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Birds are
endothermic
Birds have two main types of feathers:
contour feathers and down feathers
The feathers on a wing are
flexible
The two types of flight feathers include
primary feathers and secondary feathers
Flapping of the entire wing occurs through
actions of the chest muscles (contraction of pectoralis muscles)
The flight muscles attach to a
blade-shaped keel projecting ventrally from the sternum
The flight muscles are rich with
oxygen-storing myoglobin
The frucula (fused clavicle) is
flexible enough to bend and provide support to the shoulder girdle during flapping
An important requirement for flight is
low body weight
Pneumatic bones
bones that are hollow rather than filled with tissue
The jaw in birds is lightened because
the teeth and beak are made of keratin
birds lack a ( ) bladder
urinary
In birds, uric acid is eliminated as
urate salts
Females of most bird species only posses one
functional (left) ovary
The air spaces of pneumatic bones can be connected to
air sacs
Airflow through bird lungs is
unidirectional
Ventilation is provided by
parabronchi (minimally expandable lungs)
Syrinx
voice box that resides near the junction of the trachea and bronchi
Birds typically have a ( ) neck and ( ) tail
elongate s-shaped; short (pygostyle)
The epidermis in birds is
very thin without sweat glands
The uropygial gland is essential to
preening
The nervous system in birds consists of
12 pairs of cranial nerves, very large cerebellum and optic lobes, single bone in the middle ear
Birds have a ( ) circulatory system with
closed; two atria and two ventricles
Birds belong to a group of diaspids known as
the archosaurs
Saurischia diverged into two groups:
Apatosaurs and theropods
Apatosaurs include
long-necked herbivorous dinosaurs
Theropods include
bipedal predators that gave rise to birds
The clade Neornithes includes the
avian crown group
Archaeopteryx
has the characteristics of both maniraptoran dinosaurs and modern birds
arboreal hypothesis
tree-dwelling precursors to modern birds jumped from branch to branch using their feathers for gliding before becoming fully capable of flapping flight
Terrestrial hypothesis
running was the stimulus for flight
Feathers provide ( ) which is beneficial for
insulation; thermoregulatory purposes when heat is being produced internally
Enantiornithes
dominant bird type in the cretaceous period
Orinthurae
became the dominant birds after the extinction of Enantiornithes
The three major clades of birds include:
Paleognathae, galloanserae, and neoaves
Paleognathae include
ostriches, emus, rheas, and kiwis
Galloanserae include
pheasants, ducks, geese, and swans
Neoaves include 5 clades:
Strisores, columbaves, gruiformes, aequorlitornithes, and inopinaves
Stirsores include
nightjars, swifts, and hummingbirds
Columbaves include
turacos, bustards, cuckoos, pigeons, and doves
Gruiforms include
cranes
Aequorlitornithes include
diving birds, wading birds, and shorebirds
Inopinaves include
hawks, owls, woodpeckers, parrots, falcons, crows, and songbirds