1. Phylogeny & Systematics
Chapter 25.
Phylogeny & Systematics
AP Biology

2. Phylogeny & Systematics  Phylogeny
 evolutionary history of a species
 based on common ancestries inferred from
 fossil record
 morphological & biochemical resemblances  molecular evidence
 Systematics
 connects classification system to phylogeny by categorizing & naming
organisms
AP Biology

3. Biologists draw on the fossil record
Which provides information about ancient organisms
Figure 25.1

4. Currently, systematists use
Morphological, biochemical, and molecular comparisons to infer evolutionary relationships
Figure 25.2

5.  Sedimentary rock are richest source of fossils
Fossil record
 Sedimentary rock are richest source of fossils
 fossil record is a substantial, but
incomplete, chronicle of evolutionary history
 incomplete historical documents of biology  history of life on Earth
is punctuated by
mass extinctions
5000 year old ice mummy found on an Alpine ridge dividing Austria from Italy at 10,500 feet
above sea level.A

6. Though sedimentary fossils are the most common
Paleontologists study a wide variety of fossils
Figure 25.4a–g
(a) Dinosaur bones being excavated from sandstone
(g) Tusks of a 23,000-year-old mammoth, frozen whole in Siberian ice
(e) Boy standing in a 150-million-year-old dinosaur track in Colorado
(d) Casts of ammonites, about 375 million years old
(f) Insects preserved whole in amber
(b) Petrified tree in Arizona, about 190 million years old
(c) Leaf fossil, about 40 million years old

7. Morphological and Molecular Homologies
In addition to fossil organisms
Phylogenetic history can be inferred from certain morphological and molecular similarities among living organisms
In general, organisms that share very similar morphologies or similar DNA sequences
Are likely to be more closely related than organisms with vastly different structures or sequences

8. Sorting Homology from Analogy
A potential misconception in constructing a phylogeny
Is similarity due to convergent evolution, called analogy, rather than shared ancestry

9. Convergent evolution occurs when similar environmental pressures and natural selection
Produce similar (analogous) adaptations in organisms from different evolutionary lineages
Figure 25.5

10. Evaluating Molecular Homologies
Systematists use computer programs and mathematical tools
When analyzing comparable DNA segments from different organisms
Figure 25.6
C C A T C A G A G T C C
C C A T C A G A G T C C
C C A T C A G A G T C C
G T A
Deletion
Insertion
C C A T C A A G T C C
C C A T G T A C A G A G T C C
C C A T C A A G T C C
C C A T G T A C A G A G T C C
1 Ancestral homologous DNA segments are identical as species 1 and species 2 begin to diverge from their common ancestor.
2 Deletion and insertion mutations shift what had been matching sequences in the two species.
3 Homologous regions (yellow) do not all align because of these mutations.
4 Homologous regions realign after a computer program adds gaps in sequence 1. 1 2
A C G G A T A G T C C A C T A G G C A C T A
T C A C C G A C A G G T C T T T G A C T A G
Figure 25.7

11. Concept 25.2: Phylogenetic systematics connects classification with evolutionary history
Taxonomy
Is the ordered division of organisms into categories based on a set of characteristics used to assess similarities and differences

12. Binomial Nomenclature
Is the two-part format of the scientific name of an organism
Was developed by Carolus Linnaeus

13. Hierarchical Classification
Linnaeus also introduced a system
For grouping species in increasingly broad categories
Panthera
pardus
Felidae
Carnivora
Mammalia
Chordata
Animalia
Eukarya
Domain
Kingdom
Phylum
Class
Order
Family
Genus
Species
Figure 25.8

14. Linking Classification and Phylogeny
Systematists depict evolutionary relationships
In branching phylogenetic trees
Panthera pardus (leopard)
Mephitis mephitis (striped skunk)
Lutra lutra (European otter)
Canis familiaris (domestic dog)
Canis lupus (wolf)
Panthera
Mephitis
Lutra
Canis
Felidae
Mustelidae
Canidae
Carnivora
Order
Family
Genus
Species
Figure 25.9

15. Each branch point Represents the divergence of two species Leopard
Domestic cat
Common ancestor

16. “Deeper” branch points
Represent progressively greater amounts of divergence
Leopard
Domestic cat
Common ancestor
Wolf

17. A clade within a cladogram
Concept 25.3: Phylogenetic systematics informs the construction of phylogenetic trees based on shared characteristics
A cladogram
Is a depiction of patterns of shared characteristics among taxa
A clade within a cladogram
Is defined as a group of species that includes an ancestral species and all its descendants
Cladistics
Is the study of resemblances among clades

18. Cladistics
Clades
Can be nested within larger clades, but not all groupings qualify as clades

19. A monophyletic clade
Is a grouping that consists of the ancestor species and all its descendants
(a) Monophyletic. In this tree, grouping 1, consisting of the seven species B–H, is a monophyletic group, or clade. A mono- phyletic group is made up of an ancestral species (species B in this case) and all of its descendant species. Only monophyletic groups qualify as legitimate taxa derived from cladistics.
Grouping 1 D C E G F B A J I K H
Figure 25.10a

20. A paraphyletic clade
Is a grouping that consists of an ancestral species and some, but not all, of the descendants
(b) Paraphyletic. Grouping 2 does not meet the cladistic criterion: It is paraphyletic, which means that it consists of an ancestor (A in this case) and some, but not all, of that ancestor’s descendants. (Grouping 2 includes the descendants I, J, and K, but excludes B–H, which also descended from A.) D C E B G H F J I K A
Grouping 2
Figure 25.10b

21. A polyphyletic grouping
Includes numerous types of organisms that lack a common ancestor
Grouping 3
(c) Polyphyletic. Grouping 3 also fails the cladistic test. It is polyphyletic, which means that it lacks the common ancestor of (A) the species in the group. Further- more, a valid taxon that includes the extant species G, H, J, and K would necessarily also contain D and E, which are also descended from A. D C B E G F H A J I K
Figure 25.10c

22. Shared Primitive and Shared Derived Characteristics
In cladistic analysis
Clades are defined by their evolutionary novelties

23. A shared primitive character
Is a homologous structure that predates the branching of a particular clade from other members of that clade

24. A shared derived character
Is an evolutionary novelty unique to a particular clade

25. Systematists use a method called outgroup comparison
Outgroups
Systematists use a method called outgroup comparison
To differentiate between shared derived and shared primitive characteristics

26. Phylograms In a phylogram
The length of a branch in a cladogram reflects the number of genetic changes that have taken place in a particular DNA or RNA sequence in that lineage
Drosophila
Lancelet
Amphibian
Fish
Bird
Human
Rat
Mouse
Figure 25.12

27. The Universal Tree of Life
The tree of life
Is divided into three great clades called domains: Bacteria, Archaea, and Eukarya
The early history of these domains is not yet clear
Bacteria
Eukarya
Archaea
4 Symbiosis of chloroplast ancestor with ancestor of green plants 1
3 Symbiosis of mitochondrial ancestor with ancestor of eukaryotes 4
Billion years ago 3 2
2 Possible fusion of bacterium and archaean, yielding ancestor of eukaryotic cells 2 3
1 Last common ancestor of all living things 1
Origin of life 4
Figure 25.18