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Ch. 18
Part 3
Classification and Biodiversity
Classification
• System for biologists to arrange organisms into groups
• Categories = easier to remember
• Taxonomy
– Study and practice of classification
• Involves placing organisms into a series of taxonomic units called TAXA which form a hierarchy
• Each different organism is assigned a SPECIES
– Similar species are grouped into the same GENUS
» Similar GENERA (plural) are grouped into FAMILIES
• Similar families are grouped into ORDERS
• Similar orders are grouped into CLASSES
• Similar classes are grouped into PHYLUMS
• Similar phylum are grouped into KINGDOMS
Largest hierarchy of classification is
DOMAIN
So how do we classify???
Domain - Eukarya
Domains
• Broadest category of classification
• 1970’s
• Scientists needed a new category to distinguish between
extremophiles and normal bacteria
• Three main domains
– Domain Archaea:
• unicellular prokaryotes that live in extreme environments (very hot or very
cold, extremely acidic or basic)
• Extremeophiles
– Domain Bacteria: All other unicellular prokaryotes
– Domain Eukarya: Organism made up of eukaryotic Cells
• Includes 4 kingdoms: Protists, Fungi, Plants, Animals (and Monera)
Still some confusion
among scientists
over this one…
Domain Archaea
• Extremophiles
– Currently, there are some living in less extreme areas of the
ocean
• Prokaryotic
• More in common with Domain Eukarya than
– Genes coding for ribosomes very similar to those genes
found in eukaryotes Domain Bacteria
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No nucleus
Size similar to bacteria
No membrane-bound organelles
DNA is circular chromosome WITH histones present
Contain Plasmids
70S ribosomes
– Smaller than eukaryotes 80S ribosomes, BUT similar
structure to eukaryotic ribosomes
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Cell wall ALWAYS present (not made of peptidoglycan)
Divides by BINARY FISSION
Exist as single cells or groups of cells
Similar metabolism to normal bacteria
Transcription similar to eukaryotic transcription
Consists of 1 MAJOR
Kingdom
• Archaeabacteria
Domain Bacteria
• Prokaryotic (no nucleus)
• Small size 0.5 to 5 um in diameter
– Range between largest virus and
smalled eukaryote
• DNA is circular chromosome with NO
histones
• Plasmids present
• No membrane-bound organelles
present
• 70S ribosomes
• Cell wall always present
– Contains peptidoglycan NOT cellulose
• Divides by binary fission
• Exists as single cell or groups of cells
Consists of 1 MAJOR
Kingdom
• Eubacteria
Domain Eukarya
• Cells contain a nucleus
• Membrane-bound organelles
• DNA arranged in LINEAR
chromosomes WITH histones
• 80S ribosomes
– Mitochondria and chloroplasts
70S ribosomes
• Chloroplast and mitochondrial
DNA is circular
• Great Diversity in how they exist
– Unicellular
– Colonial
– multicellular
• Cell division by MITOSIS
• Asexual and Sexual reproduction
Consists of 4 MAJOR Kingdoms
• Protoctista
• Fungi
• Plantae
• Animalia
Kingdom Protoctista
• Any eukaryote that is not fungi, plant, or animal
• Consists of wide range of organisms
– PROTOZOANS (simple animals)
• Similar to animal cells
• NO cell wall
– ALGAE (seaweeds)
• Similar to plant cells
• Have cell wall and chloroplasts
• Strong argument to classify these as PLANTS
• Single-celled
• Exists as single cell or group of cells
Kingdom Fungi
• All heterotrophic
– Use organic compounds made by other
organisms for energy source
• Decomposers  energy obtained from dead and
decaying organism
• Parasitic  feed on host
• Confused with plants b/c they are NONMOTILE
• Wide range in size (some microscopic)
• Eukaryotic
• NO chlorophyll and do NOT use photosynthesis
• Reproduce by SPORES
• Simple body forms
– Unicellular
– HYPHAE  long threads with or without cross
walls
• Compacted hypahe make up larger body forms like
mushrooms
• Contain cell walls made of CHITIN
• NO cilia or flagella
Kingdom Plantae
• ALL multicellular
– Differentiated tissues and organs
• ALL photosynthetic
(AUTOTROPHIC)
• Eukaryotic (nucleus)
• Complex bodies
– Above ground
– Branched
• Few types of specialized cells
• SOME cells have chloroplasts and
use photosynthesis
• Cells contain LARGE, permanent
vacuoles for SUPPORT
• Cell walls made of CELLULOSE
May have flagella
– Male gametes in some types of
ferns
Kingdom Animalia
• Eukaryotic (nucleus)
• ALWAYS MULTICELLULAR
– Differentiated and specialized cells
• Differentiated into tissues and organs
• ALL Heterotrophic
• Contain NERVOUS SYTSEM
– Important in communication
• Do NOT have chloroplasts and
cannot use photosynthesis
– Exception: some coral polyps with
protoctists living in tissues
• Small, temporary cell vacuoles
(exocytotic vacuoles, food
vacuoles, lysosomes)NO cell walls
• Cells sometimes have cilia and
flagella
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Microorganisms
Range in size from 20-300 nm (50x
smaller than average bacteria)
Visible with electron microscope
NO cell structure
– No membrane
– No cytoplasm
– No ribosomes
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Consist solely of:
– Self-replicating DNA or RNA molecule
– Protective coat of proteins
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Capsid  protein coat
Capsomere  proteins embedded in
capsid
When free in environment:
– They are infectious
– No metabolism
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Must use machinery of host cells to
copy their genetic material
Use energy from host cell to do these
things
Taxonomic classification
– Based on diseases that viruses cause
– Type of genetic material they contain
Viruses
Types of Viruses
Nucleic
Acid
DNA
Number
of
Strands
1
2
Example
Host
Disease
Canine parvirus type
2
Dogs
Canine
parvovirus
African mosaic virus
Cassava plants
Mosaic virus
Varicella zoster virus
(VZV)
Humans
Chicken pox
Rotavirus
Humans
Gastroenteritis
Morbillivirus
Humans
Measles
Tombaco mosaic
virus (TMV)
Tomato,
tobacco,
pepper
Mosaic disease
Humans
HIV/AIDS
1
RNA
2