Transcript Chapter 18 - SCA Moodle

Chapter 18
Classification
18 – 1 Finding Order
in Diversity
• Evolution has lead to a staggering
variety or organisms
• Biologists have identified and
named about 1.5 million species
so far
• They estimate anywhere between
2 and 100 million additional
species have yet to be discovered
Taxonomy
• The science of classifying and
naming organisms
Assigning Scientific Names
• By the 18th century, European
scientists recognized that
referring to organisms by
common names was confusing
• Common names vary among
regions within a country
Mountain Lion
Cougar
Puma
Panther
Early Efforts at Naming
Organisms
• First attempts at standard scientific names
often described physical characteristics
• As a result, these names could be 20
words long!
• Ex.) The English translation of the
scientific name of a particular tree might
be “Oak with deeply divided leaves that
have no hairs on their undersides and no
teeth around their edges.”
Binomial Nomenclature
• Carolus Linnaeus (18th Century)
• Swedish Botanist
• Developed a system for naming
organisms
Binomial Nomenclature
• Two word naming system
Rules for Binomial
Nomenclature
• Written in italics
• First word is capitalized
• Second word is lowercased
Ex.)
Genus species
Genus species
G. species
• The name often tells you something
about the species
• Ex.) Tyranosaurus Rex
• Tyrant Lizard King
Taxon (taxonomic category)
• A group or level of organization
Linnaeus’s system of classification
uses seven taxonomic categories
Kingdom
Phylum
Class
Order
Family
Genus
species
Largest / Least
Specific
Smallest /
Most Specific
Mnemonic Device
Kingdom
Phylum
Class
Order
Family
Genus
species
•
•
•
•
•
•
•
King
Phillip
Came
Over
For
Good
Soup
18 -2 Modern Evolutionary
Classification
Problems with Traditional Classification
• Sometimes, due to convergent
Evolution organisms that are quite
different from each other evolve
similar body structures
• Ex.) Crab, limpet, barnacle
Evolutionary Classification
• Darwin’s theory of evolution
changed the entire way that
biologists thought about
classification
• Biologists now group organisms
into categories that represent
lines of evolutionary descent, not
just physical similarities
Classification Using Cladograms
• Many biologists now prefer a
method called cladistic analysis
• This method of classification
identifies and considers only
those characteristics that arise as
lineages evolve over time
Derived characteristics
• Characteristics that appear in
recent parts of a lineage but not in
its older members
Cladograms
• Diagram that shows the
evolutionary relationships among
a group of organisms
Similarities in DNA and RNA
• Suppose you were trying to compare
diverse organisms such as yeast and
humans
• It wouldn’t make sense to try to classify
anatomical similarities
• The genes of many organisms show
important similarities at the molecular level
• These similarities can be used as criteria
to help determine classification
• Ex.) Myosin in humans & yeast
Molecular Clocks
• Use DNA comparison to estimate
the length of time that two species
have been evolving independently
Molecular Clocks
• Mutations happen all the time at
about the same rate
• A comparison of DNA sequences in
two species can reveal how dissimilar
the genes are
• The degree of dissimilarity is an
indication of how long ago the two
species shared a common ancestor
18 -3 Kingdoms and
Domains
• In taxonomy, as in all areas of
science, ideas and models change as
new information arises, some
explanations have been discarded
altogether, whereas others such as
Darwin’s theory of evolution by natural
selection, have been upheld
• So it should not be surprising that
since the 1800’s, the tree of life has
been revised and edited since the
discovery of all this new information
The Tree of Life Evolves
• Before Linnaeus’s time, the only
two Kingdoms that existed were
Plants and Animals
• As scientists discovered new
organisms that didn’t fit into the
plant or animal category, they
made a new category
The Old 5 Kingdom System
1.
2.
3.
4.
5.
Animals
Plants
Protist
Fungi
Bacteria-Monera
• In recent years, as evidence
about microorganisms continued
to accumulate, biologists come to
recognize that the Monera were
composed of two distinct groups
The New 6 Kingdom System
1.
2.
3.
4.
5.
6.
Animals
Plants
Protist
Fungi
Eubacteria
Archaebacteria
The Three Domain System
• Molecular analysis has given rise
to a new taxonomic category that
is now recognized by many
scientists
Domain
• Larger than a kingdom
3 Domains
1. Bacteria
• Eubacteria
2. Archaea
• Archaebacteria
3. Eukarya
• Protists, fungi, plants, animals
(Everything with a nucleus)
Domain Bacteria
• Unicellular
• Prokaryotic - no nucleus, no membrane
bound organelles
• Thick walls (containing peptigoglycan)
• Free living and parasitic
• Important decomposers
• Some photosynthesize
• Some don’t need oxygen
– Anaerobic
• Some need oxygen
– Aerobic
Agar
Bacteria
Colonies
Petri dish
What is this
used for?
Domain Archaea
• Unicellular
• Small
• Prokaryotic
• Live in extreme environments
Ex.) volcanic hotsprings, brine
pools, black organic mud without
oxygen
• Acidophiles – live in acidic
environments
• Thermophiles – can tolerate hot
temperatures 50 – 110 degrees
• Halophiles – can stand extreme
concentrations of NaCl
• Methanogens – Produce methane
CO2 + H  CH4
Acidophiles
Thermophile
Halophile
Domain Eukarya
• Consists of all organisms that
have a nucleus
Protista
• Small
• Mostly unicellular
• Eukaryotic – has a nucleus, and
membrane bound organelles
• Cannot be classified as animals,
plants or fungi, but share many
characteristics with plants,
animals and fungi
Plant like Protists
• Algae
• Photosynthetic – can make their
own food
Euglenas
Flagella
Diatoms
Dinoflagellates
Dinoflagellates
• Red tide
Green Algae
Red Algae
Brown Algae
Animal like Protists
• Protozoans
• Heterotrophic – can’t make their
own food
Fungus like Protists
• Slime molds, water molds
• Decompose their food
Fungi
• Mostly multicellular
Ex.) Mushroom, yeast
• Cell walls
Fungi
• Heterotrophs
• Feed on decaying organic matter
• Secrete digestive enzymes into
food source then
• Spread and reproduce by spores
Spores
• Reproductive cells that form new
organisms without fertilization
Many are used in medicine
• Antibiotics
• Anti rejection
• Anti viral
Penicillium
Plantae
• Multicellular
• Photosynthetic autotrophs – make
their own food by photosynthesis
• Non-motile
• Cell walls (cellulose)
Animalia
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•
•
•
•
Multicellular
Heterotrophic
No cell walls
Most move
Incredible diversity