Transcript Topic 1 Introduction to the Study of Life

Topic 1
Introduction to the Study of Life
1.4 Classification
Biology 1001
September 16, 2005
The Basic Concept of Grouping
• A natural human tendency is to group diverse items
according to similarities
• Taxonomy is the branch of biology that names and
classifies biological organisms
• Formalizes ordering of organisms into a series of
increasingly comprehensive groups
Figure 1.14 Classifying Life
THE Biological Species Concept
• The species is the “unit” of organization of biological
diversity
– “Species” is Latin for “kind” or “appearance”
– Species are usually morphologically distinct entities
– The primary definition of species is the biological species
concept attributable to Mayr (1942)
• The biological species concept defines a species as “a
population or group of populations whose members have the
potential to interbreed in nature to produce viable, fertile
offspring”
• Species are reproductively isolated from other species
Other Species Concepts
• Morphological species concept
– Differentiate species by their form (size, shape etc.)
• Paleontological species concept
– Describes morphological species known only from fossil record
• Ecological species concept
– Views species in terms of role or niche in community
• Phylogenetic species concept
– Defines species as branches on a tree of life
Concepts that emphasize unity; are useful in certain situations
Binomial Nomenclature
Attributable to Carolus Linnaeus1 and Systema naturae (1748)
• A two-part, Latinized, scientific1,2 name called the binomial
• The first part is the genus, the second is the specific epithet
• The genus is capitalized, the specific epithet is not
• Both parts are italicized (or underlined)
 Fringilla coelebs
Ursus americanus 
EXAMPLES
 Homo sapiens with Felis catus
Homarus americanus 
Two Important Points About Classification
Classification is hierarchical
Classification reflects phylogeny
Classification of Kingdoms and Domains
The Two-Kingdom System
 Early classification systems had two kingdoms
 Dates to Linnaeus who divided the world into plants and
animals (and rocks!)
 Based on macroscopic features such as motility
 Grouped together unrelated organisms – plants, fungi, and
bacteria were all placed in the plant kingdom
Classification of Kingdoms and Domains
The Five-Kingdom System
• Robert Whittaker proposed a system with five kingdoms
– Monera, Protista, Plantae, Fungi, and Animalia
Plantae
Fungi
Protista
Monera
Animalia
Classification of Kingdoms and Domains
The Downfall of the 5K System
• The 5K System is not a natural construct
• Problems with the 5K system
- Monera contains two distinct evolutionary lineages
- Protista is a “dumping ground” containing many unrelated lineages
• Neither of these kingdoms represents phylogeny (evolutionary
history)
• Based on new data, biologists now recognize three major
evolutionary lineages of life – the three domains
The Three Domain System
• The three domain system recognizes evolutionary relationships
– Replaces the five kingdom system
– Includes the domains Archaea, Bacteria, and Eukarya
– Superkingdoms, a taxonomic level higher than kingdom
• Each domain is split into one or more kingdoms
– Note that Monera and Protista are now obsolete kingdoms
– The number of kingdoms in the domains is still a matter for
scientific inquiry
The Three Domain System of Classification
Domain Archaea
Domain Bacteria
Universal ancestor
Domain Eukarya
Charophyceans
Chlorophytes
Red algae
Cercozoans, radiolarians
Stramenopiles (water molds, diatoms, golden algae, brown algae)
Chapter 27
Alveolates (dinoflagellates, apicomplexans, ciliates)
Euglenozoans
Diplomonads, parabasalids
Euryarchaeotes, crenarchaeotes, nanoarchaeotes
Korarchaeotes
Gram-positive bacteria
Cyanobacteria
Spirochetes
Chlamydias
Proteobacteria
One Current View of Biological Diversity
Chapter 28
Chapter 29
Fungi
Cnidarians (jellies, coral)
Chapter 32
Sponges
Choanoflagellates
Club fungi
Chapter 31
Animals
Bilaterally symmetrical animals (annelids,
arthropods, molluscs, echinoderms, vertebrates)
Plants
Sac fungi
Chapter 28
Arbuscular mycorrhizal fungi
Zygote fungi
Chytrids
Chapter 30
Amoebozoans (amoebas, slime molds)
Angiosperms
Gymnosperms
Seedless vascular plants (ferns)
Bryophytes (mosses, liverworts, hornworts)
One Current View of Biological Diversity
Chapters 33, 34
Comparing Systems of Higher Level Classification
– A Study Aid
Click for Animation 