18.1 finding order in diversity. to study the diversity of life, biologists use a classification...
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18.1 Finding Order in Diversity
Classification
Why Classify?To study the
diversity of life, biologists use a classification system to name organisms and group them in a logical manner.Taxonomy
Assigning Scientific NamesCommon names can be
confusing and vary between regions.
Scientists agreed to use Latin and Greek when assigning scientific names to organisms.
This practice is still followed today as new organisms are discovered.
Binomial NomenclatureTwo-word
naming system used in differentiating a speciesGenus species
A genus is a group of related species.Ursus arctosUrsus
maritimus
Linnaeus's System of ClassificationIncludes seven levels- from smallest to
largestSpecies, Genus, Family, Order, Class, Phylum,
KingdomEach level is called a taxon.
FamilyGenera that share
many characteristics
UrsidaeUrsidae Ursus
arctosUrsidae Ursus
maritimusUrsidae
Ailuropoda melanoleuca
Linnaeus's System of Classification
OrderBroad taxanomic
category composed of similar families
CarnivoraExamples:
CanidaeFelidaeUrsidae
Linnaeus's System of Classification
ClassComposed of
similar orders
MammaliaIncludes
animals that are warm blooded, have body hair, and produce milk for their young.
Linnaeus's System of Classification
PhylumIncludes many
different organisms that share important characteristics
ChordataMammaliaAvesReptiliaAmphibiaSeveral classes of
fish
Linnaeus's System of Classification
Linnaeus's System of Classification
KingdomLargest and most
inclusive level Linnaeus started
with only 2- Animals & Plants
Now, we recognize 6! Plants, Animals,
Protists, Fungi, Archaebacteria, Eubacteria.
18.2 Modern Evolutionary Classification
Classification
Which Similarities Are Most Important?
Organisms determine who belongs in their species by choosing whom they mate with!
Scientists have “invented” larger taxa according to an organisms characteristics.
Evolutionary ClassificationStrategy of
grouping organisms together based on their evolutionary history
Phylogeny- evolutionary relationships among organisms
See Figure 18-7
Evolutionary Classification
Organisms that appear very similar may NOT, in fact, share a common ancestor.
Because… natural selection operating on species in similar ecological environments has often caused convergent evolution.
Classification Using Cladograms
Only identifies and considers characteristics of organisms that are evolutionary innovationsNew characteristics
that arise as lineages evolve over time
Derived Characters- appear in recent parts of a lineage but not in its older members.Can be used to
construct a cladogram
CladogramsDiagram that
shows the evolutionary relationships among a group of organisms
Useful for helping scientists understand how one lineage branched from another in the course of evolution
Like a “Family Tree”
Similarities in DNA & RNAAll organisms have
DNA to pass on to future generations.
The genes of many organisms show important similarities at the molecular level.
Similarities in DNA can be used to help determine classification.
Molecular ClocksComparison of DNA can be used to mark the passage
the time that two species have been separated on the “family tree”
The degree to which genes are dissimilar indicates how far in the past the two species shared a common ancestor.
18.3 Kingdoms & Domains
Classification
The Tree of Life EvolvesAll science adapts to new discoveries.In the early days of classification Linnaeus
proposed a 2-kingdom system.Today, because of new discoveries, we
recognize a six-kingdom system of classification.
Changing Number of Kingdoms
Timeline Names of Kingdoms
1700s Plantae Animalia
Late 1800s
Protista Plantae Animalia
1950s Monera Protista
Fungi Plantae
Animalia
1990s Eubacteria
Archeabacteria
Protista
Fungi Plantae
Animalia
The Three-Domain SystemMolecular clock model analysis has given rise
to a new taxonomic category larger than the kingdoms.Domains
Classification of Living ThingsDOMAIN Bacteria Archaea Eukarya
KINGDOM Eubacteria Archaebacteria
Protista Fungi Plantae Animalia
CELL TYPE Prokaryote Prokaryote Eukaryote Eukaryote Eukaryote Eukaryote
CELL STRUCTURE
S
Cell walls with
peptidoglycan
Cell walls without
peptidoglycan
Cell walls some with cellulose
Cell walls of chitin
Cell walls of
cellulose; chloroplast
s
No cell walls or
chloroplasts
NUMBER OF CELLS
Unicellular Unicellular Most Unicellular
Most Multicellula
r
Multicellular
Multicellular
MODE OF NUTRITION
Autotroph or
Heterotroph
Autotroph or Heterotroph
Autotroph or
Heterotroph
Heterotroph
Autotroph Heterotroph
Domain BacteriaUnicellularProkaryoticThick, rigid cell
walls Have
peptidoglycanCorresponds with
the kingdom EubacteriaEcologically
diverseSome need oxygenSome
photosynthesizeSome are free-
living Some are
parasites
Domain ArchaeaUnicellularProkaryoticCell walls
No peptidoglycan
Unique lipids Extremophiles
Hot springsBrine poolsAnaerobic mud
Domain EukaryaKingdom Protista
Cannot be classified as animals, plants or fungi
Most diverse kingdom
Most unicellularExcept multicellular
algae Autotrophs or
HeterotrophsSome share
characteristics with plants, some with fungi and some with animals.
Domain EukaryaKingdom Fungi
HeterotrophsFeed on
decaying organic matter
Secrete a digestive enzyme and absorb their food
MulticellularMushrooms
UnicellularYeast
Domain EukaryaKingdom Plantae
MulticellularPhotosynthetic
autotrophsNonmotileCell walls with
celluloseIncludes mosses,
ferns, cone-bearing and flowering plants
Domain EukaryaKingdom
AnimaliaMulticellularHeterotrophicNo cell wallsVery diverse
group