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Comparative Anatomy Concepts & Premises

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

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Comparative Anatomy Concepts & Premises

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  1. Comparative AnatomyConcepts & 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 • Paedomorphosis- Ontogenetic changes where larval features of ancestor becomes morphological features of descendant • Juvenile character stage of ancestor is retained Figure 2.5 - (Left) larval state salamander with external, feathery gills; (Center) adult salamander that lost gills; (Right) adult axolotl salamander retains juvenile external gills.

  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 Figure 2.1- http://www.erin.utoronto.ca/~w3bio356/lectures/early_amniote.html Figure 2.2- http://courses.lib.odu.edu/biology/kcarpent/less10nte.html Figure 2.3- Kardong, K. Vertebrates: Comparative Anatomy, Function, Evolution. McGraw Hill, 2002. Figure 2.4- http://anthro.palomar.edu/animal/animal_2.htm Figure 2.5- http://evolution.berkeley.edu/evosite/evo101/IIIC6dDevochange2.shtml Figure 2.6- Morey, Darcy F. The Early Evolution of the Domestic Dog. American Scientist, Vol. 82, No. 4, p342. Figure 2.7- http://www.sciencemuseum.org.uk/exhibitions/lifecycle/12.asp Figure 2.8- http://www.edwardtbabinski.us/articles/snake_vestigial_limb.html Figure 2.9- http://anthro.palomar.edu/animal/animal_1.htm Figure 2.10- http://www.umanitoba.ca/faculties/science/biological_sciences/lab13/biolab13_3.html Figure 2.11- http://cas.bellarmine.edu/tietjen/images/agnaths.htm Figure 2.12- http://www8.nos.noaa.gov/coris_glossary/index.aspx?letter=a Figure 2.13- http://www.auburn.edu/academic/classes/zy/0301/Topic3/Topic3.html

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