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Lecture 1: Chapter 20
Classification of Living Things
Professor: Dr. Barjis
Room:
P313
Phone:
(718)2605285
Email:
[email protected]
Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings
Alberts, Bray,
Sylvia S Mader
Hopkins,
Johnson
General Biology
Outline
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Taxonomy
– Binomial System
Species Identification
Classification Categories
Phylogenetic Trees
– Tracing Phylogeny
Cladistic Systematics
Phenetic Systematics
Classification Systems
Taxonomy (arrange” and “law )
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Taxonomy is the branch of biology dealing
with the naming, identification, and
classification of organisms.
Taxonomy uses a binomial system
developed by Linnaeus.
Taxonomy uses reproductive isolation as
the basis of definition of a species.
taxonomists use following categories of
classification: domain, kingdom, phylum,
class, order, family, genus and species
Living Organism
All living organisms are divided into 3 domains
Archae
Eukaryotes
Bacteria
Each Domain is divided into number of Kingdoms
Kingdom
Animalia
Kingdom
Plantae
Kingdom
Protista
Kingdom
Fungi
Each Kingdom is divided into number of Phylums e.g. Porifera , Cnidaria, Chordata……
Chordata
Animals with notochord, tail, nerve cord would fall into this phylum
Each Phylum is divided into number of Classes e.g. Mammalia, Amphibia, Reptilia……
Mammalia
Animals with mammary gland, hair/fur would fall into this class
Each Class is divided into number of Subclasses e.g. Monotremes , Placental mammals
Placental
Mammals that depend on placenta e.g. Carnivores (dogs), Primates ….
Each Subclass is divided into number of Orders e.g. Primates
Primates
Mammals that have enlarged brain, an opposable thumb.. e.g humans, gorilla
Each Order is divided into number of Families e.g. Hominidae, Apes…
Hominidae
Mammals that can stand erect would fall into this family
Each Family is divided into number of Genus e.g Homo
Homo
Mammals that walk upright on two legs
Each Genus is divided into number of Species
Sapience
Wise
Classifying Organisms
Binomial System
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In mid-eighteenth century, Linnaeus
developed the binomial system of naming
species.
– First word is genus.
– Second word (specific epithet) refers to
one species within genus.
 A species is designated by the full
binomial name (Genus species).
 Genus can be used to refer to group
of related species.
Species Identification
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Character traits are used to distinguish one
group from another are:
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structural features.
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chromosomal.
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molecular features.
A primitive character is one that is present in
the common ancestor and all members of a
group
Early biologists referred to animals as
‘‘simple’’ and ‘‘advanced,’’ but now it is more
accurate to use the terms: ‘‘primitive’’ and
‘‘derived,’’
Classification Categories
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Modern taxonomists use the following
classification:
– Species
– Genus
– Family
– Order
– Class
– Phylum
– Kingdom
– Domain
Classification Categories
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The higher the category, the more inclusive.
Organisms in the same domain have
general characteristics in common.
Phylogenetic (tribe” and “producing”) Trees
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Systematics is the study of the diversity of
organisms at all levels of organization.
One goal of systematics is to determine
phylogeny or evolutionary history of organisms
by gathering
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Fossil Record –
Homology –
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Molecular Data
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Protein comparison
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RNA and DNA comparison
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DNA hybridization
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Molecular Clock
Phylogenetic (tribe” and “producing”) Trees
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Phylogenetic tree is a diagram that:
– Indicates common ancestors and lines of
descent.
– Explain similarities and differences among
modern living groups.
– Reflect patterns of shared and unique
sections of DNA among groups of
animals.
Classification and Phylogeny
Tracing Phylogeny
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Fossil Record
– Fossil record is incomplete; thus, it is often hard
to tell to which group a fossil is related.
Homology is character similarity stemming from a
common ancestor.
– Convergent evolution is similarities in structure
in distantly related groups due to adaptation to
the environment
– Parallel evolution similarities in structure in
related group that cannot be traced to a
common ancestor.
Tracing Phylogeny
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Molecular data
– Protein comparison- distinction between
two organisms are determined by
sequencing of amino acids
– DNA and RNA comparison,
– DNA hybridization,
– Molecular clock
Systematics Today
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There are three main schools of systematics
today
– Cladistic
– Phenetics
– Traditional
Cladistic Systematics
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Uses shared derived characters to classify
organisms and arrange taxa (like
phylogenetic tree) called cladogram.
Phenetic Systematics
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In phenetic systematics, species are
classified according to the number of their
similarities.
– Ignores the possibility that some of the
shared characteristics are probably the
result of convergence or parallelism.
Traditional Systematics
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Traditional systematics mainly use
anatomical data to classify organisms and
construct phylogenetic trees based on
evolutionary principles.
– Stress both common ancestry and degree
of structural difference among divergent
groups.
 Not strict in making sure all taxa are
monophyletic.
Five-Kingdom System
The evolution of
organisms in the
five kingdoms is
most accurately
described as
Monera to
Protists, from
Protists
separately to
Fungi, Plants,
and Animals
Three-Domain System
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Molecular data suggest there are two
groups of prokaryotes, the bacteria and
archaea, that are so different, they should
be assigned to separate domains.
Three-Domain System
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Archaea live in extreme environments.
 Methanogens
 Halophiles
 Thermocidophiles
Three-Domain System
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Domain Eukarya contains unicellular and
multicellular organisms whose cells have a
membrane-bound nucleus.
– Sexual reproduction common.
– Contains 4 kingdoms:
 Protista
 Animals
 Fungi
 Plants
Review
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Taxonomy
– Binomial System
Species Identification
Classification Categories
Phylogenetic Trees
– Tracing Phylogeny
Cladistic Systematics
Phenetic Systematics
Classification Systems