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Biological Classification- How Many Species
Exist?
 Biodiversity is the variety within and among living
species.
 Number of species known to science is between
1.4 and 1.8 million
 Uncertainty due to differences in methods of storing
and describing specimens
 Total number of species – estimates range from
3 – 100 million
 Average estimate is ~10 million species on Earth
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Biological Classification - How Many Species
Exist?
 Systematists are scientists who specialize in
describing and categorizing organisms.
 They work in the field of biological classification.
 Biological collections such as natural history
museums and herbaria store samples of the
different species.
 Systematists evaluate these collections to determine
overlap in identifying of species.
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Biological Classification - Kingdoms and
Domains
 Modern species are divided into three large groups,
or domains.
 Bacteria, Archaea, and Eukarya
 Within Eukarya, four kingdoms are also recognized
 Plantae
 Animalia
 Fungi
 Protista
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The tree of life.
Eukarya
Bacteria
Archaea
Protista
Plants Fungi Animals
Time
Present
time
More recent
divergence
Divergence early
in life’s history
4 billion
years ago
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Biological Classification - Kingdoms and Domains
[INSERT TABLE 13.2 ON THIS SLIDE]
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Biological Classification - A Closer Look:
Kingdoms and Domains
 Recently, some scientists have begun to suggest
that organisms should be classified based on
evolutionary relationships.
 Major groups under this system correspond to
divergences early in life’s history.
 Determining evolutionary relationships requires
comparing DNA.
 DNA of closely related organisms should be more
similar than DNA of distantly related organisms.
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Biological Classification - A Closer Look:
Kingdoms and Domains
 Using rRNA to determine relationships among
distantly related organisms
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Animation: The Tree of Life
Click “Go to Animation” / Click “Play”
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The Diversity of Life - Bacteria and Archaea
 Life on earth arose at least 3.6 million years ago,
according to the fossil record.
 Most ancient fossilized cells are very similar to modern
bacteria and archaea
 Prokaryotes like bacteria and archaea don’t have a
nucleus, lack mitochondria and chloroplasts, and most
are unicellular
 Incredibly numerous and diverse
 Found on every square centimeter of the earth’s surface,
even inside deep sea vents, far underground, and in
clouds
 Prokaryotes are called microbes and are studied by
microbiologists.
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 Domain Bacteria
 Most bacteria are probably harmless to humans.
 We are most familiar with the ones that cause disease
 Many known bacteria obtain nutrients by decomposing dead
organisms
 Competition between bacteria has produced compounds
that humans make use of.
 Antibiotics – ~50% of antibiotics are derived from
bacterial sources
 Restriction enzymes – proteins that chop DNA at specific
sequences; useful in biotechnology
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 Domain Archaea
 Superficially similar to bacteria
 Differ in structure of cell membranes
 Archaeans typically found in extreme environments
(high temperature, high pressure, high salt
concentration)
 Taq polymerase comes from an archaean,
Thermophilus aquaticus
 Archaeans are likely to be source of other
interesting biomolecules
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The Diversity of Life – Domain Eukarya
 Evolution of the Eukaryotes
 Protists are the simplest of the eukaryotes
 Oldest eukaryotic fossils are ~2 billion years old,
1.5 billion years later than the first prokaryotic cells
 Endosymbiotic theory explains the evolution of
eukaryotes and their specialized structures.
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Endosymbiotic Theory
The Diversity of Life – Evolution of Eukaryotes
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[INSERT FIGURE 13.8 ON THIS SLIDE]
The Diversity of Life – Protista

Modern protists contain members that resemble animals, plants, and fungi.
 Most members of the kingdom are not known
 Protists are eukaryotes that don’t belong in Kingdom Fungi, Kingdom Plantae
or Kingdom Animalia
 Protists can be heterotrophic or autotrophic
 Heterotrophic – protozoans
 Some of these can cause disease
 Autotrophic
 Multicellular – “seaweeds”
 Unicellular - phytoplankton
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The Diversity of Life – Protista
The Diversity of
Protists:
Ciliates,
flagellates,
amoebas, diatoms,
algae, slime molds
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The Diversity of Life – Protista
 Bioprospectors have examined the plant-like
protists most closely for useful compounds.
 Natural selection has driven the evolution of
defensive compounds in these organisms.
 Extracts from red algae might be used in anti-viral
medication.
 Carageenan, a stabilizer and thickener, also comes
from protists.
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(a) Animal-like protist
(b) Fungus-like protist
Mattesia oryzaephili is a parasite that infests and kills
beetles in stored grain. M. oryzaephili may be useful in
controlling these pests.
Lagenidium giganteum, sprayed on ponds to control
mosquito populations
(c) Plant-like protist
(d) Plant-like protist
Gonyaulax polyedra, a luminescent alga used to measure
levels of toxic materials in ocean sediments
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Chondrus crispus, a red alga that is the source of
carageenan
The Diversity of Life – Animalia
 Animals comprise a wide range of organisms, but
all share a common set of characteristics.
 Multicellular
 Heterotrophic (must eat to get energy)
 Mobile during at least one stage of life
 By 530 million years ago, all modern animal
groups were present.
 Most appeared quickly in fossil record
 Multicellular organisms quickly proliferated
 Known as Cambrian explosion
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The Diversity of Life – Animalia
A sampling
of animal
diversity
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13.2 The Diversity of Life – Animalia
A sampling
of animal
diversity
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The Diversity of Life – Animalia
 Most bioprospecting work focuses on invertebrates.
 Vertebrates only account for ~4% of animals
 Think about how many insects there are compared
to us; think about how many worms there are
compared to us
 Invertebrates are far more numerous and diverse
 Many invertebrates produce compounds found
nowhere else in nature
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The Diversity of Life – Animalia
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The Diversity of Life – Fungi
 Fungi characteristics
 Immobile
 Many reproduce by releasing spores
 Heterotrophic
 Feed by means of hyphae
 The hyphae of fungi can extend over a very large area
 DNA analysis by mycologists indicates fungi is more
closely related to animals than to plants
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The Diversity of Life – Fungi
 Fungi are grouped on the basis of spore formation
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The Diversity of Life – Fungi
 Commercially important fungal forms
 Yeast is a single celled type of fungi that is used in
bread, wine, and beer making.
 Mold is quickly reproducing and fast growing to
produce flavorful cheeses
 Fungi produce a number of important drugs
 Antibiotics
 Cyclosporin
 Statins
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The Diversity of Life – Plantae
 Characteristics of Plantae
 Multicellular
 Eukaryotic
 Autotrophic (manufacture own food) via
photosynthesis
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The Diversity of Life – Plantae
 Plants have been present on land for ~400 million
years.
 First plants were low to ground, lacked vascular
tissue
 Evolution of vascular tissue for water and nutrient
transport
 Allowed growth to tree size
 Allowed growth in drier areas
 Most modern plants in group only ~140 million
years old
 Flowering plants
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Diversity of flowering plants.
(a) Foxglove (Digitalis
purpurea)
(b) Aloe (Aloe barbadensis)
(c) Willow (Salix alba)
Source of heart drug digitalis
Source of aloe vera, used to treat burns and dry skin
Source of aspirin
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The Diversity of Life – Plantae
 Over 90% of modern plants are flowering plants
and many specializations
 Rapid increase of flower plant species is called
adaptive radiation.
 Flowering plants employ double fertilization method
or reproduction
 Also often involve animals in reproductive process
(pollination) – lots of coevolution has happened with
flowering plants and animals that eat them
 Also synthesize many secondary compounds that
deter predators
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The Diversity of Life – Plantae
 Kingdom Plantae is the source of many drugs
and compounds.
 Source of most naturally derived drugs
 Aspirin, Digitalis, Morphine, and Caffeine
 Pharmaceutical manufacturers reproduce
hundreds of compounds first found in plants
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The Diversity of Life - Viruses
A virus consists of a strand of DNA or RNA
 Viruses hijack
transcription machinery
of cells to reproduce
 Once hijacked cell
cannot perform own
functions
 HIV, smallpox, polio,
influenza are all caused
by viruses
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Figure 12.18
Animation: Endosymbiotic Theory
Click “Go to Animation” / Click “Play”
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Learning About Species - Fishing For Useful Species
The National Cancer Institute has employed
a brute-force approach to looking for anticancer compounds
 Receive specimens from around the world,
extract materials and screen against cancer
cell lines
 One major compound, Taxol, has been
identified using this technique
 Isolated from Pacific yew tree, a mitotic
inhibitor used as cancer medication
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http://en.wikipedia.org/wiki/Taxus_brevifolia
Learning About Species – Understanding Ecology
 Understanding an organism’s ecology—how it lives
in its environment—can be helpful in evaluating
potentially beneficial compounds.
 Survival in extreme environments
 High levels of competition with bacteria and fungi
 Susceptibility to predation
 Ability to live on or in other organisms
 Survival in high population densities
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Learning About Species – Reconstructing
Evolutionary History
 A classification system reflecting evolutionary
relationships is more useful to scientists.
 An organism’s chemical traits will probably be
similar to those of its closest relative
 If looking for new compounds, could begin by
screening close relatives of organisms already
known to produce compounds
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Learning About Species – Reconstructing
Evolutionary History
 The challenge in making an evolutionary
classification is that organisms do not always
resemble their closest living relatives.
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Learning About Species – Developing
Evolutionary Classifications
 An evolutionary classification of sparrows
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Learning About Species – Developing
Evolutionary Classifications
 Reconstructing evolutionary history not always as
easy as the sparrow example.
 Can be confounded by loss of traits, and
convergence
 DNA provides a means of testing evolutionary
hypotheses
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Learning About Species – Testing Evolutionary
Classifications
 Scientists can test evolutionary hypotheses with
data from fossils and from living organisms.
 Fossils provide information about the genealogy of
different living groups
 Comparison of DNA from living organisms can also
validate or refute proposed classifications
 DNA can give clues to near relatives, but lab process
can take time
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Learning About Species – Learning From the
Shamans
 Often local people in biologically diverse areas
make extensive use of naturally occurring products.
 Shamans often have much knowledge of locally
useful compounds.
 Biopiracy is when local knowledge is used without
benefiting local people.
 UN Convention on Biodiversity is supposed to
address this.
 Our biodiversity represents an enormous potential,
but only if we recognize its value.
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Overview of Classification
 Domain Bacteria – prokaryotic
 Bacteria we are familiar with
 Domain Archaea – prokaryotic
 Includes extremophile bacteria
 Domain Eukarya – eukaryotic
 Includes protists, fungi, plants, animals
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