1. Comparative Anatomy Concepts & Premises
Note Set 1
Chapters 1 & 2

2. Phylogeny Historical relationship between organisms or lineages
Ancestry shown by phylogenetic tree
Phylogenetic Systematics- shows relationships from past to present
Shows evolutionary relationships
Figure 2.1

3. Major Vertebrate Groups
Figure 2.2

4. Cladistics Method for studying phylogeny
Shows ancestry of derived features
Figure 2.3
Advanced structures are derived, synapomorphic
Primitive structures are not derived, ancestral, symplesiomorphic

5. Convergence- organism response to similar environment
Similar structures yet distantly related organisms
Ex: limbs of fishes and marine mammals
Parallelism- structure similarities in closely related organisms
Similar morphology due to parallel evolution
Ex: Dog and gray wolf skull
Figure 2.4

6. Paedomorphosis
Figure (Left) larval state salamander with external, feathery gills; (Center) adult salamander that lost gills; (Right) adult axolotl salamander retains juvenile external gills.
Paedomorphosis- Ontogenetic changes where larval features of ancestor becomes morphological features of descendant
Juvenile character stage of ancestor is retained

7. Paedomorphosis (cont.)
Figure 2.6: Natural selection pressures on the wolf may have lead to the formation of a new species, the domestic dog. The prehistoric adult dog skull (center) can be compared to the adult wolf skull (left) and particularly the juvenile wolf skull (right).

8. Paedomorphosis (cont.)
Neoteny- delayed rate of somatic development
Progenesis- precocious sexual maturation in morphological juvenile
Behavioral Paedomorphology- juvenile behavioral stage retained
Ex: wolf pup and domestic dog
Heterochrony- change in rates of character development during phylogeny

9. Generalized- structure with broad function
Ex: human hand
Specialized- structure with restricted function
Ex: single digit hand
Modification- change from previous state, may be preadaptive
Preadaptation- current trait that will be useful in future
Ex: binocular vision and thumb

10. Higher vs. Lower Vertebrates
Amniotes- higher vertebrates with amniotic sac
Ex: reptiles, birds, mammals
Anamniotes- lower vertebrates without amniotic sac
Ex: fish, amphibians
Amnion- membrane sac that surrounds embryo
Cleidoic egg- amniotic egg with shell

11. Serial homology- serial repetition of body parts in single organism
Ex: Somites
Figure 2.7: Somite formation in 4 week old embryo.

12. Vestigial
Vestigial- phylogenetic remnant that was better developed in ancestor.
(e.g., human appendix, fruit fly wings,
python leg spurs)
Figure 2.8: Ball python spurs.

13. Rudimentary
Phylogenetic sense- structure is fully exploited by a descendant
Ex: rudimentary lagena in fish (sac of semicircular canals) develops into organ of Corti in mammals
Ontogenetic sense- structure is underdeveloped or not fully developed from embryo to adult
Ex: Muellerian tract in females develops into reproductive tract; yet in males, duct is rudimentary
Ex: Woffian duct in males develops into sperm duct; yet in females, duct is rudimentary

14. Adaptive Radiation- diversification of species into different lines through adaptation to new ecological niches
Figure 2.9: Branching evolution; increased diversity.

15. Sea Squirt Free Swimming Larva
Figure 2.10: Larval form of sea squirt.
Figure 2.11: Lamprey larval structures.
Larval stage of sea squirt resembles vertebrate tadpole
Developed notochord and dorsal nerve cord
Rudimentary brain and sense organs

16. Sea Squirt Sessile Adult
Figure 2.12: Adult sea squirt.
Figure 2.13: Adult sea squirt structures (see book figure 3.4).
Once larva attaches, notochord and nervous system disappear
Resembles invertebrate

17. Literature Cited
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Figure 2.3- Kardong, K. Vertebrates: Comparative Anatomy, Function, Evolution. McGraw Hill, 2002.
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Figure 2.6- Morey, Darcy F. The Early Evolution of the Domestic Dog. American Scientist, Vol. 82, No. 4, p342.
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