Diversity and Classification
Birds share many characteristics with this prehistoric relative, including fused clavicles, feathers, hollow bones, and upright bipedal posture.
The primary mechanism of evolutionary change, this process is what determines which adaptations provide better fitness to an animal and which ones do not.
What is natural selection?
This waxy tube protects still-growing feathers and keeps them curled up.
What is a sheath?
This term, which is body mass divided by wing area, helps to determine flight capabilities along with aspect ratio.
What is wing loading?
Many birds have this large bone ridge running down the sternum, which serves as an extra attachment point for flight muscles in the pectorals.
What is a keel?
This group of birds was the earliest split in the avian phylogeny around 72 million years ago.
What is Paleognathe?
This form of evolutionary selection is primarily driven by both female preferences and competition among males.
What is sexual selection?
This process refers to the annual cycle of shedding old feathers and replacing them with new ones.
What is molting?
This term is used to describe wing curvature and asymmetry between the dorsal and ventral surfaces.
What is camber?
Unlike humans, who breathe with a diaphragm, birds use these to force air in and out of the lungs.
What are air sacs?
This clade evolved prior to the existence of landbirds, and includes many waterbird species such as grebes, sandpipers, gulls, and pelicans.
What is Aequorlitornithes?
This term is used to describe the natural selection condition that there must be competition among individuals for mates or survival.
What is differential reproductive success?
These colors in birds are produced by the refraction of light through the feathers, rather than being produced in the body.
What are structural colors?
A greater difference between wingspan to wing width, also known as this, makes more lift and less drag.
What is aspect ratio?
Bird eyes contain this third eyelid that both keeps in moisture and protects the eyes.
What is a nictitating membrane?
This clade contains many landbirds that may seem unrelated, including parrots, falcons, vultures, kingfisher, and toucans.
What is Inopinaves?
This form of speciation occurs when geographic isolation acts as a physical barrier to prevent species from intermingling.
What is allopatric speciation?
This structure in the epidermal collar will produce the rachis of feathers from keratin deposits.
What is the rachis ridge?
This version of powered flight, used primarily by hummingbirds, produces lift by downward-directed thrust.
What is hovering?
Located under the pectoralis, this muscle is connected to the sternum and provides power on the upstroke when it contracts.
What is the supracoracoideus?
A subclass of Order Passeriformes, this group of birds has a more developed syrinx than its sister group and contains a third of all bird species.
What is Oscines?
Females will select mates for both direct benefits, such as courtship feeding and good territory, and these types of benefits, such as "sexy sons" and avoiding inbreeding.
What are indirect benefits?
These feathers are entirely pennaceous, asymmetrical, and are attached directly to bone.
What are flight feathers?
This principle states that as air velocity increases, static pressure on a neighboring surface decreases.
What is Bernoulli's principle?
Birds have a two-part stomach, composed of the proventriculus with digestive enzymes and this, which is muscular and grinds up food with ingested "grit".
What is the gizzard?