Transcript Chapter 18: Classification

Chapter 18: Classification
Why Classify?
Biologists have identified and
named about 1.5 million species
and estimate that anywhere
between 2 and 100 million
additional species have yet to
be discovered.
To study the diversity of life, biologists use
a classification system to name organisms
and group them in a logical manner
(taxonomy).
• Referring to organisms by their common names can be
quite confusing. (ex: buzzard in UK = hawk, buzzard in
U.S. = vulture)
• Catfish, starfish, seahorse, jellyfish…. What are
they?
• A Swedish botanist named Carolus Linnaeus developed a
two-word naming system called binomial nomenclature.
Linnaeus’s System of Classification
Section 18.1 – Finding Order in Diversity
• Good classification does two things:
– Organized into groups that have biological similarities
– Organize according to unique/important
characteristics/how related
• Binomial Nomenclature (naming system)
• 2 part scientific name
• Genus species
– Italicize letters
– Genus Capitalized; species lowercase
• EX. Panthera pardus panther or leopard
(genus species) same species, different common name)
FYI: The genus Ursus contains 5 other kinds of bears, including polar
bears, black bears, and brown bears.
• The polar bear, for example has the scientific name Ursus maritimus.
• The second part of a scientific name – maritimus, is unique to each
species within the genus.
• Often, this part of the name is a Latinized description of
some important trait or an indication of where it lives.
• For example, the Latin word maritimus
refers to the sea, where polar bears live.
• Another example – humans: Homo sapiens
Frogs & Toads of Illinois FYI
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American toad (Bufo americanus)
Blanchard’s cricket frog (Acris crepitans blanchardi)
Bullfrog (Rana catesbeiana)
Cope’s gray treefrog (Hyla chrysoscelis)
Crawfish frog (Rana areolata)
Eastern gray treefrog (Hyla versicolor)
Eastern spadefoot (Scaphiopus holbrooki)
Fowler’s toad (Bufo fowleri)
Green frog (Rana clamitans)
Northern leopard frog (Rana pipiens)
Pickerel frog (Rana palustris)
Plains leopard frog (Rana blairi)
Southern leopard frog (Rana sphenocephala)
Spring peeper (Hyla crucifer)
Western chorus frog (Pseudacris triseriata)
Wood frog (Rana sylvatica)
Section 18.2 – Modern Evolutionary Classification
• Traditional classification system is that scientists
relied on body structure comparison
• Organisms that are quite different from each other
evolve similar body structures.
• Ex: crabs, barnacles, and limpets
Traditional Classification vs. Evolutionary Classification
Appendages
Crab
Conical Shells
Barnacle
Limpet
Crustaceans
Crab
Gastropod
Barnacle
Limpet
Molted
exoskeleton
Segmentation
Tiny free-swimming larva
CLASSIFICATION
BASED ON VISIBLE
SIMILARITIES
CLADOGRAM
Evolutionary Classification
• Darwin’s ideas about descent with modification
have given rise to the study of phylogeny, or
evolutionary relationships among organisms.
Used today.
Classification Using Cladograms
• To refine the process of evolutionary classification,
many biologists now use a method called cladistic
analysis.
• Uses derived characters – unique characteristics that
appear in recent organisms.
Cladograms
• Derived characters can be used to construct a
cladogram, a diagram that shows the evolutionary
relationships among a group of organisms.
Cladogram of Animal Kingdom
Echinoderms
Arthropods
Annelids
Mollusks
Radial
Symmetry
Roundworms
Flatworms
Pseudocoelom
Cnidarians
Radial
Symmetry
Protostome Development
Three Germ Layers;
Bilateral Symmetry
Sponges
Tissues
Multicellularity
Single-celled
ancestor
Deuterostome
Development
Coelom
Chordates
Similarities in DNA & RNA
• The genes of many organisms show
important similarities at the molecular
level. These similarities are used to
classify.
• EX. Humans and yeast both have a gene that codes for
myosin (a protein in our muscles) — an indicator that
humans and yeast have a common ancestor.
DNA Evidence Example
• In the traditional classification system, African vultures and
American vultures were classified together, but DNA analysis
has revealed that American vultures are actually more closely
related to storks.
• Based on DNA analysis, we know
that chimpanzees are our closest
living relatives (humans and
chimps share 98.5% same DNA).
Molecular Clocks
• Comparisons of DNA can show how closely
related organisms are.
• A model known as a molecular clock uses DNA
comparisons to estimate the length of time that
two species have been evolving independently.
• Neutral mutations (those that have no effect on phenotype)
accumulate in the DNA of different species.
• The more similar the neutral DNA (genes) the more closely
related the organisms.
18-3 Kingdoms and Domains
The Tree of Life evolves
• Linnaeus’s 2-kingdom classification was
eventually revised to include 6 kingdoms:
Eubacteria, Archaebacteria, Protista, Fungi,
Plantae, and Animalia
The Three Domain System
• Molecular analyses have given rise to a new
taxonomic category called the Domain
• Domain- a more inclusive category than any other—
larger than a kingdom
1. Bacteria- corresponds to the kingdom Eubacteria
2. Archaea- corresponds to the kingdom
Archaebacteria
3. Eukarya- corresponds to the kingdoms protists,
fungi, plants, and animals
Domain Bacteria
– Unicellular and prokaryotic
– Thick, rigid cell walls with peptidoglycan (gram +)
– Ecologically diverse (some are free-living while
others are parasites, some need oxygen while
others are killed by it)
– Autotrophic or heterotrophic
• EX. Streptococcus, E. coli, Syphilis, Chlamydia,
etc.
Domain Archaea “ancient bacteria”
• Unicellular and prokaryotic
• Live in extreme environments (volcanic hot
springs, black organic mud deprived of oxygen,
and brine pools)
• Cell walls lack peptidoglycan and cell
membranes contain unusual lipids not found in
any other organism (gram -)
• Autotrophic or heterotrophic
• EX. Methanogen, halophiles
Domain Eukarya
• Consist of all organisms with a nucleus and is organized into
the 4 remaining kingdoms
1. Protista
• “taxonomic misfits” Don’t fit into other categories.
• Most single-celled; some colonial, microscopic ¼ inch.
Neither plant nor animal.
• Some photosynthetic; others heterotrophic
• Most Diverse Group- Amoeba (some cause dysentery; others
harmless) paramecium, slimemolds (fungus-like), diatoms
(plant-like), giardia (animal-like parasite), other diseases
caused are sleeping sickness and malaria.
• Sexual and asexual reproduction
2. Fungi
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Produce foods such as
Cheese, soy sauce, mushrooms
Cell walls of chitin
Most multicellular; some
unicellular/ sexual and asexual reproduction
Heterotrophic—feed on dead organic matter (saprobes)
Fermentation to make alcohol
Produce antibiotics
Produce chemicals used in soaps and plastics
EX. mushrooms, yeast, potato blight, ringworm, mildew
3. Plantae
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Cell walls of cellulose, Contain chloroplasts, Multicellular,
Autotrophic, Nonmotile
Most are terrestrial and have adapted in the following ways:
– Control water loss
– Vascular tissue- move materials (Xylem-water and Phloem-food)
– Protective packaging for gametes and embryos (pollen, eggs, seeds)
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Ex: seed plants (angiosperms and gymnosperms)
seedless plants (mosses, ferns, horsetails)
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Animalia
Multicellular, Heterotrophic, lack cell walls
Great diversity and many species exist in nearly every part
of the planet. Phylums listed below for Kingdom Animalia:
Phylum Porifera – sponges
Phylum Cnidaria – hydras, jellyfish, sea anemone, corals
Phylum Platyhelminthes – flatworms (planaria, flukes,
tapeworms)
• Phylum Nematoda – roundworms (nematodes)
• Phylum Mollusca – mollusks (snails, squid, sea slugs, oyster)
• Phylum Annelida- segmented worms (earthworms, leeches,
marine)
• Phylum Arthropoda – Insects, crustaceans, spiders, mites,
millipedes, etc
• Phylum Echinodermata- sea stars, sea cucumbers, sand dollars,
brittle stars
• Phylum Chordata- chordates or “vertebrates” during all or part of
life (mammals, birds, reptiles, amphibians, fish, tunicates, etc.)
Key Characteristics of Kingdoms and Domains
Classification of Living Things
DOMAIN
KINGDOM
CELL TYPE
CELL
STRUCTURES
Bacteria
Archaea
Eubacteria
Archaebacteria
Prokaryote
Prokaryote
Cell walls with
peptidoglycan
Cell walls
without
peptidoglycan
NUMBER OF
CELLS
MODE OF
NUTRITION
EXAMPLES
Eukarya
Fungi
Protista
Eukaryote
Eukaryote
Cell walls of
chitin
Cell walls of
cellulose;
chloroplasts
Most
multicellular;
some
unicellular
Multicellular
Autotroph
Eukaryote
Cell walls of
cellulose in
some; some
have
chloroplasts
Unicellular
Unicellular
Autotroph or
heterotroph
Autotroph or
heterotroph
Autotroph or
heterotroph
Heterotroph
Streptococcus,
Escherichia coli
Methanogens,
halophiles
Amoeba,
Paramecium,
slime molds,
giant kelp
Mushrooms,
yeasts
Most unicellular;
some colonial;
some
multicellular
Plantae
Animalia
Eukaryote
No cell walls
or chloroplasts
Multicellular
Mosses, ferns,
flowering
plants
Heterotroph
Sponges,
worms,
insects, fishes,
mammals
Questions
1. How is a cladogram used?
2. How is a dichotomous key used?
3. How do you name organisms?