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4 modes of air travel
- passive flight
- active flight
Dispersing spores (passive flight) evolved in the __ era
- Early Paleozoic
- Oldest spores = Ordovician
Insects with flight evolved in the __ period
Parachuting vertebrates evolved in the __ period and were diverse in the __ period
Pterosaurs evolved in the __ period.
Birds evolved in the __ period
Bats evolved in the __ period
Why did flight evolve in animals?
- escape predators
- catch prey
- move from place to place
- access to new food sources/unoccupied niche
- social reasons?
The first animals to fly were
- arthropods: flying Hexapods (common by late Carboniferous)
- flight only occurs in adults
origin of flight in insects
- possessed walking legs and exites (homologous with exopods?)
- evolved from gill/swimming legs
- didn't sacrifice "walking limb" for wings
In insects, wings were pre-adapted for
- Small wing aspect ratios require rapid strokes.
primary requirements/demands of active flight
- strong, yet light body (skeleton)
- streamline/aerodynamic body
- modified pectoral girdle capable of power stroke
- modified forelimb capable of supporting useful wing
Cursorial Flight Hypothesis among birds
- began by running and flapping from the ground
- Terrestrial theropods used wings to catch prey "insect nets" or
- flapping and fighting during social activities
- problem with hypothesis: Theropods could climb.
Arboreal Flight Hypothesis among birds
- began by climbing and jumping from trees
- Theropods climbs trees to avoid predation and forage
- problem with hypothesis: Climbing damages feathers on terrestrial theropods.
1st vertebrates capable of true/powered/active flight
Pterosaurs (Late Triassic)
locomotion of Pterosaurs on ground
- ability to walk is debatable:
- Fused pelvic girdle suggests bipedal locomotion.
- Scrawny hind limbs with "sideways" posture suggests quadrupedal locomotion
origin of birds
evolved by the Late Jurassic from Theropod dinosaurs
There was a low diversity of birds until the __ period
- late Cretaceous
- (very successful group)
A good candidate for sister taxa of birds are the
Dromeosaurids originated in the __ period
Late Cretaceous (younger than first birds)
Similarities between first birds and Dromeosaurids
- big brained
- terrestrial (couldn't fly)
general adaptations of birds
- hollow bones (pneumatic)
- keeled sternum
- short stout humerus
- wing supported by elongated radius and ulna
- fused clavicle AKA furculum
first "true bird"
Archaeopteryx (Late Jurassic)
similarities and differences between Archaeopteryx and modern birds
- similarities: feathers and furculum
- differences: fingers on wings, small sternum
purposes of developing wings
- display = social activity
characteristics of Archaopteryx that fit the Cursorial hypothesis
- tail feathers not for flight
- fused clavicle (furculum)
- claws for catching prey
characteristics of Archaopteryx that fit the Arboreal hypothesis
- retroverted hallux capable of perching
- fore limb clawed phalanges could be used for climbling
- Birds show a gradual increase in flying during early evolution.
- Later birds improved on the basic flight adaptations and become better flyers.
- Penguins and other divers use the basic stroke "flying underwater"
- Other birds use their feet for diving
The hypothetical ancestor of bats would have been
a nocturnal, insectivorous, arboreal glider
flight adaptations of bats
- keen senses (echolocation or good eyesight)
- modified pectoral girdle
- reduced radius with enlarged humerus and ulna
- clawed fingers
- uropatagium: membrane between hind limbs for stabilization and gliding
membrane supported by the arm and several elongated fingers, which help produce greater thrust
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