Functional Morphology
• What is functional morphology?
• paleobiology and paleoecology of fossil & living organisms
• "function from form”
• adaptation adaptation is dynamic: Van Valen's "Red Queen"
hypothesis
• related to natural selection
Functional Morphology
• assume an organism's morphology served a purpose
• infer the function of the morphology
• example: a strange structure on a fossil: spines on the aperture of
a gastropod; spine must have served some function and the snail must have been
well adapted -- spines must have done their job well (to deter predators)
Functional Morphology
• Why is functional morphology studied?
• evolutionary processes are involved
• Understanding adaptations and their controls
• adaptive radiations: examples: insect wings, amniote egg, etc.
• important to paleoecology
• enables us to understand changes in life habits, ecology, and interactions
through time
• paleobiology of extinct strange and unusual organisms
Functional Morphology
• we assume morphology served a purpose; assume morphology has some adaptive
significance
• Must morphology have an adaptive significance?
• vestigial structures?
• structures could very well be non-adaptive and are there for other reasons
(like with vestigial structures)
• pleiotropy -- multiple effects are produced by the same gene: adaptations
or non-adaptations
• sexual selection - decreases fitness
• How do you recognize this in the fossil record?
Functional Morphology
• Testing for functional significance -- a paradigm -- a mechanical model
that assumes perfection
• Must adaptation be perfect: perfection and adaptation (optimality)
– assume that a structure must be perfectly adapted; structure must perform
like a perfectly designed machine
– inferring function from form - easier if perfection is assumed: can
apply engineering principles
• is this true?
• adaptation need not be perfect
• organism just has to adapted well enough to survive to reproduce
• "good enough" is just fine!
• Problems of redundancies:
• Multiple functions for same structure or multiple solutions to a problem
Methods of Study
• Direct Observation
– directly observe the function
– lucky, exceptional paleontological finds
• examples:
• industrial melanism in the peppered moth
– a real life adaptation: dark colored moths favored during industrial
revolution in Great Britain
• Green River Fm. fish, Eocene of Wyoming
– larger fish fossilized with smaller fish in its mouth; larger fish clearly
a carnivore
• cystoids: how did they live with respect to the substrate? - for long
time unclear
– Dev. cystoids from Iowa found with stems attached to the substrate
Methods of Study
• Study of Modern Relatives
- study living descendants to infer life habits of their ancestors (i.e., modern
analog approach)
- especially a good approach when studying living fossils
• look for homologous features: features which share a common ancestry
but do not necessarily serve the same function; must be careful of this last
part: if did not function the same, could be misleading
Methods of Study
• Study of Modern Relatives
• example: use of modern Nautilus to infer functional morphology of extinct
ammonites; both have homologous features
– buoyancy function of shell
• example: functional morphology of mussels -- two living forms with very
different life orientations; apply the position of muscle scars and byssal thread
regions to fossil forms
Methods of Study
Study of Analogous and Convergent Features
- analogous features look alike but do not share common ancestry (i.e., are
homoplasious); they are convergent
- - if you don't have homologous features, try using analogous ones
Methods of Study
• Study of Analogous and Convergent Features
• example: Apatosaurus -- long neck and large body previously interpreted
as walking around in fresh water
• - compared its morphology to that of elephants (terrestrial) and hippos
(aquatic):
a. vertebrae large with dorsal spines for muscle attachment - in terrestrial
b. chest oval in cross section in terrestrial; circular in aquatic
c. posture erect and not a sprawling posture
d. feet compact with heavy pad in terrestrial
Methods of Study
• Study of Mechanical Analogy
• Rudwick's paradigm method
• base functional interpretation on the similarity between organisms and
machines; design an optimal machine for that purpose and then compare organism's
morphology to that machine; how good is the match?
• example: flapping valves in brachiopods and Chinese furnaces, radiators
in cystoid respiratory structures
Methods of Study
Biomechanical Experimentation
- application of mechanical principles to the study of functional morphology
- examples: swimming in ammonites, strength of limb bones in tetrapod
- archeocyathans