species name
or a scientific name that contained 2 parts
• Linnaeus grouped species according to
anatomical similarities and differences.
2 Parts:
1. genus: Homo
2. species identifier: sapiens
Species name is written in italics and the
genus name capitalized, tend to come
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Binomial Nomenclature
The polar bear, for example, is called Ursus maritimus.
• The first part of the name—Ursus—is the genus to which the
organism belongs. A genus is a group of similar species. The
genus Ursus contains five other species of bears, including
Ursus arctos, the brown bear or grizzly bear.
• The second part of a scientific name—maritimus for polar
bears—is unique to each species and is often a description of
the organism’s habitat or of an important trait. The Latin word
maritimus refers to the sea: polar bears often live on pack ice
that floats in the sea.
• The scientific name of the red maple is Acer rubrum.
• The genus Acer consists of all maple trees.
• The species rubrum describes
the18red
Chapter
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Problems With Traditional
Classification
–
For example, adult barnacles and limpets live attached to rocks
and have similar-looking shells.
– Adult crabs don’t look anything like barnacles and limpets.
– Based on these features, one would likely classify limpets and
barnacles together and crabs in a different group. However, that
would be wrong.
–
Modern classification schemes look beyond overall similarities
and differences and group organisms based on evolutionary
relationships.
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systematic
• More than 200 years ago, Linnaeus
grouped organisms according to
similarities that he could readily see.
Modern biologists consider not only visible
similarities but also similarities in embryos,
chromosomes, proteins, and DNA. In
systematic, the goal is to classify
organisms in terms of their natural
relationships.
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objectives
• Identify the kinds of evidence that modern
biologists use in classifying organisms
• Explain what information a phylogenetic
diagram displays
• State the criteria used in cladistic analysis
• Describe how a cladogram is made
• Explain cladistic taxonomy, and identify
one conclusion that is in conflict with
classical taxonomy
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Evolutionary Classification
What is the goal of evolutionary classification?
– The goal of phylogenetic systematics, or evolutionary
classification, is to group species into larger categories that reflect
lines of evolutionary descent, rather than overall similarities and
differences.
– The concept of descent with modification led to phylogeny—the
study of how living and extinct organisms are related to one
another.
–
Advances in phylogeny, in turn, led to phylogenetic systematics,
or evolutionary classification. Phylogenetic systematics groups
species into larger categories that reflect lines of evolutionary
descent, rather than overall similarities and differences.
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Phylogenetics
• The analysis of the evolutionary or
ancestral relationships among taxa
• Use phylogenetic diagram or tree
• They can change due to new discoveries
and investigations
• Determine if any evidence of shared
ancestry
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What is a Cladograms
– A clade is a group of species that includes a single common ancestor and
all descendants of that ancestor—living and extinct.
–
A clade must be a monophyletic group. A monophyletic group must
include all species that are descended from a common ancestor, and
cannot include any species that are not descended from that common
ancestor.
A cladogram links groups of organisms by showing how evolutionary lines,
or lineages, branched off from common ancestors.
– Modern evolutionary classification uses a method called cladistic analysis
to determine how clades are related to one another.
–
This information is used to link clades together into a cladogram, which
illustrates how groups of organisms are related to one another by showing
how evolutionary lines, or lineages, branched off from common ancestors.
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cladistic
• System of phylogenetic analysis that uses
shared and derived characters
• Shared character- is a feature that all members
of a group have in common, such as hair in
mammals or feathers in birds
• Derived character- feature that evolved only
within the group under consideration, feathers
evolved with in birds
• Clad- group of organisms that includes an
ancestor plus all of its descendants
• Cladogram- chart developed
•
Fig 17.3
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Building Cladograms
– This cladogram represents current
hypotheses about evolutionary relationships
among vertebrates.
– Note that in terms of ancestry, amphibians
are more closely related to mammals than
they are to ray-finned fish!
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Derived Characters
–
Whether or not a character is derived depends on the level at
which you’re grouping organisms. Four limbs, for example, is a
derived character for the clade tetrapoda. Hair is a derived
character for the clade Mammalia, but four limbs is not derived
for mammals. If it were, only mammals would have four limbs!
– Specialized shearing teeth is a derived character for the clade
Carnivora—of which both the coyote and lion are members.
Neither hair nor four limbs is a derived character for this clade.
– Retractable claws is a derived character for the clade Felidae
(the cats). Notice that lions have this trait, but coyotes do not.
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Reading Cladograms
– This cladogram shows a simplified
phylogeny of the cat family.
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Clades and Traditional
Taxonomic Groups
Two clades do include the birds: clade Aves, (the birds
themselves), and clade Reptilia. Therefore, according to
cladistics, a bird is a reptile!
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New Techniques Suggest
New Trees
– The use of DNA characters in cladistic analysis has
helped to make evolutionary trees more accurate.
– For example, traditionally African vultures and
American vultures were classified together in the
falcon family.
– Molecular analysis, however, showed that DNA from
American vultures is more similar to the DNA of storks
than it is to the DNA of African vultures.
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New Techniques Suggest
New Trees
–
Often, scientists use DNA evidence when anatomical traits
alone can’t provide clear answers.
–
For example, giant pandas and red pandas share many
characteristics with both bears and raccoons.
–
DNA analysis revealed that the giant panda shares a more
recent common ancestor with bears than with raccoons.
Therefore, the giant panda has been placed in a clade with
bears.
–
Red pandas, however, are in a clade with raccoons and other
animals like weasels and seals.
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THINK ABOUT IT
–
The process of identifying and naming all known organisms,
both living and extinct, is a huge first step toward the goal of
systematics.
–
The real challenge, however, is to group everything—from
bacteria to dinosaurs to blue whales—in a way that reflects their
evolutionary relationships.
–
Over the years, new information and new ways of studying
organisms have produced major changes in Linnaeus’s original
scheme for organizing living things.
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Modern Classification
• Biologist continue to develop taxomies to
organize life’s enormous diversity. They
regularly revise the many branches of the
“tree of life” to reflect current hypotheses
of the evolutionary relationships between
groups. They have revised the larges and
most fundamental categories of the
Linnean-inspired classification systemdomains and kingdoms.
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objectives
• Describe the evidence that prompted the
invention of the three-domain system of
classification
• List the characteristics that distinguish between
the domains Bacteria, Archaea, Eukarya
• Describe the 6-kingdom system of classification
• Identify problematic taxa in the 6-kingdome
system
• Explain why taxonomic systems continue to
change.
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Changing Ideas About
Kingdoms
–
During Linnaeus’s time, living things were classified as either
animals or as plants.
–
Animals were organisms that moved from place to place and used
food for energy.
–
Plants were green organisms that generally did not move and got
their energy from the sun.
–
As biologists learned more about the natural world, they realized
that Linnaeus’s two kingdoms—Animalia and Plantae—did not
reflect the full diversity of life.
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Changing Ideas About
Kingdoms
– Classification systems have changed
dramatically since Linnaeus’s time, and
hypotheses about relationships among
organisms are still changing today as new data
are gathered.
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1. Domains: Bacteria, Archaea, Eukarya
2. Kingdoms
a. Eubacteria
b. Archaebacteria
c. Protista
d. Fungi
e. Plantae
f. Animalia
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The Tree of All Life
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Domain Bacteria
–
Members of the domain Bacteria are unicellular and
prokaryotic. This domain corresponds to the kingdom
Eubacteria.
–
Their cells have thick, rigid walls that surround a cell
membrane and contain a substance known as
peptidoglycan.
–
These bacteria are ecologically diverse, ranging from freeliving soil organisms to deadly parasites. Some
photosynthesize, while others do not. Some need oxygen to
survive, while others are killed by oxygen.
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Domain Archaea
–
The domain Archaea corresponds to the kingdom
Archaebacteria.
–
Members of the domain Archaea are unicellular and
prokaryotic, and they live in some extreme environments—in
volcanic hot springs, brine pools, and black organic mud totally
devoid of oxygen. Many of these bacteria can survive only in
the absence of oxygen.
–
Their cell walls lack peptidoglycan, and their cell membranes
contain unusual lipids that are not found in any other organism.
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Domain Eukarya
– The domain Eukarya consists of all
organisms that have a nucleus. It comprises
the four remaining kingdoms of the sixkingdom system: “Protista,” Fungi, Plantae,
and Animalia.
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The “Protists”: Unicellular
Eukaryotes
–
The kingdom Protista has long been viewed by biologists as a
“catchall” group of eukaryotes that could not be classified as
fungi, plants, or animals.
–
Recent molecular studies and cladistic analyses have shown
that “the eukaryotes formerly known as “Protista” do not form a
single clade. Current cladistic analysis divides these organisms
into at least five clades.
–
Since these organisms cannot be properly placed into a single
taxon, we refer to them as “protists.”
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The “Protists”: Unicellular
Eukaryotes
– Most “protists” are unicellular, but one
group, the brown algae, is multicellular.
– Some “protists” are photosynthetic, while
others are heterotrophic.
– Some display characters that resemble
those of fungi, plants, or animals.
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Fungi
–
Members of the kingdom Fungi are heterotrophs with cell walls
containing chitin.
• Most fungi feed on dead or decaying organic matter. They secrete
digestive enzymes into their food source, which break the food
down into smaller molecules. The fungi then absorb these smaller
molecules into their bodies.
–
Mushrooms and other recognizable fungi are multicellular, like
the ghost fungus shown. Some fungi—yeasts, for example—are
unicellular.
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Plantae
–
Members of the kingdom Plantae are multicellular, have
cell walls that contain cellulose, and are autotrophic.
–
Autotrophic plants are able to carry on photosynthesis
using chlorophyll.
–
Plants are nonmotile—they cannot move from place to
place.
–
The entire plant kingdom is the sister group to the red
algae, which are “protists.” The plant kingdom, therefore,
includes the green algae along with mosses, ferns, conebearing plants, and flowering plants.
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Animalia
–
–
Members of the kingdom Animalia are multicellular and
heterotrophic.
Animal cells do not have cell walls.
–
Most animals can move about, at least for some part of
their life cycle.
–
There is incredible diversity within the animal kingdom, and
many species of animals exist in nearly every part of the
planet.
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