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What is adaptation?
A trait that enhances fitness and that arose historically as a result of natural selection for its current biological role.
Requires;
- Feature
- More offspring reproducing
- Favoured by natural selection
- Appeared in conjunction with its current function in its environment (was not previously used for another function)
How do we apply evolutionary methods to test for adaptations?
- phylogenetic comparative methods
What are non-adaptive explanations for animal design?
- Phylogenetic constraint or "baggage"
- Design constraints prevent the optimal
- Sexual selection
- Neutral features ("spandrels")
- Co-variation with other traits
- Exaptation
- Random genetic drift
What are some examples of important evolutionary novelties and constraints in vertebrate locomotor design?
Earliest vertebrates:
- Body segments organized into myomeres with blocks of muscle separated by myosepta
- Contracted in waves to propel the body forward
- Pectoral, then pelvic fins evolved to supplement role of axial column in generating thrust and lift
- Both fins gained bony supports that expanded distally in fish closely related to tetrapods
What are adaptive features for economy and speed?
For economy and speed;
- Continuum of limb posture (Planti/Digiti/Unguligrade)
- Elongation of distal limb for speed
- Lightening of the distal limb to minimise cost of leg swing
- Reduction in number of bones
- Muscle replaced by energy- efficient tendons that act as pulleys and springs
- Motion restricted to sagittal plane
What are adaptive features for economy?
- High 'aerobic scope' (10-50X in athletic animals (about 5 in lizards))
Temperature regulation; evaporation (sweating, panting), brain temperature regulation (carotid rete)
- Mitochondrial density in muscle
- Red blood cell volume A}
What is 'Parasite power'?
- The power required to overcome drag on body
What is the formulae for parasite power?
What is 'Profile power'?
- The power required to overcome drag on wings
What is the formulae for profile power?
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