1. Biology, 9th ed,Sylvia Mader
Chapter 20
Chapter 20
Classification of Living Things
Classification of Living Things

2. Outline Taxonomy Binomial System Species Identification
Classification Categories
Phylogenetic Trees
Systematics
Taxonomy (naming of organisms)
Classification (placing species in the proper categories)
Systematics Today
Cladistic Systematics
Phenetic Systematics
Classification Systems
The Five Kingdom System
The Three Domain Ssytem

3. Began with the ancient Greeks and Romans
Taxonomy
Branch of biology concerned with identifying, naming, and classifying organisms
Began with the ancient Greeks and Romans
Aristotle classified organisms into groups such as horses, birds, and oaks
John Ray (1627–1705)
Believed that each organism should have a set name
Otherwise, “men…cannot see and record accurately.”

4. Classifying Organisms

5. Taxonomy: Binomial System
Mid-eighteenth century, Linnaeus developed the binomial system of nomenclature
First word is genus name
Second word is specific epithet
Refers to one species (of potentially many) within its genus
A species is referred to by the full binomial name (Genus species)
Genus name can be used alone to refer to a group of related species

6. Taxonomy: Distinguishing Species
Distinguishing species on the basis of structure can be difficult
Members of the same species can vary in structure
Attempts to demonstrate reproductive isolation is problematic because:
Some species hybridize, and
Reproductive isolation is difficult to observe

7. Hybridization between species Zebroids are horse-zebra hybrids.

8. Classification Categories
Modern taxonomists use the following classification:
Species
Genus – one or more species
Family – one or more genera
Order – one or more families
Class – one or more orders
Phylum – one or more classes
Kingdom – one or more phyla
Domain – one or more kingdoms

9. Eukarya- membrane-bounded nucleus
Animalia- motile, multicellular, internal cavity for digestion of nutrients
Chordata- organisms that at one time have a dorsal hollow nerve cord, a notochord, pharyngeal pouches, and a postanal tail
Mammalia- warm-blooded vertebrates with mammary glands; body with hair;
Primates- well-developed brain opposable thumb
Hominidae- upright stance and bipedal locomotion
Homo- Full brain development, hand anatomy for making tools
Species- sapiens modern humans; speech centers

10. Classification Categories
The higher the category, the more inclusive
Organisms in the same domain have general characteristics in common
In most cases, classification categories can be subdivided into additional categories
Superorder
Order
Suborder
Infraorder

11. Systematics - the diversity of organisms at all levels
Phylogenetic Trees
Systematics - the diversity of organisms at all levels
One goal of systematics is to determine phylogeny (evolutionary history) of a group
Phylogeny often represented as a phylogenetic tree
A diagram indicating lines of descent
Each branching point:
Is a divergence from a common ancestor
Represents an organism that gives rise to two new groups

12. Phylogenetic Trees
Classification lists the unique characters of each taxon and is intended to reflect phylogeny
Primitive characters:
Present in all members of a group, and
Present in the common ancestor
Derived characters:
Present in some members of a group, but
Absent in the common ancestor

13. Tracing Phylogeny Fossil Record Homology
Fossil record is incomplete
It is often difficult to determine the phylogeny of a fossil
Homology
Refers to features that stem from a common ancestor
Homologous structures are related to each other through common descent
Analogy-wings of an insect and the wings of a bat are analogous
Similarity due to convergence-similar characters in distantly related lines of descent.

14. Ancestral Angiosperm

15. Tracing Phylogeny Convergent Evolution Parallel Evolution
The acquisition of a feature in distantly related lines of descent
The feature is not present in a common ancestor
Parallel Evolution
The acquisition of a feature in two or more related lineages

16. Convergent Evolution-both like dry, hot environments & succulent with spiny leaves but not closely related.

17. Molecular Data Protein Comparisons RNA and DNA Comparisons
Immunological techniques
Degree of cross reaction used to judge relationship
Amino acid sequencing
Similar sequence in same protein indicates close relationship
RNA and DNA Comparisons
Systematics assumes:
Two species with similar base-pair sequences are assumed to be closely related
Two species with differing base-pair sequences are assumed to be only distantly related
Molecular Clocks
Use non adaptive nucleotide sequences
Assumed constant rate of mutation over time

18. Ancestry of Giant Pandas

19. Cladistic Systematics
Traces evolutionary history of the group under study
Uses shared derived characters to:
Classify organisms, and
Arrange taxa into a cladogram
A cladogram is a special type of phylogenetic tree
A clade is an evolutionary branch that includes:
A common ancestor, together with
All its descendent species

20. Constructing a Cladogram

21. Cladists are always guided by the principle of parsimony
The arrangement requiring the fewest assumptions is preferred
This would:
Leave the fewest number of shared derived characters unexplained
Minimize the number of assumed evolutionary changes
The reliability of a cladogram is dependent on the knowledge and skill of the investigator

22. Cladistic Versus Traditional View of Reptilian Phylogeny

23. Phenetic Systematics
Assumes it will never be possible to construct a truly phylogenetic classification system
Species are classified according to the total number of shared similarities
Disregards assumed phylogenetic considerations
Ignores issues of convergent or parallel evolution

24. Traditional Systematics
Mainly uses anatomical data
Classify organisms using assumed phylogeny with emphasis on phenotype
Stress both common ancestry and degree of structural difference among divergent groups
Construct phylogenetic trees by applying evolutionary principles to categories
Not strict in making sure all taxa are monophyletic

25. Classification Systems
Until the middle of the twentieth century, biologists recognized only two kingdoms
Plantae (plants)
Animalia (animals)
Protista (protists) were added as third kingdom in the 1880s
Whittaker expanded to five kingdoms in 1969 by adding Fungi and Monera

26. Three-Domain System-compare table 20.3
The Bacteria and Archaea are so different they have been assigned to separate domains
Similar in that both are asexually reproducing unicellular prokaryotes
Distinguishable by:
Difference in rRNA base sequences
Plasma membrane chemistry
Cell wall chemistry

27. Unicellular and multicellular organisms
Three-Domain System
Domain Eukarya
Unicellular and multicellular organisms
Cells with a membrane-bounded nucleus
Sexual reproduction common
Contains four kingdoms
Kingdom Protista
Kingdom Fungi
Kingdom Plantae
Kingdom Animalia

28. The Three-Domain System of Classification

29. The Three Domains of Life

30. Review Taxonomy Binomial System Species Identification
Classification Categories
Phylogenetic Trees
Systematics
Taxonomy (naming of organisms)
Classification (placing species in the proper categories)
Systematics Today
Cladistic Systematics
Phenetic Systematics
Classification Systems
The Five Kingdom System
The Three Domain System

31. Biology, 9th ed,Sylvia Mader
Chapter 20
Ending Slide Chapter 20
Classification of Living Things
Classification of Living Things