UNIT IV
DIVERSITY OF LIVING THINGS
Scientific Classification
CLASSIFICATION
• the grouping of organisms by similarities
• Biological classifications are based on how
organisms are related.
Group A
Group B
Why Do We Classify Organisms?
• Biologists group organisms to represent
similarities and proposed relationships.
• Classification systems change with expanding
knowledge about new and well-known organisms.
Classification
• Binomial Nomenclature
– Two part name (Genus, species)
• Hierarchical Classification
– Seven Taxonomic Catagroies
• Systematics
– Study of the evolution of biological diversity
Taxonomy: the branch of biology
concerned with the grouping and naming
of organisms; the study of classification
Taxonomy
• Organisms are
classified into a
hierarchy of groups
and subgroups based
on similarities that
reflect their
relationships over a
period of time.
Cladogram or Phylogenic Tree
• A branching, treelike
diagram in which the
endpoints of the branches
represent specific species
of organisms.
• It is used to illustrate
phylogenetic relationships
and show points at which
various species have
diverged from common
ancestral forms.
Animation - Phylogenetic
Trees
Taxonomic Diagrams
Mammals
Turtles
Phylogenetic
Tree
Lizards and
Snakes
Crocodiles
Birds
Mammals
Turtles
Lizards and
Snakes
Crocodiles
Cladogram
Birds
Tree of life
Biology: Samples
-
HISTORY:
• Aristotle- developed the 1st method
of classification
• He divided all living things into 2
major groups
Aristotle’s Groups
• He divided all living things into 2 major
groups
• 1. Plants
– classified by size and structure
2. Animals
– classified by habitat (where they lived)
HISTORY: Aristotle
• Problems with his system:
– Frogs live in both water and on land
Bats,
birds and flying insects were grouped together
• Kingdom – largest group
• Phylum (sing.)
– Phyla (pl.)(Plants don’t
have phyla, they have
divisions.)
•
•
•
•
•
Class
Order
Family
Genus
Species
Kingdom
Phylum
Class
Order
Family
These two
taxa make up
the scientific
name.
Genus
Species
K__________ p__________ c_________
o___________ f________ g_________
s________.
King Phillip came over for great soup.
HISTORY:
• Carolus Linnaeusdeveloped the
modern system of
classification
• Father of Taxonomy
Binomial Nomenclature
• Carolus von Linnaeus
• Two-word naming system
– Genus
• Noun, Capitalized,
Underlined or Italicized
– Species
• Descriptive, Lower Case,
Underlined or Italicized
Binomial Nomenclature
 Binomial nomenclature is a standard way of
identifying a species with a scientific twoword name.
The first word is the genus name and the
second the species name.
 Scientific name - 2 Latin names
 - Genus and species
 - Capitalize the first letter of the genus
 - Do NOT capitalize the species
 - ALWAYS underline or use italics
Ex. Homo sapiens
Binomial Nomenclature
Scientific Name:
Homo sapiens
Common Name:
Albert Einstein
Binomial Nomenclature
Scientific Name:
Rudbeckia hirta
Common Name:
Gloriosa daisy
or Black-eyed Susan
Binomial Nomenclature
Scientific Name:
Pinus virginianis
Common Name:
Virginia Pine
Binomial Nomenclature
Scientific Name:
Harmonia axyridis
Common Name:
Asian Ladybug
Binomial Nomenclature
Scientific Name:
Ophiophagus
hannah
Common Name:
King Cobra
MODERN CLASSIFICATION SYSTEM
• Organisms are grouped together on
the basis of:
– Similarity in structure
Panthera leo
Felis rufus
Felis domesticus
Similarity in structure
Canis lupus
Similarity in structure
Canis latrans
Similarity in structure
Canis domesticus
Organisms are grouped together on the basis of:
• Similarity in genetic makeup
(biochemistry)
• Similarities among organisms
on the structural and
metabolic levels are reflected
in the large degree of
similarity in proteins and
nucleic acids of different
organisms.
• Diversity is the product of
variations in these molecules.
Organisms are grouped together on the
basis of:
• Similarity of embryonic development
Evolution: Library: Common Past, Different Paths
Organisms are grouped together on the
basis of:
• Similarity in evolutionary history
– Phylogeny: the evolutionary history of
a species based on comparing
relationships between species using the
fossil record
Organisms are grouped together on the
basis of:
• Similarity in behavior
Systematics:
Evolutionary Classification of Organisms
• Systematics is the study of the evolution of
biological diversity, and combines data from the
following areas.
–
–
–
–
Fossil record
Comparative homologies
Cladistics
Comparative sequencing of DNA/RNA among
organisms
– Molecular clocks
• Classification is based on close
evolutionary relationships of
organisms.
– Organisms classified in the same taxa
(pl.) (taxon, sing.) share a common
ancestry. They have evolved from the
same common ancestral organism.
Evolutionary Relationships
• Classification is hierarchal
– each successive level is smaller and more closely
related than the one before it
Species
 organisms that belong to the same species
can mate AND produce FERTILE
offspring.
• Horses and donkeys can mate.
– They produce a mule.
• Mules are INFERTILE
+
=
• Lions and tigers can mate.
– They produce a liger.
• Ligers are INFERTILE
+
=
Why use scientific names?
• Common names do not indicate how
organisms are related or classified.


Common names can be misleading.
(e.g., seahorse, weeping willow)
Organisms with more than one
common name leads to mass
confusion.
Why Latin?
• Latin is no longer spoken, and
therefore, does not change as spoken
languages do.
 So, scientific names remain the same
forever.
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Scientific Classification - Father Michael McGivney