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Characteristics
• Bipedal
• Feathers (diagnostic)– Insulation– Lift and thrust
• Toothless bills covered with horny sheath
• Wings
• Ability to fly*
Characteristics (cont.)
• Adaptations associated with flight:
– Skeleton– Musculature– Physiology– Reproductive system– CNS– etc…
Adaptive Radiations (within adaptive radiations)
• Evolution of ecological diversity within a rapidly multiplying lineage (Schluter, 2000)
• 150-160 MYA
• >10,000 species extant– Fraction of what has existed
A note on Avian Classification
• Imprint of Linneaus 1758– Binomial nomenclature
• Upupa epops
– Standard English Names (“Common Name”)
– In NA, both established by AOU
Genus species
KingdomPhylumClassOrderFromGenusspecies
Classification of three species of woodpeckers
Taxon Downy Woodpecker Hairy Woodpecker Northern Flicker
Class Aves Aves Aves
Order Piciformes Piciformes Piciformes
Family Picidae Picidae Picidae
Genus Picoides Picoides Colaptes
Species pubescens villosus auratus
Current Classification
• 29 orders
• 187 Families
• 2000+ Genera
• 10000+ species
• Rapidly changing
Biogeography (cont.)Regions Endemic (non-passerines) Representative Family Radiation
Holarctic
Incl. Nearctic and Palearctic
Loons, (Gaviidae)
Auks (Alcidae)
Accentors (Prunellidae)
NW warblers (Parulidae)
OW warblers (Sylviidae)
Neotropical Rheas (Rheidae)
Sunbittern (Eurypygidae)
Motmots (Momotidae)
Hummingbirds (Trochilidae)
Tyrant-flycatchers (Tyrannidae)
Ethiopian Ostrich (Struthionidae)
Turacos (Musophagidae)
Woodhoopoes (Phoeniculidae)
Larks (Alaudidae)
Sunbirds (Nectariniidae)
Oriental None Leafbirds (Irenidae)
Pheasants (Phasianidae)
Flowerpeckers (Dicaeidae)
Australasian Emus (Dromiceidae)
Kiwis (Apterygidae)
Monarch-flycatchers (Monarchidae)
Birds-of-paradise (Paradisaeidae)
Biogeography (cont.)
• Most bird communities or faunas are mosaics of species of various ages from various historical backgrounds
• + factors affecting species richness
LocalBird Community
RegionalBird Community
Speciation
Mass extinction events
Habitat selection
Immigration / Invasion Stochastic extinction events
Competitive exclusion
Predatory exclusion
From Ricklefs and Miller, 2000
Note on Phylogenetics
• Phylogenetics – History of the evolution of a group• Cladistics – defining groups based on shared
characteristics not found in ancestors (derived)• Cladogram – “tree-like” hypothesis of the hierarchical
evolutionary relationships of a groupA
B
C D E
time
FOTUsTipsNodesBranchesExtinct taxaSpeciation“Reading” the tree
Diversity of Birds100,000 species!
• Due to :1. Phyletic evolution
2. Cladistic evolution (speciation)
3. Extinction – “termination of a lineage”
a
b
c
Tim
e
a
b c
a
b a b c
a
d
- Heritable variation in a population due to mutation
- Some variation leads to differential reproductive success (if expressed)
Pg 47
Other features?
• Nucleated RBCs• Scales• Ankle in tarsal bones (not between long
bones and tarsals)• Bipedal (theropods)• Yolked, polar, cleidoic egg• Females are heterogametic• etc…
Link Between Birds and Reptiles
• Lots of morphological, behavioral and physiological similarity between Reptiles and Birds.
• Which reptiles???
Founding of Archaeopteryx
• Lithograph Quarrymen – Jurassic limestone • Single feather impression – 1861, Bavarian
Quarry• Complete skeletal impression – Few months
later• 2nd complete skeleton – 1877, quarry near
Eichstatt, Germany
• Herman von Meyer– Archaeopteryx lithographica
Archaeopteryx
• Debates
– Support of Darwinian evolution• Darwin predicted transitional fossils in 1859• ‘one of the best links between two taxa’ (Feduccia, Ostrom, etc.)
– Creation / Evolution debate (pg 27)
– Evolution of feathers (flight or insulation first?)
– Evolution of homeothermy in birds
– Evolution of flight• Ground-up vs. Trees down
The ‘historical’ evolution of flight debate
• Two main hypotheses:– Ground-up (cursorial hypothesis)– Trees-down (arboreal hypothesis)
Ground-up
• Assume biped, cursorial ancestor
• Has to be bipedal to use wings at all
• Large legs for running muscle attachment
• Bones of legs are long
• Once running:– Use feathers for other things
• Catch insects• Pick up minimum speed for lift: Flight
Trees-down
• Assume semi-bipedal leaping and gliding ancestor
• Use of claws to scale trees, then glide to ground• Claws retained in winged appendages• Short hand wing (power), relatively long arm
wing (lift)• Claw geometry (Feduccia’s study)• Large attachment sites for downstroke on
humerus but no keeled sternum• Flying squirrels?
Winner?
• Trees-down…maybe• Largely historical debate
• More productive???– Why evolve flight?
(1) To help escape from predators (2) To help catch flying or speedy prey(3) To help move from place to place (leaping or gliding)
• Vigilence• Migration, etc…• Nomadism
(4) To free the hindlegs for use as weapons
1/31/06
• Lab tomorrow – in the field (Briar Creek Lake)– Bring
• Clothes• Binoculars• Waterproof notebook• Time to meet?• Lab Activities BWSV• Read Taking Field Notes Handout
– Lecture Today• End Evolution• Start Form and Function
– Feathers
Leading alternative hypotheses
• Theropod Ancestry– Pros
• Lots of fossils– Some with feathers
• Bone morphology– Foot with 3 digits
» Embryology (birds w/5)– Sholder joint similarity
» Facilitates wings held at sides• Eggs in nest structure
– Cons• Theropod adapted for running (how
could flyer and runner share ancestry?
• Feathers? (Old argument)– Theropod fossils – yes – Used for insulation
» Exapted for flight.
• Thecodont Ancestry– Pros
• Tree dwellers– Glider forms– In the trees
• “More parsimonious argument that flight feathers evolved from gliding stabilizers rather than insulation”
– Cons• Fossil Evidence is missing
Feathers
• Most conspicuous integumental derivative
• Keratin
• Function– Flight– Heat Conservation
• Reduced convective and evaporative heat loss
• Increased insulation
Feather Development
• Development triggered by an interaction b/w epidermis and dermal mesenchyme
• Formation of dermal papilla (placode)
• Mitotic divisions in a collar zone of the stratum germinativum near the base of the papilla form a crown of barbs
• Covered by a horny sheath of epidermis
Lizard scales
Scaleless hen
Bird scales
Feather Development• As development proceeds:
– Differential cell division on one side of the papilla• Timing of expression of two proteins: Shh & Bmp2
– These cells form a shaft away from the body
• carrying the barbs that are formed in the collar
– The base of the feather recedes into the skin • Accompanied by layers of epithelial cells• Feather follicle
– Degeneration of epidermal sheath
Morphology of a feather (cont)
• Major Types:– Contour
• Insul., Flight• Vanes symmetrical• Vanes asymmetrical
– Semiplumes and • Rachis > barbs
– Down• Rachis < barbs• Insul.• Adult down• Natal down (lost)• Powder down
– Grooming– waterproofing
– Bristles• Little or no vane
– Filoplume• Monitor pennaceous
feathors• Attached to sensory
corpuscles
Plumulaceous
Pennaceous
Cross-section of feather follicle
1. Barb ridges of epithelial
2. Surrounding dermal core of connective tissue
3. Space of the follicle
4. Epithelial tissue of follicle
5. Associated musculature