Identifying Naming & Classifying Species
1.1 Identifying Species
 Scientists have various methods of deciding what species an organism belongs to they are called
Species Concepts
1. Morphological species concepts
 Focus on morphology (body shape, size, etc) to decide whether similar
organisms represent different species
 Advantage: simple to use
 Disadvantage: Hard to decide how much difference is too much because all
populations are made up of non-identical individuals
2. Biological species concepts
 Based on whether 2 organisms can produce viable, fertile offspring
 Advantage: widely used in science
Disadvantage: cannot be applied in all cases: e.g., fossil records
(because those species are no longer reproducing), e.g., populations
that are physically separated which results in never having a chance to
interbreed; e.g., species that reproduce via asexual reproduction.
3. Phylogenetic species concepts
 Focuses on the evolutionary relationships among organisms. As species
change over time they branch into 2 separate phylogenetic species.
 Advantage: able to incorporate DNA evidence, can be applied to extinct
species
 Disadvantage: evolutionary histories are not known for all species.
Naming Species
 After scientists have decided which organisms are actually separate species, a name is assigned to
the species
Taxonomy = branch of biology that identifies, names & classifies species based on their features
 Carolus Linnaeus is known as the father of taxonomy. He is credited with developing the system for
naming species called Binomial Nomenclature
Binomial Nomenclature – the system of giving a 2-word Latin name to each species
 The first part is the Genus (taxonomic group of closely related species) and is always Capitalized
 The second part is the species and is written in lower case
 When the name is typed it is always italicized. When the name is hand written it is always
underlined.
Example: Humans have the Latin name Homo sapiens
Genus: major group to which
organism belongs (first letter
capitalized)
Species: specific species to which the organism
belongs (first letter lower case)
Classifying Species
 Classification - the grouping of organisms based on a set of criteria that helps to organize and
indicate evolutionary relationships.
 Hierarchical Classification - classifies organisms by
arranging species based on categories from most
general to most specific. This is known as a nested
system.
Taxonomic Categories
 Taxonomic categories are used to classify organisms
that have been identified.
 The categories or groupings are arranged in a
hierarchy (most general to most specific)
 Each level or category is known as the rank. The particular classification of an organism at each rank
level is called the taxon (plural: taxa).
 There are eight ranks. Domain is the most general, containing the most species. The species rank is
specific to one species.
Example: Humans
World Comparison
DOMAIN
Eukarya
Earth
KINGDOM
Animalia
Continent
PHYLUM
Chordata
Country
Mammalia
Province
Primates
Region
Hominidae
City
GENUS
Homo
Street
SPECIES
Homo sapiens
Street + house
number
CLASS
ORDER
FAMILY
INCREASING DIVERSITY
INCREASING SIMILARITY
INCREASING DIVERSITY
Taxonomic Classification
1.3 Kingdoms & Domains
Kingdoms
 The second most general rank is kingdom
 There are six different kingdom taxa in the classification system.
 There is incredible structural diversity (internal and external forms) within the kingdoms, even
though species are grouped together.
 The six kingdoms are:
1. Archaea (sometimes called Archaebacteria)
2. Bacteria (sometimes called Eubacteria)
3. Protista
4. Fungi
5. Plantae
6. Animalia
 The main characteristics used to determine the kingdom are cell level distinctions, for example:
-number of cells (unicellular or multicellular)
-nutrition (autotroph or heterotroph)
-primary means of reproduction (asexual or sexual)
1.

2.

Two major cell types:
Prokaryotic cells
Most ancient, no membrane-bound nucleus
Eukaryotic cells
Larger, complex, membrane-bound nucleus
Domains
 As scientists continued to analyze organisms in the kingdoms Bacteria and Archaea the category
domain was added to the classification system.
 Scientists found that there were such differences between these 2 groups that they added a higher
rank Domain
 The 3 domains are: Bacteria, Archaea and Eukarya