2. Homology
Homologous Structures – structures in different species that are similar because of common ancestry.

3. Analogy
Analogous Structures – similarity in structures due to adaptations from similar evolutionary pressures (convergent evolution) and not a common ancestor.

4. Convergent evolution occurs when similar environmental pressures and natural selection
Produce similar (analogous) adaptations in organisms from different evolutionary lineages
Australian Mole –marsupial mammal
North American Mole – placental mammal

5. Sorting Homology from Analogy
A potential misconception in constructing a phylogeny
Is similarity due to convergent evolution, called analogy, rather than shared ancestry
Ex: Humans, gorillas, and ravens have the ability to problem-solve, and are highly intelligent. Humans and gorillas share ancestry: homology. Ravens are in a separate phylum (birds), so developed their intelligence separately from humans.

6. Linking Classification and Phylogeny
Systematists depict evolutionary relationships
In branching phylogenetic trees

7. Each branch point
Represents the divergence of two species

8. “Deeper” branch points
Represent progressively greater amounts of divergence

9. “KLADOS” = Greek word meaning “BRANCH” or “SPROUT”
Cladogram - a shows pattern of shared, inherited characteristics; a “graphic organizer” based on measurable traits and not evolutionary relationships.

10. Cladogram for Transportation
Wheels are the most ancestral (oldest).
Wings are the most derived (newest).

11. Construct a Cladogram for Us!

12. Gorilla
Four limbs
Fur
No tail

13. Tiger
Four limbs
Fur
Tail

14. Lizard
Four limbs
Tail

15. Fish
Tail

16. Chimpanzee
Four limbs
Fur
No tail

17. Clade With 4 Limbs

18. Clade With Fur

19. Clade With No Tail

20. Characteristics (Traits) for Constructing this Cladogram
Tail is the most ancestral
Four limbs is the oldest derived trait
Fur is a later derived trait
Loss of tail is the most derived trait

21. One Possible Cladogram
Four Limbs

22. Where’s the Tail?
How do we know the gorilla and chimpanzee have lost their tail?
Sometimes cladists must compare embryological development and internal anatomy to determine relatedness.
May not be exactly the same structures.

23. Coccyx- Primate Vestigial Tails
Human Pelvic Girdle
Gorilla Pelvic Girdle
Vestigial Structure - historical remnants of a structure that has little or no use in a modern organism but had a function in ancestors.

24. A Vertebrate Cladogram
Vertebrae
Lancelet
Outgroup

25. What is the shared primitive character for this clade? Ans:
Birds
Mammals
Reptile
Amphibian
Fish
Four Limbs
Amniotic Egg
Endothermic
Fur
Feathers
Vertebrae
Lancelet
Outgroup
What is the shared primitive character for this clade?
Ans:

26. Birds
Mammals
Reptile
Amphibian
Fish
Four Limbs
Amniotic Egg
Endothermic
Fur
Feathers
Vertebrae
Lancelet
Outgroup
What is the shared derived character for amphibians, reptiles, birds & mammals?
Ans: Four Limbs
For reptiles, birds & mammals?
Ans: Amniotic Egg

27. Phylogenetic Trees and Timing
A cladogram is not a phylogenetic tree; may need more information (fossils, molecular systemics, etc.).
Any chronology represented by the branching pattern of a phylogenetic tree
Is relative rather than absolute in terms of representing the timing of divergences.

28. Phylograms
In a phylogram:
The length of a branch reflects the number of genetic changes that have taken place in a particular DNA or RNA sequence in that lineage.
A phylogram of homologous hedgehog genes.
Outgroup

29. Ultrametric Trees
In an ultrametric tree:
The branching pattern is the same as in a phylogram, but all the branches that can be traced from the common ancestor to the present are of equal length.
Outgroup

30. A Rule about Phylogenetic Trees
William of Ockham – 14th Cent. English philosopher, stated that, when all qualities of hypotheses are equal, the simplest explanation for a phenomenon is usually correct; Occam’s Razor: "entities must not be multiplied beyond necessity" (entia non sunt multiplicanda praeter necessitatem).
Parsimony – stingy, economical, fewest complications.

31. Phylogenetic Trees are Hypotheses
Among phylogenetic hypotheses
The most parsimonious tree is the one that requires the fewest evolutionary events to have occurred in the form of shared derived characters.
The best hypotheses for phylogenetic trees
Are those that fit the most data: morphological, molecular, and fossil.

32. The Case of the 4- Chambered Heart:
Analogous vs. Homologous
Type of heart arose twice independenly.
Not the most parsimonious.
Crocodilians

33. Molecular Clocks A molecular clock:
Is a yardstick for measuring the absolute time of evolutionary change based on the observation that some genes and other regions of genomes appear to evolve at constant rates.
The rRNA genes change very slowly; good clocks for distant time measurments (millions of years).
Mitochondrial DNA (mtDNA) changes quickly and useful in recent evolutionary changes; used to explore the relationships of groups of humans (thousands of years).

34. Overview: Welcome to Your Kingdom The animal kingdom
Extends far beyond humans and other animals we usually encounter

35. Several characteristics of animals
Animal are multicellular, heterotrophic eukaryotes with tissues that develop from embryonic layers
Several characteristics of animals
Sufficiently define the group

36. The history of animals may span more than a billion years
The animal kingdom includes not only great diversity of living species
But the even greater diversity of extinct ones as well

37. The common ancestor of living animals
May have lived 1.2 billion–800 million years ago
May have resembled modern choanoflagellates, protists that are the closest living relatives of animals.
Single cell
Stalk

38. Animals can be characterized by “body plans”
One way in which zoologists categorize the diversity of animals
Is according to general features of morphology and development
A group of animal species
That share the same level of organizational complexity is known as a grade; grade is not necessarily a clade (may not be monophyletic)

39. Patterns of Organization
4 Ways of Animal Organization:
Symmetry (Asymmetry, Radial, Bilateral)
Tissue Organization (Diploblastic, Triploblastic)
Body Cavity Development (Acoelomate, Pseudocoelomate, Coelomate)
Embryological Development (Protostome and Deuterostome)