1. Topics Need for systematics Applications of systematics
Linnaeus plus Darwin
Approaches in systematics
Principles of cladistics

2. Systematics - Study of diversity and evolutionary
Ch. 23 – Understanding Diversity:
Systematics pp
Systematics - Study of diversity and evolutionary
connections of organisms
Eukaryotes ~ mill spp. - Only ~1.9 mill spp. described
Quality of life - depends on tightly interwoven www of life
Human dependence
- Composition of atmosphere
- Fresh and sea water - critical food sources
- Pharmaceuticals - >40% - living systems (many from rain forests)
Many cultures directly depend on biodiversity of nature
Biodiversity - currently challenged by human impact at a multitude of levels - unpredictable disasters

3. classifying organisms Systematics
Ch. 23 – Understanding Diversity:
Systematics p
Taxonomy
Taxonomy - Science of
naming,
describing and
classifying organisms
Systematics
Systematics - Study of
biodiversity with the objective
of determining evolutionary
relationships of organisms
(phylogenetic analysis)

4. Why Systematics ? A universally accepted name to every organism
Ch. 23 – Understanding Diversity:
Systematics pp
Why Systematics ?
A universally accepted name to every organism
Grouping - Aid to memory
Understand evolution
Stronger interpretation of experimental results

5. Carolus Linnaeus, 1758 Two main features of Linnaean Taxonomy
Ch. 23 – Understanding Diversity:
Systematics pp
Carolus Linnaeus, 1758
Two main features of Linnaean Taxonomy
- Binomial Nomenclature
- Grouping into taxonomic categories

6. Binomial Nomenclature
Ch. 23 – Understanding Diversity:
Systematics p
Binomial Nomenclature
Generic name - Genus
Specific epithet - Species
Writing scientific names

7. Grouping into Taxonomic Categories
Ch. 23 – Understanding Diversity:
Systematics p. 476.
Grouping into Taxonomic Categories
Plantae
Terrestrial, multicellular, photosynthetic organisms
KINGDOM
PHYLUM
CLASS
ORDER
FAMILY
GENUS
SPECIES
Anthophyta
Vascular plants with flowers, fruits, and seeds
Monocotyledones
Monocots: Flowering plants with one seed leaf
(cotyledon) and flower parts in threes
Commelinales
Monocots with reduced flower parts, elongated
leaves, and dry 1-seeded fruits
Poaceae
Grasses with hollow stems; fruit is a grain; and
abundant endosperm in seed
Zea
Tall annual grass with separate female and
male flowers
Zea mays
Only one species in genus—corn
Domain Eukarya
on top
Picture in 7th Ed.

8. Domain Eukarya on top Ch. 23 – Understanding Diversity:
Systematics p. 477.
KINGDOM
PHYLUM
CLASS
ORDER
FAMILY
GENUS
SPECIES
Felis catus
Felis
Felidae
Carnivora
Mammalia
Chordata
Animalia
Domain Eukarya
on top

9. Clade-based PhyloCode rather than Linnaean hierarchical classification
Ch. 23 – Understanding Diversity:
Systematics pp
Clade-based PhyloCode
rather than Linnaean hierarchical classification

10. Systematists Reconstruct Phylogeny
Ch. 23 – Understanding Diversity:
Systematics p
Systematists Reconstruct Phylogeny
Systematics tries to reconstruct evolutionary relationships (phylogenies)
Homologous structures - important in establishing such relationships
Use homologous characters - structural, behavioral, physiological, developmental, molecular - not just morphological
Convergent evolution and reversed structures - reveal homoplasy - not always easy to distinguish from homology

11. Ch. 23 – Understanding Diversity:
Systematics p

12. Relationships among or within taxa
Ch. 23 – Understanding Diversity:
Systematics p
Relationships among or within taxa
Ideally, a taxon - evolutionary relationships
Monophyletic taxon - Ancestor and all of its decendents - a natural grouping - clade
Paraphyletic taxon - Common ancestor and some, but not all, of its descendents - reflects many/complex lines of evolutionary processes
Polyphyletic taxon - Several evolutionary lines - does not necessarily include the most recent common ancestor to all compared types – descendants from many ancestors
To be avoided/further analyzed. Do not represent natural associations

13. Tree-like Diagrams (Phylogenetic Trees)
Source: Biology of Plants.
Raven, Evert and Eichhorn. 1999

14. Shared Characters in Systematics
Ch. 23 – Understanding Diversity:
Systematics pp
Shared Characters in Systematics
Shared ancestral characters - traits in a common ancestor that persist in all descendants (plesiomorphic characters)
Shared derived characters - first appeared in more recent common ancestor(s) and found in the descendants of that ancestor only (synapomorphic characters)
A synapomorphic character in a more inclusive taxon becomes a plesiomorphic character in a narrower taxon

15. Different approaches to construct phylogenetic trees
Ch. 23 – Understanding Diversity:
Systematics p
Different approaches to construct phylogenetic trees
Phenetics – Neumerical taxonomy - use phenotypic and other similarities - shared characteristics (derived + ancestral) – use molecular similarities too – test statistical significance of similarities
Cladistics – Phylogenetic systematics - analyses shared derived characteristics to determine evol. relationships – use common ancestry and homologous characters
Evolutionary Systematics (Classical/traditional Evol. Syst.) – Use phenotypic similarity + shared ancestral and derived characters – recognizes (allows) paraphyletic taxa

16. Cladistics - Phylogenetic Systematics
Ch. 23 – Understanding Diversity:
Systematics pp
Cladistics - Phylogenetic Systematics
Focuses on common ancestry/branching sequence,
not evolutionary divergence/phenotypic similarity
Constructs cladograms using common ancestor
(based on shared derived characters determined
through outgroups), parsimony analysis (grouping
organisms based on minimum number of character
changes during evolution - simplest explanation - best)
and maximum likelihood
Outgroup is missing shared derived character(s) of
ingroup

17. Ch. 23 – Understanding Diversity:
Systematics pp
Outgroup Analysis
Characters and their states – states can be more than two

18. Ch. 23 – Understanding Diversity: Systematics pp. 487-489.

19. Ch. 23 – Understanding Diversity:
Systematics p

20. Evolutionary Systematics Vs. Cladistics
Ch. 23 – Understanding Diversity:
Systematics p. 487.
Evolutionary Systematics Vs. Cladistics

21. More monophyletic groups Minimum number of changes in characters
Ch. 23 – Understanding Diversity:
Systematics p
More monophyletic groups
Minimum number of changes in characters
- more accurate construction of the phylogeny
Use of modern molecular techniques - Molecular Systematics - Character
changes are changes on DNA - mutations
Use of computational Power