Classification
Chapter 17
Why classify organisms?
currently there are 1.5 million known
species of living things
Taxonomy
field of science that deals with classifying
organisms according to their characteristics and
evolutionary history
Early Classification
Aristotle – 2000 BC
devised a classification system
• divided living things into 2 groups
PLANTS – divided into smaller groups based
on their stem structure – herbs, shrubs, trees
ANIMALS – divided into smaller groups based
on their habitat – land, air, water
Early Classification
Linnaeus - 1700’s - naturalist
• devised a classification
system based on
comparative morphology
• classification system had 7
taxonomic categories
(called TAXONS)
• devised a way to give
each organism a unique
2 word name
7 taxonomic categories
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Kingdom – largest group; most variety
Phylum/Division
Class
Order
Family
Genus
Species – smallest group; least variety
ACRONYM
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kingdom - KING
phylum - PHILLIP
class - CAME
order - OVER
family - FROM
genus - GREAT
species - SPAIN
American Crow
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Kingdom: Animalia
Phylum: Chordata (with backbones)
Class: Aves (birds)
Order: Passeriformes (songbirds)
Family: Corvidae (crows, jays)
Genus: Corvus
Species: brachyrhynchos
What do these animals
have in common?
Why classify bats and
birds together but not
include dragonflies?
Answer this….
Would a horse and a zebra belong to the
same species? Why or why not?
Might they be members of the same
genus? Why or why not?
Would a dog and a wolf belong to the
same species? Why or why not?
Might they be members of the same
genus? Why or why not?
Binomial Nomenclature
• giving an organism a 2 word name,
A SCIENTIFIC NAME
consists of two words
Genus – 1st word – capitalized
species – 2nd word – lower case
*written in latin
*underlined or italicized
Why Latin?
• “dead” language
– no changes being made
– it is not in use today
• is the basis for many of today’s languages
• assures a unique name for each species
Names may tell you…
• Name of geographic location
• Who discovered it
• The look of the organism
• Example:
– Linnea borealis
– Odocoileus virginianus
– Felis domesticus
Lasionycteris noctivagans
• nocti = nocturnal
• vagans = wanderer
• nyct = night
“wanderer at night”
Silver-haired bat
Dichotomous Key
“dividing into two parts”
• used to help identify an organism based
on it characteristics
• at each step in a dichotomous key you
have 2 choices
Species
• Typological: based on physical
characteristics (not used anymore)
• Biological: based on the ability to breed
and produce fertile offspring
• Phylogenetic: based on evolutionary
relationships (evolving from a common
ancestor)
MODERN CLASSIFICATION
Today, taxonomists
classify organisms in
such a way as to
indicate evolutionary
relationships.
Archaeopteryx – believed
to be the ancestor of birds
Modern Taxonomy
IS NOT BASED ON HABITAT!!!!
Today, taxonomists use…
• comparative morphology
• fossil evidence
• embryological evidence
• chromosomal evidence
• biochemical similarities
• physiological similarities
• evolutionary relationships
to determine the classification
of an organism
Other Changes…
sometimes, more than 7 categories
are needed….
SUBCATEGORIES CAN BE USED…
 subkingdom
 subphylum
 subclass
 suborder
 subfamily
 subgenus
 subspecies
DERIVED CHARACTERS
are used to help determine
evolutionary relationships
Derived Character - a feature (trait) that apparently evolved
only within a specific groups of organisms
such as - jaws, lungs, claws,
feathers, mammary glands,….
Ancestral Character – found with the entire line of descent
(including the ancestor)
Cladogram
diagram made by cladistic analysis that shows the
evolutionary relationships of organisms
2 Modern Systems of Classification
3 domain system
Domain archaea
Domain bacteria
Domain eukarya
6 kingdom system
Kingdom archaebacteria
Kingdom eubacteria
Kingdom protista
Kingdom fungi
Kingdom plantae
Kingdom animalia
Differences among Kingdoms
Archaebacteria and Eubacteria: prokaryotic,
unicellular
Protista: eukaryotic, unicellular and multicellular
Fungi: eukaryotic, cell wall of chitin, no
chloroplasts, unicellular and multicellular,
heterotrophic
Plantae: eukaryotic, cell wall of cellulose,
chloroplasts, all multicellular, autotrophic
Animalia: eukaryotic, no cell wall, all multicellular,
heterotrophic
Kingdoms
Archaebacteria and Eubacteria
(previously classified together as kingdom Monera)
Bacteria….
Eubacteria and Archaebacteria
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many are saprophytic (feed on dead organic matter)
many are parasitic (feed on living organic matter)
among the first forms of life
prokaryotic
ONLY KINGDOMS lacking
an organized nucleus and
membrane-bound organelles
Nostoc (cyanobacterium)
Methods of energy acquisition
• Chemosynthesis
• photosynthesis
• heterotrophic
Kingdom Archaebacteria
(“old bacteria”)
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prokaryotic
cell wall does not contain peptidoglycan
have unusual lipids in cell membrane
oldest and most primitive organisms known
life’s extremists - occupy environments that
“normal” organisms find too harsh
Archaebacteria….3 groups….
Methanogens - produce methane gas,
found in soil, swamps, digestive tracts of
animals
Extreme Halophiles – live in high salt
environments, found in salt lakes, Dead
Sea
Thermoacidophiles – live in hot, acidic
environments, found in volcanic vents,
hydrothermal vents
Kingdom Eubacteria
(“true bacteria”)
• cell wall contains peptidoglycan
• includes most of the bacteria that affects our
daily life including….
tetanus, strep throat, tooth decay,
E. coli, salmonella, botulism,
lyme disease, syphilis, and many more….
• some capable of chemosynthesis, some
photosynthesis, others are heterotrophic
Bacteria – Roles in Ecosystem
• can cause disease
• photosynthesis and oxygen production
– cyanobacteria (“blue-green bacteria”) contributed to
formation of atmospheric oxygen by photosynthesis
• food source
• nutrient transfer
– convert atmospheric N into forms useable forms for plants
and animals
• decomposition
– saprophytic (decompose dead tissue)
– symbiotic (live within a host organism)
• some oil deposits are attributed to cyanobacteria
Kingdom Protista
algae, protozoa, fungus-like protists
Protista
• Animal-like (protozoan), plant-like (algae) and
fungus-like protists
• heterotrophic and autotrophic
• eukaryotic
• freshwater, saltwater, soil
• because of great diversity,
classification is difficult
paramecium
Eukaryotes that are NOT fungi, animals, or plants!
Protista…. 3 groups….
Protozoa (“first animal”)
– “animal like”, single-celled, motile, heterotrophic
– digest food by engulfing, digesting, and absorbing it
Algae
– “plant like”, single-celled or colonial or multicellular
– diatoms, algae, dinoflagellates,…
Fungus Like Protists
- “fungus like”, includes slime molds and others
http://www.emc.maricopa.edu/faculty/farabee/BIOBK/BioBookDiversity_3.html
Protista – Roles in Ecosystem
• photosynthesis and oxygen production
• food source (algae)
– animal feed, fertilizers
– algae sheets used in some Japanese dishes
– additive to puddings, ice cream, salad dressing,
candy (carrageenan and alginate)
• can cause disease
– avian malaria, human malaria,
amoebic dysentery
Protista and Red Tides
http://www.redtide.whoi.edu/hab/rtphotos/noctiluca.jpg
• population
explosion of
dinoflagellates
• neurotoxin
released
• shellfish
concentrate toxin
• humans can be
killed by eating
shellfish
contaminated by
toxin
Kingdom Fungi
mushrooms, blights, rusts, molds, puffballs, morels,
yeasts, truffles, toadstools, shelf fungi,….
Fungi
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eukaryotic
made up of hyphae
mycelium=mass of hyphae
no roots, stems or leaves
no chlorophyll
saprophytic or parasitic
reproduce by spores
cell walls contain chitin
absorptive heterotrophs
multicellular and unicellular species
Roles in Ecosystem
• Food Source
– mushrooms, truffles, morels, cheeses,
bread, beer and wine
• Production of some Antibiotics
• Crop Parasites
– cause loss of food plants, spoilage,
infectious disease
• Dutch Elm Disease
• Chestnut Blight
• Benefit Wildlife
– food source, nest sites, hiding places
and cover
• Symbiosis - Mutualism
– lichens (fungus + alga)
– mycorrhizae (fungus and plant roots)
Kingdom Plantae
Plants
• eukaryotic, multicellular, photoautotrophs
• cell wall with cellulose
2 major groups of plants
nonvascular
and
vascular
Nonvascular Plants
• small (lack conducting cells)
• likely were the earliest land plants
• liverworts, hornworts and mosses
Vascular Plants
• have specialized cells for transporting materials
• Xylem (for transporting water and mineral nutrients)
• Phloem (for transporting sugars from leaves to the
rest of the plant)
• pines, cacti, grasses, trees, flowers, …..
Plants – Roles in Ecosystem
• food source
• generate oxygen
• provide habitat for humans and wildlife
American chestnut, late 1800s
Kingdom Animalia
•multicellular
•heterotrophic
•eukaryotic
•no cell wall
2 main groups
invertebrates and vertebrates
Invertebrates
(animals without a backbone)
sponges, jellyfish, corals, sea
anemones, scallops, oysters,
snails, octopi, squid, sea urchins,
sea stars, spiders, scorpions,
crabs, shrimp, insects, worms,
rotifers, comb jellies,…
Vertebrates
animals with a backbone (of bone or cartilage)
fish, amphibians, reptiles, birds, mammals
Let’s Review
This characteristic separates which kingdoms….
• All members are heterotropic?
• All members are autotrophic?
• Contains both heterotrophic and autotrophic members?
• All members prokaryotic?
• All members eukaryotic?
• Have chloroplasts?
• Have a cell wall?
• All members unicellular?
• All members multicellular?
• Contains both unicellular and multicellular members?